Subject: PID --- a new option for Stateless Address Auto-Configuration

From: "CTO WEN Haibo" <[email-masked]>
Date: Tue, 6 Jun 2006 13:57:36 +0800

Dear all,

With the more and more mature of IPv6 technology, IPv6 will sure be
deployed in access network. Considering most part of existing network
devices in access networks are layer2 devices, operators would like to
deploy IPv6 services on existing infrastructure as much as possible. 
Less network devices upgrading to layer3 devices are more favorable.

Draft-wen-ipv6-rsra-opt-pid-00.txt is considering help implement IPv6
Stateless Address Auto-Configuration in access network without upgrading
access node and CPE to be layer3 devices. This option doesn't change 
the standard IPv6 mechanism, while it adds more availability to IPv6. 
Because PID option can co-exist with existing options in SAAC.  

FAQ summary is also presented below. Please check it.
Hope everyone could give some comments on this proposal. Thanks in advance.

Best regards,

Haibo

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: Port Identifier option for RS/RA messages in IPv6 access network
	Author(s)	: H. Wen
	Filename	: draft-wen-ipv6-rsra-opt-pid-00.txt
	Pages		: 11
	Date		: 2006-4-4
	
This document makes an extension to stateless address auto-
configuration (SAAC) mechanism by defining Port Identifier option for
RS/RA messages in IPv6 access network. This option can make SAAC 
possible without upgrading access node and CPE to be layer 3 devices.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-wen-ipv6-rsra-opt-pid-00.txt

================= FAQ summary ===================

/1. co-existence of two scenarios

In future IPv6 access network, the following two scenarios will
co-exist as the figure shows.
(1) there is a router in the subscriber network
(2) there is no router in the subscriber network, and only L2 CPE
and L2 AN exist.

+--------+    +---------+ A    B +--+------+    +--------------+
| host1  |----| router1 |--------| L2 AN   |----|  BRAS/router |
+--------+    +---------+        +---+-----+    +--------------+
                                C|   |
                                 |   |
        +--------+       +-------+-+ |
        |  host2 |-------| L2 CPE  | |
        +--------+       +---------+ |
                                    D|
           +--------+       +--------++ 
           |  host3 |-------| L2 CPE  |
           +--------+       +---------+
                            /
                    +------/ 
                    | host |
                    +------+

/2. motivation of this proposal

Nowadays, operators like to run their access networks as simple
as possilbe: access node (i.e., AN) is a layer2 device, no routed
CPE in the subscriber network. Our goal is to implement Stateless
Address Auto-Configuration (SAAC) in access network without 
upgrading existing devices to be layer3 devices, thus we can 
protect existing investment. That is to say, our proposal is used
for the second scenario in the above section (/1.).

/3. The policy for IPv6 prefix allocation

One prefix per subscriber network is deployed. why?
(1) Many devices in the subscriber network (e.g., PCs, TVs, camera,
and electrical applicances) will be connected to the Internet. And
each device will have an IPv6 global address. 
(2) That one prefix is shared by multiple subscriber networks in 
SAAC environment will lead to security issues and also complicated
implementation of access node.
(3) There are so many /64 prefixes, which are adequate for assigning
a prefix to each subscriber network.

/4. directly customer-to-customer communication.

Directly customer-to-customer communication is not allowed in L2
access network by operators. All traffic should firstly go to 
BRAS/router. In L2 access node, user segregation (or subscriber 
network segregation) is done on the AN. The traffic from one 
subscriber network is not allowed to directly enter other subscriber
networks(i.e., layer2 segregation).All the packets should go to the BRAS/
router first, then be routed to the appropriate subnet. Current operator 
has implemented this functionality.

/5. The objective of PID

In L2 access network, the subscriber network is connected to an AN
through subscriber line (i.e., user port of the AN). And the user 
port information is terminated at the AN. That's why DHCP relay 
agent option (option 82) for DHCP in IPv4 and PPPoE+ are defined. 
It's the same for SAAC in access network. When an RS is forwarded 
by AN to BRAS/router. There is no any information that helps BRAS/
router know the exact origination, then BRAS/router don't know 
which prefix should assign to this RS. PID opiton is defined for 
this purpose.

/6. How to use PID option?

Once the L2 AN receives RS message from subscriber network, it 
will insert this PID option with appropriate PID information, 
and forward to BRAS/router. When the BRAS/router receives this RS,
it will advertise a RA message with correct Prefix Information 
option and PID option. The AN removes the PID option from RA and 
forward the RA to the appropriate subscriber network.

/7. what kind of subscriber network will generate RS message to AN?

Only L2 subscriber network will generate RS to AN.
RS/RA messages are used to help hosts/terminals to discovery
prefixes and default router. RS/RA is running between hosts/
terminals and routers.
(1) When there is a router in the subscriber network as gateway 
(as shown in the figure above), obviously the RS generated by host 
(host1) is bounded within the subscriber network.
The interface of the home router (i.e., the interface A of router1)
will not send RS message to access node (i.e., L2 AN), then to the 
BRAS/router. Does the RS/RA message exisit on the point-to-point
link of two routers? If the interface A will  send RS message, 
what's the purpose of this RS message. Route information is 
delivered by routing protocol with link-local addresses. I *don't*
think the interface A of router1will send RS message to BRAS/router.
(2) The RS generated by host 2 will be forwarded by L2 CPE to L2 
AN, then this L2 AN will add PID option.

In a word, the router in the subscriber network will not send RS 
message to the AN, only the L2 subscriber network will send RS 
message to access node.

/8. the impact of the proposal

The softwares of AN and BRAS/router should support PID option. PID
option doesn't have any negative impact on existing IPv6 mechanism.
This proposal aims at implementing SAAC in currently deloyed access
network without requesting the replace of exisint devices. It can
coexist with the scenario that there is a router in the subscriber
network.

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---

From: Lawrence Zou <[email-masked]>
Date: Tue, 06 Jun 2006 19:13:47 +0800

I think the idea in this draft is very good. I only have a question:

Does the BRAS/router still send normal unsolict RA that not along with
the PID option to the subscriber network?

>-----Original Message-----
>From: CTO WEN Haibo [mailto:[email-masked]] 
>Sent: Tuesday, June 06, 2006 1:58 PM
>To: IPv6 WG
>Cc: Jari Arkko; Brian Haberman; Bob Hinden
>Subject: PID --- a new option for Stateless Address Auto-Configuration
>
>
>Dear all,
>
>With the more and more mature of IPv6 technology, IPv6 will 
>sure be deployed in access network. Considering most part of 
>existing network devices in access networks are layer2 
>devices, operators would like to deploy IPv6 services on 
>existing infrastructure as much as possible. 
>Draft-wen-ipv6-rsra-opt-pid-00.txt is considering help 
>implement IPv6 Stateless Address Auto-Configuration in access 
>network without upgrading access node and CPE to be layer3 
>devices. This option doesn't change 
>configuration (SAAC) mechanism by defining Port Identifier 
>option for RS/RA messages in IPv6 access network. This option 
>can make SAAC 
>In future IPv6 access network, the following two scenarios 
>will co-exist as the figure shows.
>(2) there is no router in the subscriber network, and only L2 
>CPE and L2 AN exist.
>
>Nowadays, operators like to run their access networks as 
>simple as possilbe: access node (i.e., AN) is a layer2 device, 
>no routed CPE in the subscriber network. Our goal is to 
>implement Stateless Address Auto-Configuration (SAAC) in 
>access network without 
>protect existing investment. That is to say, our proposal is 
>used for the second scenario in the above section (/1.).
>
>
>(1) Many devices in the subscriber network (e.g., PCs, TVs, 
>camera, and electrical applicances) will be connected to the 
>Internet. And each device will have an IPv6 global address. 
>SAAC environment will lead to security issues and also 
>complicated implementation of access node.
>(3) There are so many /64 prefixes, which are adequate for 
>assigning a prefix to each subscriber network.
>
>
>Directly customer-to-customer communication is not allowed in 
>L2 access network by operators. All traffic should firstly go to 
>subscriber network is not allowed to directly enter other 
>subscriber networks(i.e., layer2 segregation).All the packets 
>should go to the BRAS/ router first, then be routed to the 
>appropriate subnet. Current operator 
>In L2 access network, the subscriber network is connected to 
>an AN through subscriber line (i.e., user port of the AN). And 
>the user 
>by AN to BRAS/router. There is no any information that helps 
>BRAS/ router know the exact origination, then BRAS/router don't know 
>and forward to BRAS/router. When the BRAS/router receives this 
>RS, it will advertise a RA message with correct Prefix Information 
>The interface of the home router (i.e., the interface A of 
>router1) will not send RS message to access node (i.e., L2 
>AN), then to the 
>BRAS/router. Does the RS/RA message exisit on the 
>point-to-point link of two routers? If the interface A will  
>send RS message, 
>delivered by routing protocol with link-local addresses. I 
>*don't* think the interface A of router1will send RS message 
>to BRAS/router.
>The softwares of AN and BRAS/router should support PID option. 
>PID option doesn't have any negative impact on existing IPv6 
>mechanism. This proposal aims at implementing SAAC in 
>currently deloyed access network without requesting the 
>replace of exisint devices. It can coexist with the scenario 
>that there is a router in the subscriber network.
>