The Locator/ID Separation Protocol (LISP)lispers.netSan JoseCAUnited States of Americafarinacci@gmail.comvaf.net Internet Consultingvince.fuller@gmail.com1-4-5.netdmm@1-4-5.netCisco SystemsSan JoseCAUnited States of Americadarlewis@cisco.comUniversitat Politecnica de Catalunyac/ Jordi Girona s/nBarcelona08034Spainacabello@ac.upc.eduLISP data planeThis document describes the data plane protocol for the
Locator/ID Separation Protocol (LISP). LISP defines two
namespaces: Endpoint Identifiers (EIDs), which identify end hosts;
and Routing Locators (RLOCs), which identify network attachment
points. With this, LISP effectively separates control from data
and allows routers to create overlay networks. LISP-capable
routers exchange encapsulated packets according to EID-to-RLOC
mappings stored in a local Map-Cache.LISP requires no change to either host protocol stacks or
underlay routers and offers Traffic Engineering (TE),
multihoming, and mobility, among other features.This document obsoletes RFC 6830.Status of This Memo
This is an Internet Standards Track document.
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the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
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errata, and how to provide feedback on it may be obtained at
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Table of Contents
. Introduction
. Scope of Applicability
. Requirements Notation
. Definitions of Terms
. Basic Overview
. Deployment on the Public Internet
. Packet Flow Sequence
. LISP Encapsulation Details
. LISP IPv4-in-IPv4 Header Format
. LISP IPv6-in-IPv6 Header Format
. Tunnel Header Field Descriptions
. LISP EID-to-RLOC Map-Cache
. Dealing with Large Encapsulated Packets
. A Stateless Solution to MTU Handling
. A Stateful Solution to MTU Handling
. Using Virtualization and Segmentation with LISP
. Routing Locator Selection
. Routing Locator Reachability
. Echo-Nonce Algorithm
. EID Reachability within a LISP Site
. Routing Locator Hashing
. Changing the Contents of EID-to-RLOC Mappings
. Locator-Status-Bits
. Database Map-Versioning
. Multicast Considerations
. Router Performance Considerations
. Security Considerations
. Network Management Considerations
. Changes since RFC 6830
. IANA Considerations
. LISP UDP Port Numbers
. References
. Normative References
. Informative References
Acknowledgments
Authors' Addresses
IntroductionThis document describes the Locator/ID Separation
Protocol (LISP). LISP is an encapsulation protocol built around the
fundamental idea of separating the topological location of a network
attachment point from the node's identity . As a result, LISP creates two namespaces: Endpoint Identifiers
(EIDs), which are used to identify end hosts (e.g., nodes or Virtual
Machines); and routable Routing Locators (RLOCs), which are used to identify
network attachment points. LISP then defines functions for mapping
between the two namespaces and for encapsulating traffic
originated by devices using non-routable EIDs for transport across a
network infrastructure that routes and forwards using RLOCs. LISP
encapsulation uses a dynamic form of tunneling where no static provisioning
is required or necessary.LISP is an overlay protocol that separates control from data; this
document specifies the data plane as well as how LISP-capable
routers (Tunnel Routers) exchange packets by encapsulating them to
the appropriate location. Tunnel Routers are equipped with a cache,
called the Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache
is populated using the LISP control plane protocol .LISP does not require changes to either the host protocol stack or
underlay routers. By separating the EID from the RLOC space, LISP
offers native Traffic Engineering (TE), multihoming, and mobility, among
other features.Creation of LISP was initially motivated by discussions during
the IAB-sponsored Routing and Addressing Workshop held in Amsterdam
in October 2006 (see ).This document specifies the LISP data plane encapsulation and
other LISP forwarding node functionality while specifies the LISP control
plane. LISP deployment guidelines can be found in , and describes
considerations for network operational management. Finally, describes the LISP architecture.This document obsoletes RFC 6830.Scope of ApplicabilityLISP was originally developed to address the Internet-wide
route scaling problem .
While there are a number of approaches of
interest for that problem, as LISP has been developed and refined, a
large number of other ways to use LISP have been found and are being
implemented. As such, the design and development of
LISP have changed so as to focus on these use cases. The common
property of these uses is a large set of cooperating entities
seeking to communicate over the public Internet or other large
underlay IP infrastructures while keeping the addressing and
topology of the cooperating entities separate from the underlay
and Internet topology, routing, and addressing.Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14
when, and only when, they appear in all capitals, as shown here.
Definitions of Terms
Address Family Identifier (AFI):
"AFI" is a term used
to describe an address encoding in a packet. An address family is an address
format found in data plane packet headers,
for example, an IPv4 address or an IPv6 address. See , , , and for details. An AFI
value of 0 used in this specification indicates an unspecified
encoded address where the length of the address is 0 octets
following the 16-bit AFI value of 0.
Anycast Address:
"Anycast address" refers to the same
IPv4 or IPv6 address configured
and used on multiple systems at the same time. An EID or RLOC can
be an anycast address in each of their own address spaces.
Client-side:
"Client-side" is a term used in this
document to indicate a connection initiation attempt by an end-system
represented by an EID.
Egress Tunnel Router (ETR):
An ETR is a router that
accepts an IP packet where the destination address in the "outer"
IP header is one of its own RLOCs. The router strips the "outer"
header and forwards the packet based on the next IP header
found. In general, an ETR receives LISP-encapsulated IP packets
from the Internet on one side and sends decapsulated IP packets to
site end-systems on the other side. ETR functionality does not
have to be limited to a router device. A server host can be the
endpoint of a LISP tunnel as well.
EID-to-RLOC Database:
The EID-to-RLOC Database is a
distributed database that contains all known EID-Prefix-to-RLOC
mappings. Each potential ETR typically contains a small piece of
the database: the EID-to-RLOC mappings for the EID-Prefixes
"behind" the router. These map to one of the router's own IP
addresses that are routable on the underlay.
Note that there MAY be transient conditions when the EID-Prefix
for the LISP site and Locator-Set for each EID-Prefix may not be the
same on all ETRs. This has no negative implications, since a
partial set of Locators can be used.
EID-to-RLOC Map-Cache:
The EID-to-RLOC Map-Cache is a
generally short-lived, on-demand table in an Ingress Tunnel Router (ITR) that stores, tracks, and
is responsible for timing out and otherwise validating EID-to-RLOC
mappings. This cache is distinct from the full "database" of
EID-to-RLOC mappings; it is dynamic, local to the ITR(s), and
relatively small, while the database is distributed, relatively
static, and much more widely scoped to LISP nodes.
EID-Prefix:
An EID-Prefix is a power-of-two block
of EIDs that are allocated to a site by an address allocation
authority. EID-Prefixes are associated with a set of RLOC
addresses. EID-Prefix allocations can be broken up into smaller
blocks when an RLOC-Set is to be associated with the larger
EID-Prefix block.
End-System:
An end-system is an IPv4 or IPv6 device
that originates packets with a single IPv4 or IPv6 header. The
end-system supplies an EID value for the destination address field
of the IP header when communicating outside of its routing domain.
An end-system can be a host computer, a switch or router device,
or any network appliance.
Endpoint ID (EID):
An EID is a 32-bit (for IPv4) or
128-bit (for IPv6) value that identifies a host. EIDs are generally
only found in the source and destination
address fields of the first (innermost) LISP header of a
packet. The host obtains a destination
EID through a Domain Name System (DNS)
lookup or Session Initiation Protocol (SIP) exchange. This
behavior does not change when LISP is in use. The
source EID is obtained via existing mechanisms used to set a
host's "local" IP address. An EID used on the public Internet MUST
have the same properties as any other IP address used in that
manner; this means, among other things, that it MUST be
unique. An EID is allocated to a host from an EID-Prefix block
associated with the site where the host is located. An EID can be
used by a host to refer to other hosts. Note that EID blocks MAY
be assigned in a hierarchical manner, independent of the network
topology, to facilitate scaling of the mapping database. In
addition, an EID block assigned to a site MAY have site-local
structure (subnetting) for routing within the site; this structure
is not visible to the underlay routing system. In theory, the bit
string that represents an EID for one device can represent an RLOC
for a different device. When discussing other Locator/ID separation proposals, any
references to an EID in this document will refer to a LISP EID.
Ingress Tunnel Router (ITR):
An ITR is a router
that resides in a LISP site. Packets sent by sources inside of the
LISP site to destinations outside of the site are candidates for
encapsulation by the ITR. The ITR treats the IP destination
address as an EID and performs an EID-to-RLOC mapping lookup. The
router then prepends an "outer" IP header with one of its routable
RLOCs (in the RLOC space) in the source address field and the
result of the mapping lookup in the destination address field.
Note that this destination RLOC may be an intermediate, proxy
device that has better knowledge of the EID-to-RLOC mapping closer
to the destination EID. In general, an ITR receives IP packets
from site end-systems on one side and sends LISP-encapsulated IP
packets toward the Internet on the other side.
LISP Header:
"LISP header" is a term used in this document to refer
to the outer IPv4 or IPv6 header, a UDP header, and a LISP-
specific 8-octet header, all of which follow the UDP header. An
ITR prepends LISP headers on packets, and an ETR strips them.
LISP Router:
A LISP router is a router that
performs the functions of any or all of the following: ITRs, ETRs, Re-encapsulating Tunneling Routers (RTRs),
Proxy-ITRs (PITRs), or Proxy-ETRs (PETRs).
LISP Site:
A LISP site is a set of routers in an edge
network that are under a single technical administration. LISP
routers that reside in the edge network are the demarcation points
to separate the edge network from the core network.
Locator-Status-Bits (LSBs):
Locator-Status-Bits are
present in the LISP header. They are used by ITRs to inform ETRs
about the up/down status of all ETRs at the local site. These bits
are used as a hint to convey up/down router status and not path
reachability status. The LSBs can be verified by use of one of the
Locator reachability algorithms described in . An ETR MUST rate limit the action it takes
when it detects changes in the Locator-Status-Bits.
Proxy-ETR (PETR):
A PETR is defined and described
in . A PETR acts like an ETR but does so
on behalf of LISP sites that send packets to destinations at
non-LISP sites.
Proxy-ITR (PITR):
A PITR is defined and described
in . A PITR acts like an ITR but does so
on behalf of non-LISP sites that send packets to destinations at
LISP sites.
Recursive Tunneling:
Recursive Tunneling occurs
when a packet has more than one LISP IP header. Additional layers
of tunneling MAY be employed to implement Traffic Engineering or
other rerouting as needed. When this is done, an additional
"outer" LISP header is added, and the original RLOCs are preserved
in the "inner" header.
Re-encapsulating Tunneling Router (RTR):
An RTR acts like an ETR to remove a LISP header, then acts as an
ITR to prepend a new LISP header. This is known as
Re-encapsulating Tunneling. Doing this allows a packet to be
rerouted by the RTR without adding the overhead of additional
tunnel headers. When using multiple mapping database systems, care
must be taken to not create re-encapsulation loops through
misconfiguration.
Route-Returnability:
Route-returnability is an
assumption that the underlying routing system will deliver packets
to the destination. When combined with a nonce that is provided by
a sender and returned by a receiver, this limits off-path data
insertion. A route-returnability check is verified when a message
is sent with a nonce, another message is returned with the same
nonce, and the destination of the original message appears as the
source of the returned message.
Routing Locator (RLOC):
An RLOC is an IPv4 address or IPv6 address of
an Egress Tunnel Router (ETR). An RLOC is the output of an
EID-to-RLOC mapping lookup. An EID maps to zero or more
RLOCs. Typically, RLOCs are numbered from blocks that
are assigned to a site at each point to which it attaches to the
underlay network, where the topology is defined by the connectivity
of provider networks. Multiple RLOCs can be assigned to the same
ETR device or to multiple ETR devices at a site.
Server-side:
"Server-side" is a term used in this
document to indicate that a connection initiation attempt is being
accepted for a destination EID.
xTR:
An xTR is a reference to an ITR or ETR when
direction of data flow is not part of the context description.
"xTR" refers to the router that is the tunnel endpoint and is used
synonymously with the term "Tunnel Router". For example, "An xTR
can be located at the Customer Edge (CE) router" indicates both
ITR and ETR functionality at the CE router.
Basic OverviewOne key concept of LISP is that end-systems operate the same way
when LISP is not in use as well as when LISP is in use. The IP addresses that
hosts use for tracking sockets
and connections, and for sending and receiving packets, do not
change. In LISP terminology, these IP addresses are called Endpoint
Identifiers (EIDs).Routers continue to forward packets based on IP destination
addresses. When a packet is LISP encapsulated, these addresses are
referred to as RLOCs. Most routers along a path
between two hosts will not change; they continue to perform
routing/forwarding lookups on the destination addresses. For routers
between the source host and the ITR as well as routers from the ETR
to the destination host, the destination address is an EID. For the
routers between the ITR and the ETR, the destination address is an
RLOC.Another key LISP concept is the "Tunnel Router". A Tunnel Router
prepends LISP headers on host-originated packets and strips them
prior to final delivery to their destination. The IP addresses in
this "outer header" are RLOCs. During end-to-end packet
exchange between two Internet hosts, an ITR prepends a new LISP
header to each packet, and an ETR strips the new header. The ITR
performs EID-to-RLOC lookups to determine the routing path to the
ETR, which has the RLOC as one of its IP addresses. Some basic rules governing LISP are:
End-systems only send to addresses that are EIDs. EIDs are
typically IP addresses assigned to hosts (other types of EIDs are
supported by LISP; see for further
information). End-systems don't know that addresses are EIDs
versus RLOCs but assume that packets get to their intended
destinations. In a system where LISP is deployed, LISP routers
intercept EID-addressed packets and assist in delivering them
across the network core where EIDs cannot be routed. The
procedure a host uses to send IP packets does not change.
LISP routers prepend and strip outer headers with RLOC addresses. See for details.
RLOCs are always IP addresses assigned to routers, preferably
topologically oriented addresses from provider Classless
Inter-Domain Routing (CIDR) blocks.
When a router originates packets, it MAY use as a source
address either an EID or RLOC. When acting as a host (e.g., when
terminating a transport session such as Secure Shell (SSH),
TELNET, or the Simple Network Management Protocol (SNMP)), it
MAY use an EID that is explicitly assigned for that purpose. An
EID that identifies the router as a host MUST NOT be used as an
RLOC; an EID is only routable within the scope of a site. A
typical BGP configuration might demonstrate this "hybrid"
EID/RLOC usage where a router could use its "host-like" EID to
terminate internal BGP (iBGP) sessions to other routers in a site while at the
same time using RLOCs to terminate external BGP (eBGP) sessions to routers
outside the site.
Packets with EIDs in them are not expected to be delivered
end to end in the absence of an EID-to-RLOC mapping
operation. They are expected to be used locally for intra-site
communication or to be encapsulated for inter-site
communication.
EIDs MAY also be structured (subnetted) in a manner suitable
for local routing within an Autonomous System (AS).
An additional LISP header MAY be prepended to packets by a
TE-ITR when rerouting of the path for a packet is desired. A
potential use case for this would be an ISP router that needs to
perform Traffic Engineering for packets flowing through its
network. In such a situation, termed "Recursive Tunneling", an ISP
transit acts as an additional ITR, and the destination RLOC it
uses for the new prepended header would be either a TE-ETR within
the ISP (along an intra-ISP traffic-engineered path) or a TE-ETR
within another ISP (an inter-ISP traffic-engineered path, where an
agreement to build such a path exists). In order to avoid excessive packet overhead as well as possible
encapsulation loops, it is RECOMMENDED that a maximum of two
LISP headers can be prepended to a packet. For initial LISP
deployments, it is assumed that two headers is sufficient, where
the first prepended header is used at a site for separation of location and identity and the second prepended header is used inside a
service provider for Traffic Engineering purposes.Tunnel Routers can be placed fairly flexibly in a multi-AS
topology. For example, the ITR for a particular end-to-end packet
exchange might be the first-hop or default router within a site
for the source host. Similarly, the ETR might be the last-hop
router directly connected to the destination host. As another
example, perhaps for a VPN service outsourced to an ISP by a site,
the ITR could be the site's border router at the service
provider attachment point. Mixing and matching of site-operated,
ISP-operated, and other Tunnel Routers is allowed for maximum
flexibility. Deployment on the Public InternetSeveral of the mechanisms in this document are intended for deployment in controlled,
trusted environments and are insecure for use over the public Internet.
In particular, on the public Internet, xTRs:
MUST set the N-, L-, E-, and V-bits in the LISP header () to zero.
MUST NOT use Locator-Status-Bits and Echo-Nonce, as described in , for RLOC reachability.
Instead, they MUST rely solely on control plane methods.
MUST NOT use gleaning or Locator-Status-Bits and Map-Versioning, as described in , to update the EID-to-RLOC mappings.
Instead, they MUST rely solely on control plane methods.
Packet Flow SequenceThis section provides an example of the unicast packet flow,
also including control plane information as specified in . The example also assumes
the following conditions:
Source host "host1.abc.example.com" is sending a
packet to "host2.xyz.example.com", exactly as it would if the site was
not using LISP.
Each site is multihomed, so each Tunnel Router has an
address (RLOC) assigned from the service provider address
block for each provider to which that particular Tunnel Router
is attached.
The ITR(s) and ETR(s) are directly connected to the source
and destination, respectively, but the source and destination
can be located anywhere in the LISP site.
A Map-Request is sent for an external destination when the
destination is not found in the forwarding table or matches a
default route. Map-Requests are sent to the mapping database
system by using the LISP control plane protocol documented in
.
Map-Replies are sent on the underlying routing system
topology, using the
control plane protocol .
Client host1.abc.example.com wants to communicate with
server host2.xyz.example.com:
host1.abc.example.com wants to open a TCP connection to
host2.xyz.example.com. It does a DNS lookup on
host2.xyz.example.com. An A/AAAA record is returned. This
address is the destination EID. The locally assigned address
of host1.abc.example.com is used as the source EID. An IPv4
or IPv6 packet is built and forwarded through the LISP site
as a normal IP packet until it reaches a LISP ITR.
The LISP ITR must be able to map the destination EID to an
RLOC of one of the ETRs at the destination site. A method
for doing this is to send a LISP Map-Request, as specified in
.
The Mapping System helps forward the Map-Request to the
corresponding ETR. When the Map-Request arrives at one of the
ETRs at the destination site, it will process the packet as a
control message.
The ETR looks at the destination EID of the Map-Request
and matches it against the prefixes in the ETR's configured
EID-to-RLOC mapping database. This is the list of
EID-Prefixes the ETR is supporting for the site it resides
in. If there is no match, the Map-Request is
dropped. Otherwise, a LISP Map-Reply is returned to the
ITR.
The ITR receives the Map-Reply message, parses the message,
and stores the mapping information from the packet. This information
is stored in the ITR's EID-to-RLOC Map-Cache. Note that the
Map-Cache is an on-demand cache. An ITR will manage its
Map-Cache in such a way that optimizes for its resource
constraints.
Subsequent packets from host1.abc.example.com to
host2.xyz.example.com will have a LISP header prepended by
the ITR using the appropriate RLOC as the LISP header
destination address learned from the ETR. Note that the
packet MAY be sent to a different ETR than the one that
returned the Map-Reply due to the source site's hashing
policy or the destination site's Locator-Set policy.
The ETR receives these packets directly (since the
destination address is one of its assigned IP addresses),
checks the validity of the addresses, strips the LISP header,
and forwards packets to the attached destination host.
In order to defer the need for a mapping lookup in the
reverse direction, it is OPTIONAL for an ETR to
create a cache entry
that maps the source EID (inner-header source IP address) to
the source RLOC (outer-header source IP address) in a
received LISP packet. Such a cache entry is termed a
"glean mapping" and only contains a single RLOC for the EID
in question. More complete information about additional
RLOCs SHOULD be verified by sending a LISP Map-Request for
that EID. Both the ITR and the ETR MAY also influence the
decision the other makes in selecting an RLOC.
LISP Encapsulation DetailsSince additional tunnel headers are prepended, the packet
becomes larger and can exceed the MTU of any link traversed from
the ITR to the ETR. It is RECOMMENDED in IPv4 that packets do not
get fragmented as they are encapsulated by the ITR. Instead, the
packet is dropped and an ICMPv4 Unreachable / Fragmentation Needed
message is returned to the source.In the case when fragmentation is needed, it is
RECOMMENDED that implementations provide support for one of the
proposed fragmentation and reassembly schemes. Two existing
schemes are detailed in .Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the
LISP architecture supports IPv4 EIDs with IPv6 RLOCs (where the
inner header is in IPv4 packet format and the outer header is in
IPv6 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner
header is in IPv6 packet format and the outer header is in IPv4
packet format). The next sub-sections illustrate packet formats
for the homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all
4 combinations MUST be supported. Additional types of EIDs are
defined in .As LISP uses UDP encapsulation to carry traffic between xTRs
across the Internet, implementors should be aware of the
provisions of , especially those given in its
Section on congestion control for UDP tunneling.Implementors are encouraged to consider UDP checksum usage
guidelines in when it is
desirable to protect UDP and LISP headers against corruption.LISP IPv4-in-IPv4 Header Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL | DSCP |ECN| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OH | Time to Live | Protocol = 17 | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source Routing Locator |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|R|K|K| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL | DSCP |ECN| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IH | Time to Live | Protocol | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source EID |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IHL = IP-Header-Length
LISP IPv6-in-IPv6 Header Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| DSCP |ECN| Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Payload Length | Next Header=17| Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
O + +
u | |
t + Source Routing Locator +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination Routing Locator +
| | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|R|K|K| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| DSCP |ECN| Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Payload Length | Next Header | Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
I + +
n | |
n + Source EID +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination EID +
\ | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Tunnel Header Field Descriptions
Inner Header (IH):
The inner header is the header on the datagram
received from the originating host . The
source and destination IP addresses are EIDs.
Outer Header (OH):
The outer header is a new
header prepended by an ITR. The address fields contain RLOCs
obtained from the ingress router's EID-to-RLOC Map-Cache. The IP
protocol number is "UDP (17)" from . The setting of the Don't Fragment (DF)
bit 'Flags' field is according to rules listed in Sections
and .
UDP Header:
The UDP header contains an ITR-selected source port when encapsulating a packet. See for details on the hash algorithm used
to select a source port based on the 5-tuple of the inner
header. The destination port MUST be set to the well-known
IANA-assigned port value 4341.
UDP Checksum:
The 'UDP Checksum' field SHOULD
be transmitted as zero by an ITR for either IPv4 or IPv6 encapsulation . When a
packet with a zero UDP checksum is received by an ETR, the
ETR MUST accept the packet for decapsulation. When an ITR
transmits a non-zero value for the UDP checksum, it MUST
send a correctly computed value in this field. When an ETR
receives a packet with a non-zero UDP checksum, it MAY
choose to verify the checksum value. If it chooses to
perform such verification and the verification fails, the
packet MUST be silently dropped. If the ETR either chooses not to
perform the verification or performs the verification
successfully, the packet MUST be accepted for
decapsulation. The handling of UDP zero checksums over IPv6
for all tunneling protocols, including LISP, is subject to
the applicability statement in .
UDP Length:
The 'UDP Length' field is set for
an IPv4-encapsulated packet to be the sum of the
inner-header IPv4 Total Length plus the UDP and LISP header
lengths. For an IPv6-encapsulated packet, the 'UDP Length'
field is the sum of the inner-header IPv6 Payload Length,
the size of the IPv6 header (40 octets), and the size of the
UDP and LISP headers.
N:
The N-bit is the nonce-present bit. When
this bit is set to 1, the low-order 24 bits of the first 32
bits of the LISP header contain a nonce. See for details. Both N- and V-bits MUST NOT be set in the same packet. If they are, a decapsulating
ETR MUST treat the 'Nonce/Map-Version' field as having a
nonce value present.
L:
The L-bit is the 'Locator-Status-Bits'
field enabled bit. When this bit is set to 1, the
Locator-Status-Bits in the second 32 bits of the LISP
header are in use.
x 1 x x 0 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E:
The E-bit is the Echo-Nonce-request bit.
This bit MUST be ignored and has no meaning when the N-bit
is set to 0. When the N-bit is set to 1 and this bit is set
to 1, an ITR is requesting that the nonce value in the
'Nonce' field be echoed back in LISP-encapsulated packets
when the ITR is also an ETR. See
for details.
V:
The V-bit is the Map-Version present
bit. When this bit is set to 1, the N-bit MUST be 0. Refer
to for more details on Database Map-Versioning. This
bit indicates that the LISP header is encoded in this
case as:
0 x 0 1 x x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID/Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I:
The I-bit is the Instance ID bit. See for more details. When this bit is set
to 1, the 'Locator-Status-Bits' field is reduced to 8 bits
and the high-order 24 bits are used as an Instance ID. If
the L-bit is set to 0, then the low-order 8 bits are
transmitted as zero and ignored on receipt. The format of
the LISP header would look like this:
x x x x 1 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID | LSBs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R:
The R-bit is a reserved and unassigned bit
for future use. It MUST be set to 0 on transmit and MUST be
ignored on receipt.
KK:
The KK-bits are a 2-bit field used when
encapsulated packets are encrypted. The field is set to 00
when the packet is not encrypted. See for further information.
LISP Nonce:
The LISP 'Nonce' field is a 24-bit
value that is randomly generated by an ITR when the N-bit is
set to 1. Nonce generation algorithms are an implementation
matter but are required to generate different nonces when
sending to different RLOCs. The nonce is also used when the E-bit is set to
request the nonce value to be echoed by the other side when
packets are returned. When the E-bit is clear but the N-bit
is set, a remote ITR is either echoing a previously
requested Echo-Nonce or providing a random nonce. See for more details. Finally, when
both the N- and V-bits are not set (N=0, V=0), then both the 'Nonce'
and 'Map-Version' fields are set to 0 and ignored on receipt.
LISP Locator-Status-Bits (LSBs):
When the
L-bit is also set, the 'Locator-Status-Bits' field in the
LISP header is set by an ITR to indicate to an ETR the
up/down status of the Locators in the source site. Each RLOC
in a Map-Reply is assigned an ordinal value from 0 to n-1
(when there are n RLOCs in a mapping entry). The
Locator-Status-Bits are numbered from 0 to n-1 from the
least significant bit of the field. The field is 32 bits
when the I-bit is set to 0 and is 8 bits when the I-bit is
set to 1. When a Locator-Status-Bit is set to 1, the ITR is
indicating to the ETR that the RLOC associated with the bit
ordinal has up status. See for
details on how an ITR can determine the status of the ETRs
at the same site. When a site has multiple EID-Prefixes
that result in multiple mappings (where each could have a
different Locator-Set), the Locator-Status-Bits setting in
an encapsulated packet MUST reflect the mapping for the
EID-Prefix that the inner-header source EID address
matches (longest-match). If the LSB for an anycast Locator is set to 1, then
there is at least one RLOC with that address, and the ETR is
considered 'up'.
When doing ITR/PITR encapsulation:
The outer-header 'Time to Live' field (or 'Hop Limit'
field, in the case of IPv6) SHOULD be copied from the
inner-header 'Time to Live' field.
The outer-header IPv4 'Differentiated Services Code Point
(DSCP)' field (or 'Traffic Class' field, in the case of
IPv6) SHOULD be copied from the inner-header IPv4 'DSCP' field (or
'Traffic Class' field, in the case of IPv6) to the
outer header. Guidelines for this can be found in .
The IPv4 'Explicit Congestion Notification (ECN)' field and bits
6 and 7 of the IPv6 'Traffic Class' field require special
treatment in order to avoid discarding indications of
congestion as specified in .
When doing ETR/PETR decapsulation:
The inner-header IPv4 'Time to Live' field (or 'Hop Limit'
field, in the case of IPv6) MUST be copied from the
outer-header 'Time to Live'/'Hop Limit' field when the Time to Live / Hop Limit
value of the outer header is less than the Time to Live / Hop Limit
value of the inner header. Failing to perform this check
can cause the Time to Live / Hop Limit of the inner header to increment
across encapsulation/decapsulation cycles. This check is
also performed when doing initial encapsulation, when a
packet comes to an ITR or PITR destined for a LISP site.
The outer-header IPv4 'Differentiated Services Code Point
(DSCP)' field (or 'Traffic Class' field, in the case of
IPv6) SHOULD be copied from the outer-header 'IPv4 DSCP' field (or
'Traffic Class' field, in the case of IPv6) to the
inner header. Guidelines for this can be found in .
The IPv4 'Explicit Congestion Notification (ECN)' field and bits
6 and 7 of the IPv6 'Traffic Class' field require special
treatment in order to avoid discarding indications of
congestion as specified in . Note
that implementations exist that copy the 'ECN' field from
the outer header to the inner header, even though does not recommend this behavior. It is
RECOMMENDED that implementations change to support the
behavior discussed in .
Note that if an ETR/PETR is also an ITR/PITR and chooses to
re-encapsulate after decapsulating, the net effect of this
is that the new outer header will carry the same Time to
Live as the old outer header minus 1.Copying the Time to Live serves two purposes:
first, it preserves the distance the host intended the packet to
travel; second, and more importantly, it provides for
suppression of looping packets in the event there is a loop of
concatenated tunnels due to misconfiguration. Some xTRs, PETRs, and PITRs perform re-encapsulation operations and
need to treat ECN functions in a special way. Because the re-encapsulation
operation is a
sequence of two operations, namely a decapsulation followed by
an encapsulation, the ECN bits MUST be treated as described
above for these two operations.
The LISP data plane protocol is not backwards compatible with
and does not have explicit support for introducing
future protocol changes (e.g., an explicit version field). However,
the LISP control plane allows an ETR to register
data plane capabilities by means of new LISP Canonical Address Format (LCAF) types .
In this way, an ITR can be made aware of the data plane capabilities
of an ETR and encapsulate accordingly. The specification of the new
LCAF types, the new LCAF mechanisms, and their use are out of the
scope of this document.
LISP EID-to-RLOC Map-CacheITRs and PITRs maintain an on-demand cache, referred to as the LISP
EID-to-RLOC Map-Cache, that contains mappings from EID-Prefixes
to Locator-Sets. The cache is used to encapsulate packets from
the EID space to the corresponding RLOC network attachment point.When an ITR/PITR receives a packet from inside of the LISP
site to destinations outside of the site, a longest-prefix match
lookup of the EID is done to the Map-Cache.When the lookup succeeds, the Locator-Set retrieved from the
Map-Cache is used to send the packet to the EID's topological
location.If the lookup fails, the ITR/PITR needs to retrieve the
mapping using the LISP control plane protocol . While the mapping is being retrieved,
the ITR/PITR can either drop or buffer the packets. This document does not have specific
recommendations about the action to be taken.
It is up to the deployer to consider whether or not it is desirable to buffer packets
and deploy a LISP implementation that offers the desired behavior. Once the mapping is resolved,
it is then stored in the local Map-Cache to forward subsequent packets addressed to
the same EID-Prefix.The Map-Cache is a local cache of mappings; entries are
expired based on the associated Time to Live. In addition,
entries can be updated with more current information; see for further information on
this. Finally, the Map-Cache also contains reachability
information about EIDs and RLOCs and uses LISP reachability
information mechanisms to determine the reachability of RLOCs;
see for the specific mechanisms.Dealing with Large Encapsulated PacketsThis section proposes two mechanisms to deal with
packets that exceed the Path MTU (PMTU) between the ITR and ETR.It is left to the implementor to decide if the stateless or
stateful mechanism SHOULD be implemented. Both or neither can be
used, since it is a local decision in the ITR regarding how
to deal with MTU issues, and sites can interoperate with differing
mechanisms.Both stateless and stateful mechanisms also apply to
Re-encapsulating and Recursive Tunneling, so any actions
below referring to an ITR also apply to a TE-ITR.A Stateless Solution to MTU HandlingAn ITR stateless solution to handle MTU issues is described as
follows:
Define H to be the size, in octets, of the outer header an ITR
prepends to a packet. This includes the UDP and LISP header lengths.
Define L to be the size, in octets, of the maximum-sized packet
an ITR can send to an ETR without the need for the ITR or any
intermediate routers to fragment the packet.
The network administrator of the LISP deployment has to determine
what the suitable value of L is, so as to make sure that no MTU issues arise.
Define an architectural constant S for the maximum size of a
packet, in octets, an ITR MUST receive from the source so the
effective MTU can be met. That is, L = S + H.
When an ITR receives a packet from a site-facing interface and
adds H octets worth of encapsulation to yield a packet size
greater than L octets (meaning the received packet size was
greater than S octets from the source), it resolves the MTU issue
by first splitting the original packet into 2 equal-sized
fragments. A LISP header is then prepended to each fragment. The
size of the encapsulated fragments is then (S/2 + H), which is
less than the ITR's estimate of the PMTU between the ITR and
its correspondent ETR.When an ETR receives encapsulated fragments, it treats them
as two individually encapsulated packets. It strips the LISP
headers and then forwards each fragment to the destination host of
the destination site. The two fragments are reassembled at
the destination host into the single IP datagram that was
originated by the source host. Note that reassembly can happen
at the ETR if the encapsulated packet was fragmented at or after the
ITR.This behavior MUST be implemented by the ITR only when the source
host originates a packet with the 'DF' field of the IP header set
to 0. When the 'DF' field of the IP header is set to 1 or the
packet is an IPv6 packet originated by the source host, the ITR
will drop the packet when the size (adding in the size of the
encapsulation header) is greater than L and send an ICMPv4
Unreachable / Fragmentation Needed or ICMPv6 Packet Too Big (PTB)
message to the source with a value of S, where S is (L - H).When the outer-header encapsulation uses an IPv4 header, an
implementation SHOULD set the DF bit to 1 so ETR fragment
reassembly can be avoided. An implementation MAY set the DF
bit in such headers to 0 if it has good reason to believe
there are unresolvable PMTU issues between the sending ITR
and the receiving ETR.It is RECOMMENDED that L be defined as 1500.
Additional information about in-network MTU and fragmentation issues can be found in .A Stateful Solution to MTU HandlingAn ITR stateful solution to handle MTU issues is described as
follows:
The ITR will keep state of the effective MTU for each Locator
per Map-Cache entry. The effective MTU is what the core network
can deliver along the path between the ITR and ETR.
When an IPv4-encapsulated packet with the DF bit set to 1 exceeds what the core network
can deliver, one of the intermediate routers on the path will
send an ICMPv4
Unreachable / Fragmentation Needed message to the ITR. The
ITR will parse the ICMP message to determine which Locator is
affected by the effective MTU change and then record the new
effective MTU value in the Map-Cache entry.
When a packet is received by the ITR from a source inside
of the site and the size of the packet is greater than the
effective MTU stored with the Map-Cache entry associated with
the destination EID the packet is for, the ITR will send an
ICMPv4 Unreachable / Fragmentation Needed message back to the source. The packet size
advertised by the ITR in the ICMP message is the effective
MTU minus the LISP encapsulation length.
Even though this mechanism is stateful, it has advantages over
the stateless IP fragmentation mechanism, by not involving the
destination host with reassembly of ITR fragmented packets.Please note that using ICMP packets for PMTU discovery, as described
in and , can result in suboptimal behavior in the
presence of ICMP packet losses or off-path attackers that spoof ICMP.
Possible mitigations include ITRs and ETRs cooperating on MTU probe
packets or ITRs
storing the beginning of large packets to verify that they match
the echoed packet in an ICMP Fragmentation Needed / PTB message.Using Virtualization and Segmentation with LISPThere are several cases where segregation is needed at the
EID level. For instance, this is the case for deployments
containing overlapping addresses, traffic isolation policies,
or multi-tenant virtualization. For these and other scenarios
where segregation is needed, Instance IDs are used.An Instance ID can be carried in a LISP-encapsulated
packet. An ITR that prepends a LISP header will copy a
24-bit value used by the LISP router to uniquely identify
the address space. The value is copied to the 'Instance ID'
field of the LISP header, and the I-bit is set to 1.When an ETR decapsulates a packet, the Instance ID from the
LISP header is used as a table identifier to locate the
forwarding table to use for the inner destination EID
lookup.For example, an 802.1Q VLAN tag or VPN identifier could be
used as a 24-bit Instance ID. See
for details regarding LISP VPN use cases. Please note that the Instance ID
is not protected; an on-path attacker can modify the tags and, for instance,
allow communications between logically isolated VLANs.Participants within a LISP deployment must agree
on the meaning of Instance ID values. The source and destination EIDs
MUST belong to the same Instance ID.
The Instance ID SHOULD NOT be used with overlapping IPv6 EID addresses.Routing Locator SelectionThe Map-Cache contains the state used by ITRs and PITRs to
encapsulate packets. When an ITR/PITR receives a packet from
inside the LISP site to a destination outside of the site, a
longest-prefix match lookup of the EID is done to the
Map-Cache (see ). The lookup
returns a single Locator-Set containing a list of RLOCs
corresponding to the EID's topological location. Each RLOC in
the Locator-Set is associated with a Priority and Weight;
this information is used to select the RLOC to
encapsulate.The RLOC with the lowest Priority is selected. An RLOC
with Priority 255 means that it MUST NOT be used for
forwarding. When multiple RLOCs have the same Priority, then
the Weight states how to load-balance traffic among them.
The value of the Weight represents the relative weight of
the total packets that match the mapping entry.The following are different scenarios for choosing
RLOCs and the controls that are available:
The server-side returns one RLOC. The client-side can only
use one RLOC. The server-side has complete control of the
selection.
The server-side returns a list of RLOCs where a subset
of the list has the same best Priority. The client can only use
the subset list according to the
weighting assigned by the server-side. In this case, the
server-side controls both the subset list and load splitting
across its members. The client-side can use RLOCs outside
of the subset list if it determines that the subset
list is unreachable (unless RLOCs are set to a Priority of 255).
Some sharing of control exists: the server-side determines
the destination RLOC list and load distribution while the
client-side has the option of using alternatives to this list if
RLOCs in the list are unreachable.
The server-side sets a Weight of zero for the RLOC subset
list. In this case, the client-side can choose how the traffic
load is spread across the subset list. See for details on load-sharing mechanisms.
Control is shared by the server-side determining the list and
the client-side determining load distribution. Again, the
client can use alternative RLOCs if the server-provided list
of RLOCs is unreachable.
Either side (more likely the server-side ETR) decides to "glean"
the RLOCs. For example, if the server-side ETR gleans RLOCs, then
the client-side ITR gives the server-side ETR responsibility for
bidirectional RLOC reachability and preferability. Server-side
ETR gleaning of the client-side ITR RLOC is done by caching the
inner-header source EID and the outer-header source RLOC of
received packets. The client-side ITR controls how traffic is
returned and can, as an alternative, use an outer-header source
RLOC, which then can be added to the list the server-side ETR uses
to return traffic. Since no Priority or Weights are provided
using this method, the server-side ETR MUST assume that each
client-side ITR RLOC uses the same best Priority with a Weight
of zero. In addition, since EID-Prefix encoding cannot be conveyed
in data packets, the EID-to-RLOC Map-Cache on Tunnel Routers can grow
very large. Gleaning has several important considerations.
A "gleaned" Map-Cache entry is only stored and used for a RECOMMENDED period of 3 seconds,
pending verification. Verification MUST be performed by
sending a Map-Request to the source EID (the inner-header IP source
address) of the received encapsulated packet. A reply to this
"verifying Map-Request" is used to fully populate the Map-Cache entry
for the "gleaned" EID and is stored and used for the time indicated
in the 'Time to Live' field of a received Map-Reply. When a verified Map-Cache entry is stored, data gleaning no longer occurs for subsequent
packets that have a source EID that matches the EID-Prefix of the
verified entry. This "gleaning" mechanism MUST NOT be used over
the public Internet and SHOULD only be used in trusted and closed
deployments. Refer to for security issues regarding this
mechanism.
RLOCs that appear in EID-to-RLOC Map-Reply messages are
assumed to be reachable when the R-bit for the Locator record is set
to 1. When the R-bit is set to 0, an ITR or PITR MUST NOT
encapsulate to the RLOC. Neither the information contained in
a Map-Reply nor that stored in the mapping database system
provides reachability information for RLOCs. Note that
reachability is not part of the Mapping System and is
determined using one or more of the RLOC
reachability algorithms described in the next section.Routing Locator ReachabilitySeveral data plane mechanisms for determining RLOC
reachability are currently defined. Please note that
additional reachability mechanisms based on the control plane are
defined in .
An ETR MAY examine the Locator-Status-Bits in the LISP
header of an encapsulated data packet received from an
ITR. If the ETR is also acting as an ITR and has
traffic to return to the original ITR site, it can use
this status information to help select an RLOC.
When an ETR receives an encapsulated packet from an ITR,
the source RLOC from the outer header of the packet is likely
to be reachable. Please note that in some scenarios the
RLOC from the outer header can be a spoofable field.
An ITR/ETR pair can use the Echo-Noncing Locator
reachability algorithms described in this section.
When determining Locator up/down reachability by
examining the Locator-Status-Bits from the LISP-encapsulated
data packet, an ETR will receive an up-to-date status from an
encapsulating ITR about reachability for all ETRs at the
site. CE-based ITRs at the source site can determine
reachability relative to each other using the site IGP as
follows:
Under normal circumstances, each ITR will advertise
a default route into the site IGP.
If an ITR fails or if the upstream link to its Provider Edge
fails, its default route will either time out or be
withdrawn.
Each ITR can thus observe the presence or lack of a
default route originated by the others to determine the
Locator-Status-Bits it sets for them.When ITRs at the site are not deployed in CE routers, the IGP
can still be used to determine the reachability of Locators,
provided they are injected into the IGP. This is
typically done when a /32 address is configured on a loopback
interface. RLOCs listed in a Map-Reply are numbered with ordinals
0 to n-1. The Locator-Status-Bits in a LISP-encapsulated
packet are numbered from 0 to n-1 starting with the least
significant bit. For example, if an RLOC listed in the 3rd
position of the Map-Reply goes down (ordinal value 2),
then all ITRs at the site will clear the 3rd least
significant bit (xxxx x0xx) of the 'Locator-Status-Bits'
field for the packets they encapsulate.When an xTR decides to use Locator-Status-Bits
to affect reachability information, it acts as follows:
ETRs decapsulating a packet will check for any change in
the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the
ETR, if also acting as an ITR, will refrain from encapsulating
packets to an RLOC that is indicated as down. It will only resume
using that RLOC if the corresponding Locator-Status-Bit
returns to a value of 1. Locator-Status-Bits are associated with a Locator-Set
per EID-Prefix. Therefore, when a Locator becomes unreachable, the
Locator-Status-Bit that corresponds to that Locator's position in the
list returned by the last Map-Reply will be set to zero for that
particular EID-Prefix.
Locator-Status-Bits MUST NOT be used
over the public Internet and SHOULD only be used in trusted
and closed deployments. In addition, Locator-Status-Bits
SHOULD be coupled with Map-Versioning
to prevent race conditions where Locator-Status-Bits are interpreted as
referring to different RLOCs than intended. Refer to
for security issues regarding this mechanism.If an ITR encapsulates a packet to an ETR and the packet is
received and decapsulated by the ETR, it is implied, but not
confirmed by the ITR, that the ETR's RLOC is reachable. In
most cases, the ETR can also reach the ITR but cannot assume
this to be true, due to the possibility of path asymmetry. In
the presence of unidirectional traffic flow from an ITR to an
ETR, the ITR SHOULD NOT use the lack of return traffic as an
indication that the ETR is unreachable. Instead, it MUST use
an alternate mechanism to determine reachability.The security considerations of
related to data plane reachability apply to the data plane
RLOC reachability mechanisms described in this section.Echo-Nonce AlgorithmWhen data flows bidirectionally between Locators from
different sites, a data plane mechanism called "nonce
echoing" can be used to determine reachability between an ITR
and ETR. When an ITR wants to solicit a nonce echo, it sets
the N- and E-bits and places a 24-bit nonce in the LISP header of the next
encapsulated data packet.When this packet is received by the ETR, the encapsulated
packet is forwarded as normal. When the ETR is an xTR
(co-located as an ITR), it then sends a data packet to the
ITR (when it is an xTR co-located as an ETR) and includes the
nonce received earlier with the N-bit set and E-bit
cleared. The ITR sees this "echoed nonce" and knows that the
path to and from the ETR is up.The ITR will set the E-bit and N-bit for every packet it
sends while in the Echo-Nonce-request state. The time the
ITR waits to process the echoed nonce before it determines that
the path is unreachable is variable and is a choice left for
the implementation.If the ITR is receiving packets from the ETR but does not
see the nonce echoed while being in the Echo-Nonce-request
state, then the path to the ETR is unreachable. This decision
MAY be overridden by other Locator reachability
algorithms. Once the ITR determines that the path to the ETR
is down, it can switch to another Locator for that
EID-Prefix.Note that "ITR" and "ETR" are relative terms here. Both
devices MUST be implementing both ITR and ETR functionality
for the Echo-Nonce mechanism to operate.The ITR and ETR MAY both go into the Echo-Nonce-request
state at the same time. The number of packets sent or the
time during which Echo-Nonce request packets are sent is an
implementation-specific setting. In this case, an xTR
receiving the Echo-Nonce request packets will suspend
the Echo-Nonce state and set up an 'Echo-Nonce-request-state' timer.
After the 'Echo-Nonce-request-state' timer expires, it will resume
the Echo-Nonce state.This mechanism does not completely solve the forward path
reachability problem, as traffic may be unidirectional. That
is, the ETR receiving traffic at a site MAY not be the same
device as an ITR that transmits traffic from that site, or
the site-to-site traffic is unidirectional so there is no ITR
returning traffic.The Echo-Nonce algorithm is bilateral. That is, if one
side sets the E-bit and the other side is not enabled for
Echo-Noncing, then the echoing of the nonce does not occur
and the requesting side may erroneously consider the Locator
unreachable. An ITR SHOULD set the E-bit in an
encapsulated data packet when it knows the ETR is enabled for
Echo-Noncing. This is conveyed by the E-bit in the
Map-Reply message.Many implementations default to not advertising that they are
Echo-Nonce capable in Map-Reply messages, and so RLOC-Probing tends
to be used for RLOC reachability.The Echo-Nonce mechanism MUST NOT be used
over the public Internet and MUST only be used in trusted
and closed deployments. Refer to for
security issues regarding this mechanism.EID Reachability within a LISP SiteA site MAY be multihomed using two or more ETRs. The hosts
and infrastructure within a site will be addressed using one
or more EID-Prefixes that are mapped to the RLOCs of the
relevant ETRs in the Mapping System. One possible failure
mode is for an ETR to lose reachability to one or more of the
EID-Prefixes within its own site. When this occurs when the
ETR sends Map-Replies, it can clear the R-bit associated with
its own Locator. And when the ETR is also an ITR, it can clear
its Locator-Status-Bit in the encapsulation data header.It is recognized that there are no simple solutions to the
site partitioning problem because it is hard to know which
part of the EID-Prefix range is partitioned and which Locators
can reach any sub-ranges of the EID-Prefixes. Note that this
is not a new problem introduced by the LISP architecture. At the time of
this writing, this problem exists when a multihomed site uses BGP to
advertise its reachability upstream.Routing Locator HashingWhen an ETR provides an EID-to-RLOC mapping in a
Map-Reply message that is stored in the Map-Cache of a
requesting ITR, the Locator-Set for the EID-Prefix MAY
contain different Priority and Weight values for each
Routing Locator Address. When more than one best Priority Locator
exists, the ITR can decide how to load-share traffic against
the corresponding Locators.The following hash algorithm MAY be used by an ITR to
select a Locator for a packet destined to an EID for the
EID-to-RLOC mapping:
Either a source and destination address hash or the
commonly used 5-tuple hash can be used. The commonly used
5-tuple hash includes the source and destination
addresses; source and destination TCP, UDP, or Stream
Control Transmission Protocol (SCTP) port numbers; and the
IP protocol number field or IPv6 next-protocol fields of a
packet that a host originates from within a LISP
site. When a packet is not a TCP, UDP, or SCTP packet, the
source and destination addresses only from the header are
used to compute the hash.
Take the hash value and divide it by the number of
Locators stored in the Locator-Set for the EID-to-RLOC
mapping.
The remainder will yield a value of 0 to "number of
Locators minus 1". Use the remainder to select the Locator
in the Locator-Set.
The specific hash algorithm the ITR uses for load-sharing
is out of scope for this document and does not prevent
interoperability.The source port SHOULD be the same for all packets belonging to the
same flow. Also note that when a packet is LISP encapsulated, the source
port number in the outer UDP header needs to be set. Selecting
a hashed value allows core routers that are attached to Link
Aggregation Groups (LAGs) to load-split the encapsulated
packets across member links of such LAGs. Otherwise, core
routers would see a single flow, since packets have a source
address of the ITR, for packets that are originated by
different EIDs at the source site. A suggested setting for the
source port number computed by an ITR is a 5-tuple hash
function on the inner header, as described above. The source
port SHOULD be the same for all packets belonging to the same
flow.Many core router implementations use a 5-tuple hash to decide
how to balance packet load across members of a LAG. The 5-tuple
hash includes the source and destination addresses of the packet
and the source and destination ports when the protocol number in
the packet is TCP or UDP. For this reason, UDP encoding is
used for LISP encapsulation. In this scenario, when the outer header is IPv6, the flow label MAY also be
set following the procedures specified in . When the inner header
is IPv6 and the flow label is not zero, it MAY be used to compute the hash.Changing the Contents of EID-to-RLOC MappingsSince the LISP architecture uses a caching scheme to
retrieve and store EID-to-RLOC mappings, the only way an ITR
can get a more up-to-date mapping is to re-request the
mapping. However, the ITRs do not know when the mappings
change, and the ETRs do not keep track of which ITRs
requested their mappings. For scalability reasons, it is
desirable to maintain this approach, but implementors need to provide a
way for ETRs to change their mappings and inform the sites
that are currently communicating with the ETR site using
such mappings.This section defines two data plane mechanism for updating
EID-to-RLOC mappings. Additionally, the Solicit-Map-Request
(SMR) control plane updating mechanism is specified in .Locator-Status-BitsLocator-Status-Bits (LSBs) can also be used to keep track of the
Locator status (up or down) when EID-to-RLOC mappings are changing. When LSBs are used in a LISP deployment, all LISP Tunnel Routers MUST implement both ITR and ETR capabilities (therefore, all Tunnel Routers are effectively xTRs). In this section, the term "source xTR" is used to refer to the xTR setting the LSB and "destination xTR" is used to refer to the xTR receiving the LSB. The procedure is as follows:
When a Locator record is added or removed from the Locator-Set, the source xTR
will signal this by sending an SMR control plane message to the destination xTR. At this point, the source xTR MUST NOT use the LSB field, when the L-bit is 0,
since the destination xTR site has outdated information.
The source xTR will set up a 'use-LSB' timer.
As defined in ,
upon reception of the SMR message, the destination xTR will retrieve the updated
EID-to-RLOC mappings by sending a Map-Request.
When the 'use-LSB' timer expires, the source xTR can use the LSB again with the destination xTR to signal the Locator status (up or down).
The specific value for the 'use-LSB' timer depends on the LISP deployment; the 'use-LSB' timer needs to be large enough
for the destination xTR to retrieve the updated EID-to-RLOC mappings. A RECOMMENDED value for the 'use-LSB' timer is 5 minutes.
Database Map-VersioningWhen there is unidirectional packet flow between an ITR and
ETR, and the EID-to-RLOC mappings change on the ETR, it needs to
inform the ITR so encapsulation to a removed Locator can stop
and can instead be started to a new Locator in the
Locator-Set.An ETR can send Map-Reply messages carrying a Map-Version Number in
an EID-Record. This is known as the Destination Map-Version Number.
ITRs include the Destination Map-Version Number in packets they
encapsulate to the site.An ITR, when it encapsulates packets to ETRs, can convey its own Map-
Version Number. This is known as the Source Map-Version Number.When presented in EID-Records of Map-Register messages , a Map-Version
Number is a good way for the Map-Server to assure that all ETRs for a
site registering to it are synchronized according to the Map-Version
Number.See for a more
detailed analysis and description of Database
Map-Versioning.Multicast ConsiderationsA multicast group address, as defined in the original Internet
architecture, is an identifier of a grouping of topologically
independent receiver host locations. The address encoding itself
does not determine the location of the receiver(s). The multicast
routing protocol and the network-based state the protocol creates
determine where the receivers are located.In the context of LISP, a multicast group address is both an
EID and an RLOC. Therefore, no specific semantic or
action needs to be taken for a destination address, as it would
appear in an IP header. Therefore, a group address that
appears in an inner IP header built by a source host will be
used as the destination EID. The outer IP header (the
destination RLOC address), prepended by a LISP
router, can use the same group address as the destination
RLOC, use a multicast or unicast RLOC
obtained from a Mapping System lookup, or use other means to
determine the group address mapping.With respect to the source RLOC address, the ITR
prepends its own IP address as the source address of the outer
IP header, just like it would if the destination EID was a
unicast address. This source RLOC address, like any
other RLOC address, MUST be routable on the underlay.There are two approaches for LISP-Multicast : one that uses
native multicast routing in the underlay with no support from
the Mapping System and another that uses only unicast routing
in the underlay with support from the Mapping System. See and , respectively,
for details. Details for LISP-Multicast and interworking with
non-LISP sites are described in and
, respectively.Router Performance ConsiderationsLISP is designed to be very "hardware based and forwarding
friendly". A few implementation techniques can be used to
incrementally implement LISP:
When a tunnel-encapsulated packet is received by an
ETR, the outer destination address may not be the address
of the router. This makes it challenging for the control
plane to get packets from the hardware. This may be
mitigated by creating special Forwarding Information Base
(FIB) entries for the EID-Prefixes of EIDs served by the
ETR (those for which the router provides an RLOC
translation). These FIB entries are marked with a flag
indicating that control plane processing SHOULD be
performed. The forwarding logic of testing for particular
IP protocol number values is not necessary. There are a
few proven cases where no changes to existing deployed
hardware were needed to support the LISP data plane.
On an ITR, prepending a new IP header consists of adding
more octets to a Message Authentication Code (MAC) rewrite string and prepending the
string as part of the outgoing encapsulation
procedure. Routers that support Generic Routing Encapsulation
(GRE) tunneling or 6to4 tunneling
may already support this
action.
A packet's source address or the interface on which the
packet was received can be used to select
Virtual Routing and Forwarding (VRF). The VRF system's routing table
can be used to find EID-to-RLOC mappings.
For performance issues related to Map-Cache management, see
.Security ConsiderationsIn what follows, we highlight security
considerations that apply when LISP is deployed in environments such
as those specified in .The optional gleaning mechanism is offered to directly obtain
a mapping from the LISP-encapsulated packets. Specifically, an xTR
can learn the EID-to-RLOC mapping by inspecting the source RLOC and
source EID of an encapsulated packet and insert this new mapping
into its Map-Cache. An off-path attacker can spoof the source EID
address to divert the traffic sent to the victim's spoofed EID. If
the attacker spoofs the source RLOC, it can mount a DoS attack by
redirecting traffic to the spoofed victim's RLOC, potentially
overloading it.The LISP data plane defines several mechanisms to monitor RLOC
data plane reachability; in this context, Locator-Status-Bits,
nonce-present bits, and Echo-Nonce bits of the LISP encapsulation header
can be manipulated by an attacker to mount a DoS attack. An off-path
attacker able to spoof the RLOC and/or nonce of a victim's xTR can
manipulate such mechanisms to declare false information about the
RLOC's reachability status.An example of such attacks is when an off-path attacker can exploit the
Echo-Nonce mechanism by sending data packets to an ITR with a random
nonce from an ETR's spoofed RLOC. Note that the attacker only has a small window
of time within which to guess a valid nonce that the ITR is requesting to be echoed. The goal is to convince the ITR that the ETR's RLOC is
reachable even when it may not be reachable. If the attack is
successful, the ITR believes the wrong reachability status of the
ETR's RLOC until RLOC-Probing detects the correct status. This time
frame is on the order of tens of seconds. This specific attack can
be mitigated by preventing RLOC spoofing in the network by deploying
Unicast Reverse Path Forwarding (uRPF) per BCP 84. In order to exploit
this vulnerability, the off-path attacker must also send Echo-Nonce
packets at a high rate. If the nonces have never been requested by the
ITR, it can protect itself from erroneous reachability attacks.A LISP-specific uRPF check is also possible. When decapsulating,
an ETR can check that the source EID and RLOC are valid EID-to-RLOC
mappings by checking the Mapping System.Map-Versioning is a data plane mechanism used to signal to a peering
xTR that a local EID-to-RLOC mapping has been updated so that the
peering xTR uses a LISP control plane signaling message to retrieve a
fresh mapping. This can be used by an attacker to forge the
'Map-Version' field of a LISP-encapsulated header and force an
excessive amount of signaling between xTRs that may overload them.
Further security considerations on Map-Versioning can be found in
.Locator-Status-Bits, the Echo-Nonce mechanism, and Map-Versioning MUST NOT be used
over the public Internet and SHOULD only be used in trusted
and closed deployments. In addition, Locator-Status-Bits
SHOULD be coupled with Map-Versioning to prevent race conditions
where Locator-Status-Bits are interpreted as referring to different RLOCs than intended.LISP implementations and deployments that permit outer header fragments
of IPv6 LISP-encapsulated packets as a means of dealing with MTU issues
should also use implementation techniques in ETRs to prevent this
from being a DoS attack vector. Limits on the number of fragments
awaiting reassembly at an ETR, RTR, or PETR, and the rate of admitting
such fragments, may be used.Network Management ConsiderationsConsiderations for network management tools exist so the LISP
protocol suite can be operationally managed. These mechanisms can
be found in and .Changes since RFC 6830For implementation considerations, the following changes have been made
to this document since was published:
It is no longer mandated that a maximum number of 2 LISP
headers be prepended to a packet. If there is an application need
for more than 2 LISP headers, an implementation can support
more. However, it is RECOMMENDED that a maximum of 2 LISP
headers can be prepended to a packet.
The 3 reserved flag bits in the LISP header have been allocated
for . The low-order 2 bits of the 3-bit
field (now named the KK-bits) are used as a key identifier. The 1
remaining bit is still documented as reserved and unassigned.
Data plane gleaning for creating Map-Cache entries has been
made optional. Any ITR implementations that depend on or assume that the
remote ETR is gleaning should not do so. This does not create any
interoperability problems, since the control plane Map-Cache
population procedures are unilateral and are the typical method
for populating the Map-Cache.
Most of the changes to this document, which reduce its
length, are due to moving the LISP control plane messaging and
procedures to .
IANA ConsiderationsThis section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to this
data plane LISP specification, in accordance with BCP 26.LISP UDP Port NumbersIANA has allocated UDP port number 4341 for the
LISP data plane. IANA has updated the description for UDP port
4341 as follows:
Service Name
Port Number
Transport Protocol
Description
Reference
lisp-data
4341
udp
LISP Data Packets
RFC 9300
ReferencesNormative ReferencesUser Datagram ProtocolInternet ProtocolKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 HeadersThis document defines the IP header field, called the DS (for differentiated services) field. [STANDARDS-TRACK]Differentiated Services and TunnelsThis document considers the interaction of Differentiated Services (diffserv) with IP tunnels of various forms. This memo provides information for the Internet community.Tunnelling of Explicit Congestion NotificationThis document redefines how the explicit congestion notification (ECN) field of the IP header should be constructed on entry to and exit from any IP-in-IP tunnel. On encapsulation, it updates RFC 3168 to bring all IP-in-IP tunnels (v4 or v6) into line with RFC 4301 IPsec ECN processing. On decapsulation, it updates both RFC 3168 and RFC 4301 to add new behaviours for previously unused combinations of inner and outer headers. The new rules ensure the ECN field is correctly propagated across a tunnel whether it is used to signal one or two severity levels of congestion; whereas before, only one severity level was supported. Tunnel endpoints can be updated in any order without affecting pre-existing uses of the ECN field, thus ensuring backward compatibility. Nonetheless, operators wanting to support two severity levels (e.g., for pre-congestion notification -- PCN) can require compliance with this new specification. A thorough analysis of the reasoning for these changes and the implications is included. In the unlikely event that the new rules do not meet a specific need, RFC 4774 gives guidance on designing alternate ECN semantics, and this document extends that to include tunnelling issues. [STANDARDS-TRACK]Using the IPv6 Flow Label for Equal Cost Multipath Routing and Link Aggregation in TunnelsThe IPv6 flow label has certain restrictions on its use. This document describes how those restrictions apply when using the flow label for load balancing by equal cost multipath routing and for link aggregation, particularly for IP-in-IPv6 tunneled traffic. [STANDARDS-TRACK]The Locator/ID Separation Protocol (LISP)This document describes a network-layer-based protocol that enables separation of IP addresses into two new numbering spaces: Endpoint Identifiers (EIDs) and Routing Locators (RLOCs). No changes are required to either host protocol stacks or to the "core" of the Internet infrastructure. The Locator/ID Separation Protocol (LISP) can be incrementally deployed, without a "flag day", and offers Traffic Engineering, multihoming, and mobility benefits to early adopters, even when there are relatively few LISP-capable sites.Design and development of LISP was largely motivated by the problem statement produced by the October 2006 IAB Routing and Addressing Workshop. This document defines an Experimental Protocol for the Internet community.The Locator/ID Separation Protocol (LISP) for Multicast EnvironmentsThis document describes how inter-domain multicast routing will function in an environment where Locator/ID Separation is deployed using the Locator/ID Separation Protocol (LISP) architecture. This document defines an Experimental Protocol for the Internet community.Guidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Internet Protocol, Version 6 (IPv6) SpecificationThis document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.Signal-Free Locator/ID Separation Protocol (LISP) MulticastWhen multicast sources and receivers are active at Locator/ID Separation Protocol (LISP) sites, the core network is required to use native multicast so packets can be delivered from sources to group members. When multicast is not available to connect the multicast sites together, a signal-free mechanism can be used to allow traffic to flow between sites. The mechanism described in this document uses unicast replication and encapsulation over the core network for the data plane and uses the LISP mapping database system so encapsulators at the source LISP multicast site can find decapsulators at the receiver LISP multicast sites.Enhanced Feasible-Path Unicast Reverse Path ForwardingThis document identifies a need for and proposes improvement of the unicast Reverse Path Forwarding (uRPF) techniques (see RFC 3704) for detection and mitigation of source address spoofing (see BCP 38). Strict uRPF is inflexible about directionality, the loose uRPF is oblivious to directionality, and the current feasible-path uRPF attempts to strike a balance between the two (see RFC 3704). However, as shown in this document, the existing feasible-path uRPF still has shortcomings. This document describes enhanced feasible-path uRPF (EFP-uRPF) techniques that are more flexible (in a meaningful way) about directionality than the feasible-path uRPF (RFC 3704). The proposed EFP-uRPF methods aim to significantly reduce false positives regarding invalid detection in source address validation (SAV). Hence, they can potentially alleviate ISPs' concerns about the possibility of disrupting service for their customers and encourage greater deployment of uRPF techniques. This document updates RFC 3704.Locator/ID Separation Protocol (LISP) Control PlaneLocator/ID Separation Protocol (LISP) Map-VersioningInformative ReferencesAddress Family NumbersIANAEndpoints and Endpoint Names: A Proposed Enhancement to the Internet ArchitectureLISP Virtual Private Networks (VPNs)Google LLClispers.net This document describes the use of the Locator/ID Separation Protocol
(LISP) to create Virtual Private Networks (VPNs). LISP is used to
provide segmentation in both the LISP data plane and control plane.
These VPNs can be created over the top of the Internet or over
private transport networks, and can be implemented by Enterprises or
Service Providers. The goal of these VPNs is to leverage the
characteristics of LISP - routing scalability, simply expressed
Ingress site TE Policy, IP Address Family traversal, and mobility, in
ways that provide value to network operators.
Work in ProgressDomain names - concepts and facilitiesThis RFC is the revised basic definition of The Domain Name System. It obsoletes RFC-882. This memo describes the domain style names and their used for host address look up and electronic mail forwarding. It discusses the clients and servers in the domain name system and the protocol used between them.Path MTU discoveryThis memo describes a technique for dynamically discovering the maximum transmission unit (MTU) of an arbitrary internet path. It specifies a small change to the way routers generate one type of ICMP message. For a path that passes through a router that has not been so changed, this technique might not discover the correct Path MTU, but it will always choose a Path MTU as accurate as, and in many cases more accurate than, the Path MTU that would be chosen by current practice. [STANDARDS-TRACK]RIP Version 2This document specifies an extension of the Routing Information Protocol (RIP) to expand the amount of useful information carried in RIP messages and to add a measure of security. [STANDARDS-TRACK]Definitions of Managed Objects for the NBMA Next Hop Resolution Protocol (NHRP)This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. [STANDARDS-TRACK]Generic Routing Encapsulation (GRE)This document specifies a protocol for encapsulation of an arbitrary network layer protocol over another arbitrary network layer protocol. [STANDARDS-TRACK]Connection of IPv6 Domains via IPv4 CloudsThis memo specifies an optional interim mechanism for IPv6 sites to communicate with each other over the IPv4 network without explicit tunnel setup, and for them to communicate with native IPv6 domains via relay routers. [STANDARDS-TRACK]SIP: Session Initiation ProtocolThis document describes Session Initiation Protocol (SIP), an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences. [STANDARDS-TRACK]Randomness Requirements for SecuritySecurity systems are built on strong cryptographic algorithms that foil pattern analysis attempts. However, the security of these systems is dependent on generating secret quantities for passwords, cryptographic keys, and similar quantities. The use of pseudo-random processes to generate secret quantities can result in pseudo-security. A sophisticated attacker may find it easier to reproduce the environment that produced the secret quantities and to search the resulting small set of possibilities than to locate the quantities in the whole of the potential number space.Choosing random quantities to foil a resourceful and motivated adversary is surprisingly difficult. This document points out many pitfalls in using poor entropy sources or traditional pseudo-random number generation techniques for generating such quantities. It recommends the use of truly random hardware techniques and shows that the existing hardware on many systems can be used for this purpose. It provides suggestions to ameliorate the problem when a hardware solution is not available, and it gives examples of how large such quantities need to be for some applications. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.MTU and Fragmentation Issues with In-the-Network TunnelingTunneling techniques such as IP-in-IP when deployed in the middle of the network, typically between routers, have certain issues regarding how large packets can be handled: whether such packets would be fragmented and reassembled (and how), whether Path MTU Discovery would be used, or how this scenario could be operationally avoided. This memo justifies why this is a common, non-trivial problem, and goes on to describe the different solutions and their characteristics at some length. This memo provides information for the Internet community.Multiprotocol Extensions for BGP-4This document defines extensions to BGP-4 to enable it to carry routing information for multiple Network Layer protocols (e.g., IPv6, IPX, L3VPN, etc.). The extensions are backward compatible - a router that supports the extensions can interoperate with a router that doesn't support the extensions. [STANDARDS-TRACK]Packetization Layer Path MTU DiscoveryThis document describes a robust method for Path MTU Discovery (PMTUD) that relies on TCP or some other Packetization Layer to probe an Internet path with progressively larger packets. This method is described as an extension to RFC 1191 and RFC 1981, which specify ICMP-based Path MTU Discovery for IP versions 4 and 6, respectively. [STANDARDS-TRACK]Report from the IAB Workshop on Routing and AddressingThis document reports the outcome of the Routing and Addressing Workshop that was held by the Internet Architecture Board (IAB) on October 18-19, 2006, in Amsterdam, Netherlands. The primary goal of the workshop was to develop a shared understanding of the problems that the large backbone operators are facing regarding the scalability of today's Internet routing system. The key workshop findings include an analysis of the major factors that are driving routing table growth, constraints in router technology, and the limitations of today's Internet addressing architecture. It is hoped that these findings will serve as input to the IETF community and help identify next steps towards effective solutions.Note that this document is a report on the proceedings of the workshop. The views and positions documented in this report are those of the workshop participants and not of the IAB. Furthermore, note that work on issues related to this workshop report is continuing, and this document does not intend to reflect the increased understanding of issues nor to discuss the range of potential solutions that may be the outcome of this ongoing work. This memo provides information for the Internet community.Interworking between Locator/ID Separation Protocol (LISP) and Non-LISP SitesThis document describes techniques for allowing sites running the Locator/ID Separation Protocol (LISP) to interoperate with Internet sites that may be using either IPv4, IPv6, or both but that are not running LISP. A fundamental property of LISP-speaking sites is that they use Endpoint Identifiers (EIDs), rather than traditional IP addresses, in the source and destination fields of all traffic they emit or receive. While EIDs are syntactically identical to IPv4 or IPv6 addresses, normally routes to them are not carried in the global routing system, so an interoperability mechanism is needed for non- LISP-speaking sites to exchange traffic with LISP-speaking sites. This document introduces three such mechanisms. The first uses a new network element, the LISP Proxy Ingress Tunnel Router (Proxy-ITR), to act as an intermediate LISP Ingress Tunnel Router (ITR) for non-LISP- speaking hosts. Second, this document adds Network Address Translation (NAT) functionality to LISP ITRs and LISP Egress Tunnel Routers (ETRs) to substitute routable IP addresses for non-routable EIDs. Finally, this document introduces the Proxy Egress Tunnel Router (Proxy-ETR) to handle cases where a LISP ITR cannot send packets to non-LISP sites without encapsulation. This document defines an Experimental Protocol for the Internet community.The Locator/ID Separation Protocol Internet Groper (LIG)A simple tool called the Locator/ID Separation Protocol (LISP) Internet Groper or 'lig' can be used to query the LISP mapping database. This document describes how it works. This document is not an Internet Standards Track specification; it is published for informational purposes.IPv6 and UDP Checksums for Tunneled PacketsThis document updates the IPv6 specification (RFC 2460) to improve performance when a tunnel protocol uses UDP with IPv6 to tunnel packets. The performance improvement is obtained by relaxing the IPv6 UDP checksum requirement for tunnel protocols whose header information is protected on the "inner" packet being carried. Relaxing this requirement removes the overhead associated with the computation of UDP checksums on IPv6 packets that carry the tunnel protocol packets. This specification describes how the IPv6 UDP checksum requirement can be relaxed when the encapsulated packet itself contains a checksum. It also describes the limitations and risks of this approach and discusses the restrictions on the use of this method.Applicability Statement for the Use of IPv6 UDP Datagrams with Zero ChecksumsThis document provides an applicability statement for the use of UDP transport checksums with IPv6. It defines recommendations and requirements for the use of IPv6 UDP datagrams with a zero UDP checksum. It describes the issues and design principles that need to be considered when UDP is used with IPv6 to support tunnel encapsulations, and it examines the role of the IPv6 UDP transport checksum. The document also identifies issues and constraints for deployment on network paths that include middleboxes. An appendix presents a summary of the trade-offs that were considered in evaluating the safety of the update to RFC 2460 that changes the use of the UDP checksum with IPv6.Locator/ID Separation Protocol (LISP) MIBThis document defines the MIB module that contains managed objects to support the monitoring devices of the Locator/ID Separation Protocol (LISP). These objects provide information useful for monitoring LISP devices, including determining basic LISP configuration information, LISP functional status, and operational counters and other statistics.Locator/Identifier Separation Protocol (LISP) Network Element Deployment ConsiderationsThis document is a snapshot of different Locator/Identifier Separation Protocol (LISP) deployment scenarios. It discusses the placement of new network elements introduced by the protocol, representing the thinking of the LISP working group as of Summer 2013. LISP deployment scenarios may have evolved since then. This memo represents one stable point in that evolution of understanding.LISP Canonical Address Format (LCAF)This document defines a canonical address format encoding used in Locator/ID Separation Protocol (LISP) control messages and in the encoding of lookup keys for the LISP Mapping Database System.Locator/ID Separation Protocol (LISP) Data-Plane ConfidentialityThis document describes a mechanism for encrypting traffic encapsulated using the Locator/ID Separation Protocol (LISP). The design describes how key exchange is achieved using existing LISP control-plane mechanisms as well as how to secure the LISP data plane from third-party surveillance attacks.UDP Usage GuidelinesThe User Datagram Protocol (UDP) provides a minimal message-passing transport that has no inherent congestion control mechanisms. This document provides guidelines on the use of UDP for the designers of applications, tunnels, and other protocols that use UDP. Congestion control guidelines are a primary focus, but the document also provides guidance on other topics, including message sizes, reliability, checksums, middlebox traversal, the use of Explicit Congestion Notification (ECN), Differentiated Services Code Points (DSCPs), and ports.Because congestion control is critical to the stable operation of the Internet, applications and other protocols that choose to use UDP as an Internet transport must employ mechanisms to prevent congestion collapse and to establish some degree of fairness with concurrent traffic. They may also need to implement additional mechanisms, depending on how they use UDP.Some guidance is also applicable to the design of other protocols (e.g., protocols layered directly on IP or via IP-based tunnels), especially when these protocols do not themselves provide congestion control.This document obsoletes RFC 5405 and adds guidelines for multicast UDP usage.Path MTU Discovery for IP version 6This document describes Path MTU Discovery (PMTUD) for IP version 6. It is largely derived from RFC 1191, which describes Path MTU Discovery for IP version 4. It obsoletes RFC 1981.Packetization Layer Path MTU Discovery for Datagram TransportsThis document specifies Datagram Packetization Layer Path MTU Discovery (DPLPMTUD). This is a robust method for Path MTU Discovery (PMTUD) for datagram Packetization Layers (PLs). It allows a PL, or a datagram application that uses a PL, to discover whether a network path can support the current size of datagram. This can be used to detect and reduce the message size when a sender encounters a packet black hole. It can also probe a network path to discover whether the maximum packet size can be increased. This provides functionality for datagram transports that is equivalent to the PLPMTUD specification for TCP, specified in RFC 4821, which it updates. It also updates the UDP Usage Guidelines to refer to this method for use with UDP datagrams and updates SCTP.The document provides implementation notes for incorporating Datagram PMTUD into IETF datagram transports or applications that use datagram transports.This specification updates RFC 4960, RFC 4821, RFC 6951, RFC 8085, and RFC 8261.An Architectural Introduction to the Locator/ID Separation Protocol (LISP)AcknowledgmentsAn initial thank you goes to for planting the seeds for
the initial ideas for LISP. His consultation continues to provide
value to the LISP authors.A special and appreciative thank you goes to for
providing architectural impetus over the past decades on separation
of location and identity, as well as detailed reviews of the LISP
architecture and documents, coupled with enthusiasm for making LISP
a practical and incremental transition for the Internet.The original authors would like to gratefully acknowledge many people who
have contributed discussions and ideas to the making of this
proposal. They include , , ,
, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
, , , ,
, , , ,
, , , ,
, , , , , , , , ,
, , , , , , , , ,
, , , , and .This work originated in the Routing Research Group (RRG) of the
IRTF. An individual submission was converted into the IETF LISP
Working Group document that became this RFC.The LISP Working Group would like to give a special thanks to
, the Internet Area AD at the time that the set of LISP
documents was being prepared for IESG Last Call, for his
meticulous reviews and detailed commentaries on the 7 Working Group
Last Call documents progressing toward Standards Track RFCs.The current authors would like to give a sincere thank you to the
people who helped put LISP on the Standards Track in the IETF. They
include , , , ,
, , , , ,
, , , , , , , , , , , ,
, , and . The contributions
they offered greatly added to the security, scale, and robustness of
the LISP architecture and protocols.Authors' Addresseslispers.netSan JoseCAUnited States of Americafarinacci@gmail.comvaf.net Internet Consultingvince.fuller@gmail.com1-4-5.netdmm@1-4-5.netCisco SystemsSan JoseCAUnited States of Americadarlewis@cisco.comUniversitat Politecnica de Catalunyac/ Jordi Girona s/nBarcelona08034Spainacabello@ac.upc.edu