Subject: Updated 55th IETF OSPF WG Minutes

From: Acee Lindem <[email-masked]>
Date: Thu, 28 Nov 2002 23:40:31 -0500

I've incorporated comments as well as made some
corrections and edits.
--
Acee
OSPF WG meeting - Thursday 22nd of november - 15:00-17:00
=========================================================

Document status (Acee Lindem and Rohit Dube):
---------------

- RFC 3101 (Not-So-Stubby-Area) currently in final RFC
  editorship
- Traffic engineering extensions to OSPF v2 (a.k.a. OSPF-TE)
  passed the working group last call (completed) - IETF wide
  last call to be issued soon.
- Hitless restart - 04 version to be issued soon. Expect to
  have WG last call on this version.
- Detecting Inactive Neighbors over OSPF Demand Circuits
  (draft-ietf-ospf-dc-05.txt) is pending and is pending
  wg chair comments.
- OSPF Refresh and flooding reduction in stable topologies
  (draft-pillay-esnault-ospf-flooding-04.txt) needs a
  couple of edits but no significant changes.
- Alternative OSPF ABR Implementations (draft-ietf-ospf-abr-
  alt-05.txt) in the comment cycle, it is pretty much done
  and the last call will be issued pretty quickly
- mib-update-05.txt - May want to add the graceful restart
  capabilities

Agenda bashing
--------------

- Acee Lindem: Propose to move hitless restart after Kireeti
  presentation.

- Kireeti Kompella: Agrees

On the Agenda:
-------------

1) Rahul Aggarwal (10 Mins): Extensions to IS-IS and OSPF for
Advertising Optional Router Capabilities
http://www.ietf.org/internet-drafts/draft-raggarwa-igp-cap-01.txt

Summary:
--------

Several changes to this i-d since the last meeting.

1. Review of the motivation and benefits
   - MPLS-TE (and related) capability discovery mechanism
   - Network management and trouble shooting options are
     not extensible thus something generic needed

2. OSPF router information LSA
   - Optional router information LSA of type 4 and opaque ID 0
   - Format of the TLV's in the body of the router info
     information lsa is the same as the TLV format used for
     the TE LSA's
   - Optional TLV must be included as the router capability
     sub-TLV (flags representing the capabilities), sub-TLV
     allows for adding additional information flags in the
     future depending on the needs

3. Router capability bits
   - see i-d

4. Conclusion
   - Application through router local policy
   - Flooding scope dependent on application

Discussion:
-----------

Acee Lindem: LSA option bits limited thus to be extended
             with the sub-TLV

Rohit Dube: No mailing list comments so far. How will
this fit into the charter? Right now there is not a
specific item.

Rahul Aggarwal: Proposal is made here to pass some
information through the use of opaque LSA.

Alex Zinin: Which part of this work is within the charter?
Thus confrontation of this work wrt to the charter needs
to be covered in addition to an IANA consideration section.

Rahul Aggarwal: Agrees

Alex Zinin: FIFO allocation better std based with expert
review before the codepoint allocation by the iana (no
arbitrary stuff) experimental values to be also considered
here.

Tom Petch: Negotiation before exchange these opaque LSAs?
as a first step?

Rahul Aggarwal: Usage is a local matter, and also avoids
the use of negotiation.

Dimitri Papadimitriou: What are the TE mesh groups
mentioned in this i-d? What is behind traffic-engineering?
Are we sure that the underlying concepts are well cooked?
What are the relation with TEWG, the current i-d covers one
of the application of TE, but generic mechanism can also be
considered that overlaps with GMPLS-OSPF.

Rahul Aggarwal: Troubleshooting and specific application
such as path computation server, may need additional work.

Alex Zinin: Refers to the previous comments made during
the previous meeting it seems that other WG participants
prefers the usage of other mechanism to deliver such
capability.

Kireeti Kompella: Agrees

Rohit Dube: People that oppose may not necessarily be here

Rahul Aggarwal: Will send another mail for discussion in
order to see where in which direction this i-d has to go
after this meeting.

==========================================================

2) Kunihiro Ishiguro (15 Mins): OSPFv3 Traffic Engineering
Extensions
http://www.ietf.org/internet-drafts/draft-ishiguro-ospf-ospfv3-traffic-01.txt

Summary:
- Using the proposed framework, proposes an intra-area
  TE LSA with function code 10, flooding scope is area
  wide scope, u bit set to 1, thus if the router does not
  understand LSA it must be flooded anyway.
- OSPFv3 TE TLV, katz i-d used as a base. TLV thus
  the router address and the link TLV are considered
  here for the OSPFv3 router LSA.

Acee Lindem: There is an alternate proposal to be
discussed thus comments to come after.

Alex Zinin: Router id related question - reachable
address because it can be signalled thus what are
the signalling implication related to the proposed
change?

Kunihiro Ishiguro: Not sure at this moment and depends
upon the implementation.

Kireeti Kompella: Does IPv6 provide a addressable and/or
reachable address?

Kunihiro Ishiguro: Depends upon the implementation

Kireeti Kompella: Take for instance, BGP over ipv6 what
do you advertize as the next hop?

Acee Lindem: It can be the router-id in IPv4.

Kireeti Kompella: Router address TLV has been proposed
to sync up ISIS and OSPF topologies, and as used in BGP
today (to connect BGP with an incoming LSP request), the
missing thing here is that links can be unnumbered and
thus the point of the router id (the router address that
it identifies) is that it needs to be globally unique or
defined as unique wide address or sometimes it may be
routable thus the same thing is needed with v6.

Kunihiro Ishiguro: This comes from the traffic engineering
implementation and or BGP, here a "stable IP address is
not needed" but for traffic engineering purposes it seems
to be.

Alex Zinin: WRT to OSPFv3 it seems that we change the
semantic of the protocol, in OSPFv2, this address is a
reachable IP address, in ipv6 this is not the case, thus
if things are different they should be kept separate in
order to maintain the consistency and the semantic of the
ospfv3 protocol.

Acee Lindem: Questions about the semantic of the router-id.

Kireeti Kompella: This is the router address TLV.

==========================================================

3) Acee Lindem (5 Mins): OSPF Hitless Restart Update
http://www.ietf.org/internet-drafts/draft-ietf-ospf-hitless-restart-03.txt
note: version -04.txt posted to list

Summary:
-------

- Hitless restart i-d of J. Moy, Acee Lindem acts as editor
  for this document and has an implementation for the
  interoperability testing. Padma Pillary-Ensault is
  also an author with an implementation.

- Changes from 03->04
  . Grace period restricted to the LSA refresh time
  . Alternative to saving crypto seq numbers in non-volatile
    storage
  . Alternate help mode termination (ignore LSA changes under
    configuration control)
  . Always flood to 224.0.0.5 in the case of unplanned restart
    which is important since a router loses the knwoledge of
    being previsouly elected as a designated router
  . Remove mospf, from future work and add less conservative
    helper termination

- Proposed change:
  Add alternative to apply the grace LSA to all neighbor adjacencies
  for orinating router (Padma Pillay-Esnault). This only applies
  to the case where there are parallel adjacenncies - appears to be
  fully compatible as long as the grace LSA is flooded on all
  interfaces.

Discussion:
----------

Acee Lindem: Thus ready for last call? Will re-issue the draft
for comments and wait a couple weeks.

Alex Zinin: Interoperability tests available?

Acee Lindem: Redback is interoperable with Juniper (not tried
the Moy's implementation), Force10 also has an implementation.

Padma: Implementation between Juniper and Force10 tested.

==========================================================

4) Kireeti Kompella (10 Mins): OSPFv2 Opaques in OSPFv3
http://www.ietf.org/internet-drafts/draft-kompella-ospf-opaquev2-00.txt

Summary:
--------

1. OSPFv2 compared to the OSPFv3 opaque LSA format

2. Proposal to migrate OSPFv2 opaque to OSPFv3, Use new
   OSPFv3 LSA type, everything else remains the same; the
   LSA ID is the same and the opaque LSA info is the same.

3. Issue with the backdoor problem - yes this
   is a backdoor but why it is a problem?

4. Related question? Is OSPFv3 for IPv6 (only) or an
   improvment of OSPFv2? Thus we should be able to run
   an IPv4 network with OSPFv3?
   - If so OSPFv3 is a superset of OSPFv2
   - If not remove all the IPv4 prefix infromation
     from v3

   Consider OSPFv3 as superset of OSPFv2
   - Then we can migrate properly from v2 to v3
   - If not all sorts of functions will break during
     the migration

   Alternative:
   - Define a new lsa function for each of the opaque
     LSA type: one for TE LSA, one for the grace LSA,
     etc.
   - What's the length of the opaque id? 24 or 32 bits?
     But this would break the migration

5. Conclusion

   Pros and cons for v2 opaque lsa in v3
   - Pros: Code reuse v3 includes v2, migration
   - Cons: Theoritcal backdoor issue
   Pros and cons for translating opaque lsa one-by-one
   - Pro:?
   - Con: Would make the migration less pragmatic

   Next steps: We need to understand what's this backdoor
   problem is weight, the pro and cons and make a pragmatic
   decision (to have an opaque LSA ready code)

Discussion:
----------

Alex Zinin: Questions about OSPFv3 for IPv4?

Acee Lindem: Not described in the current RFC

Alex Zinin: Thus not to be used for the arguments?
since this is an orthogonal problem: announce IPv4
information using OSPFv3 does not make sense

Kireeti Kompella: The inverse is done today

Alex Zinin: Do we agree?

Kireeti Kompella: Yes

Alex Zinin: Opaque type?

Kireeti Kompella: Opaque LSA, this is a v2 opaque LSA

Alex Zinin: Have a single level of numbering

Kireeti Kompella: This implies to change the code - do
you know how long it takes?

Alex Zinin: Yes and i try to simplyify the code we use

Kireeti Kompella: The code to use is very simple, look
at the opaque type...

Alex Zinin: What's problem we try to solve?

Kireeti Kompella: New opaque type in OSPFv3 and useful for
OSPFv2 as well since I do not want to change my code for
interoperability reasons

Alex Zinin: No difference between the two proposals, thus
which one to select

Kireeti Kompella: Want to do it once (for all)

Alex Zinin: With the proposal you grab the function code
in OSPFv3, the only difference here is, v2 in v3, by doing
that you create an overlap specification space and please
think about the implication

Rohit Dube: OSPFv3 for IPv6 is a different protocol from v2
in terms of a model it should be considered as different
protocols.

Kireeti Kompella: Thus OSPFv3 not used for IPv4

Alex Zinin: Thus we don't use it for discussion

Kireeti Kompella: Make a statement, if the protocols are
different then state this in the corrresponding document

Rohit Dube: Could you clarify your point

Kireeti Kompella: Since IPv4 in OSPFv3 is not specified,
I will make the clarification in order to allow for that;
by analogy, RSVP can use IPv6 identification over IPv4
everything is ready except the OSPFv2 document while
people ask this from my side, thus this is a real problem
and not a theoretical problem as the backdoor one.

Alex Zinin: The working group should decide what to do,
but Alex's concerns with this approach is that it will
create potential problem while not solving the intended
problem - thus a cleaner approach should be provided.

Acee Lindem: This is not a brand new application thus
I agree with Alex.

Alex Zinin: Things must always be specificed

Kunihiro Ishiguro: type 9 is already used by v2,

Kireeti Kompella: Types 9, 10, and 11 map in the
value 22 in v3, meaning it is a v2 opaque LSA, but
the backdoor problem is there anyway

Rohit Dube: This problem will be further discussed on
the mailing lists as well the respective merits of the
two approaches.

==========================================================

5) Jerry Ash (10 Mins): Congestion Avoidance & Control for
OSPF Networks
http://www.ietf.org/internet-drafts/draft-ash-manral-ospf-congestion-control-00.txt

Summary:
--------

1. Introduction: Draft addresses the problem of scalability;
   Evidence is failure experience, vendors analyzing their own
   OSPF implementations, and analysis of the LSA storms

2. Background and motivation

3. Failure experience: failure experience in 4/13/98 in the
   ATT frame relay network.

4. Proposed protocol mechanism: Signal a congestion state,
   to become to a specific OSPF protocol processing during
   the congestion detection, the neighbors will be notified
   about the slowdown and adjust the flooding rate.

5. Lot's of discussion on the list - is there a problem? We
   feel there is a problem.

   Initiate a debate on how to solve the problem, the
   protocol is complete as it is, and these problems will be
   resolved by having better implementations but operators
   asks for interoperable implementations this is the reason
   for these i-d's.

   Thus proposal to go beyond this and go to a procedure for
   that purpose? The proposed congestion response is analogous
   to the helper router response to a 'grace LSA' from a congested
   router in hitless restart.

   Concerning the approach of better coding? does it solves
   the problem but in the mean time we think that the better
   standard between vendors would be to solve these issues

Discussion:
----------

Padma: Concerning the protocol extensions, grace LSA is not
necessarily applicable since a restarting router is not a
(necessarily) a congested router; are these to be considered
as real protocol extensions (like for instance the throttling)
or just more fine tuned implementations?

Jerry Ash: The congested router would signal its congestion state
before it saturates, this would reduce congestion by slowing down
the neighbor LSAs sent to the congested router.  These mechanisms
are considered as protocol extensions: the neighbor response to
the congestion notification is analogous to the helper router response
to the 'grace LSA' from a congested router in hitless restart.

Rohit Dube: Move discussions after the second presentation

Acee Lindem: But keep track of the charter concerning the
hello and ack prioritization.

==========================================================

6) Gagan L. Choudhury (10 Mins): Explicit Marking and
Prioritized Treatment of Specific OSPF Packets for
Faster Convergence and Improved Network Scalability and
Stability
http://www.ietf.org/internet-drafts/draft-ietf-ospf-scalability-02.txt

Summary:
-------

1. Basic issue: failures in the network generating sustained
   CPU usage, LSA storms, and positive feedback loops.

2. Proposal: Priority for the hello and the ack's
   the question is how to deliver it, ask for having
   this as BCP, for instance diffserv codepoints for
   high priority and another for low priority.

3. Simulation study: Three priority scenarios, and two
   network scenarios, tested with 2 LSA scenaros.

   Show graphic(s) on the non converged LSA's vs the LSA
   storm (in seconds) to represent the strenght of
   the LSA storm (the actual curves)

   Show graphic(s) illustrating that priority allows for
   pacing the storm but until a certain threshold only
   and if the usage of priority for acks is also provided
   this theshold is higher.

   In all cases, the usage of priorities there is an
   improvement for the sustainted cpu usage.

4. Proposal: Use of special marking (at least a to become
   a BCP) and use of it for the prioritization of hellos.

Discussion:
----------

Gagan Choudhury: Should we move to the next one?

Acee Lindem: yes

==========================================================

7) Gagan L. Choudhury (10 Mins) LSA Flooding Optimization
Algorithms and their Simulation Study
http://www.ietf.org/internet-drafts/draft-choudhury-manral-flooding-simulation-00.txt

Summary:
-------

1. How to improve this threshold significantly?

2. Basic issue: in very large networks an LSA
   storm a sustained cpu congestion may appear.

3. Flooding algos to be considered:
   - algo1: LSA flooding over all interfaces
   - algo2: LSA flooding over only one interface
            for parallel adjecencies
   - algo3: full flooding at mp relays to the immediate
            neighbors

Alex Zinin: algo3 does not guarantee the reliability of
the flooding

   - algo4: flooding only along a minimum spanning tree
   - algo5: algo2 for non-te (topological) LSA's and
            algo4 for the te LSA's

Alex Zinin: We can't use all of them or a selection

4. Simulation results:

   . Presentation of the five different cases each
     analyzed with the allowed LSA storm size

   . Observations on the flooding algorithms

5. Conclusion: algo2, algo5 and modified algo5 should
   be pursued further

Discussion:
----------

Alex Zinin (as WG member): algo5 doesn't appear to be
robust, can you explain in which context you propose it?

Gagan Choudhury:?

Alex Zinin (as WG member): An ATM switch fails, while the
IP router is unaware of the routing topology, how does it
work?

Gagan Choudhury: Network watches for any link and node
failure but here we speak about the flooding link (...)

Alex Zinin: Referring to previous mailing list discussion,
flooding trees generates problem when a single link fail,
there is a lot of topology activity here, raising potential
multiple trees

Gagan Choudhury: During the failure, basic LSA's can carry
the needed information

Alex Zinin: Which LSA's are flooded?

Gagan Choudhury: Only the ones that are strictly needed

Alex Zinin: It is not always safe to say there is no topology
info exchange with more efficient flooding algo's, resyncing
neighbors may be heavy... something equivalent to ISIS

Acee Lindem: Basic flooding paradigm with proposed techniques
seems reasonable but anything beyond this is questionable?

Gagan Choudhury: Agrees

Acee Lindem: Explicit marking, as specified in RFC 1812, says
all OSPF packets should be sent at Internet Control level. If
something new is proposed, it must be precisely specified.

Gagan Choudhury: Agrees, BCP and explicit marking needs more
details

Rohit Dube: To be a bit stronger, priority of hellos,
acks, use of other packet for the reset timer; all of
these can be done without any protocol changes, to be
abstracted and added as a WG i-d; everything else should
be included in a separate document,

Gagan Choudhury: Agrees

Jerry Ash: Not only a BCP but also needs for an explicit
notification mechanism.

Rohit Dube: BCP talks about hellos and acks, and this
seems to be agreed, everything requiring protocol changes
(such as flooding) should be discussed separately.

Jerry Ash: Proposed to start with the ECN (Explicit Congestion
           Notification)

Rohit Dube: Propose a vote concering the ECN

Acee Lindem: (describing the consensus) Clearly more people
against.

Padma Pillay-Esnault: Understand the congestion problems but
most of these are related to bugs and implementation issues,
the extensions are not really implementation-based solution
since they can generate other problems; thus proposes to take
them in offline discussions to be tackled by the implementation.

Alex Zinin: EC notification and EC detection also needs
mailing list discussion, people are afraid of specifying
the implementation details, and believe that we don't
have to go to these two extremes, (bits on the wire only
versus implementation details), Alex would like to open
the discussion concerning these very dynamic behaviors.

==========================================================

Rohit Dube: charter update
===========================

Summary:
-------

Charter update has been sent out on the list

Selection criteria are as follows:
- Rough consensus on the list
- Technical quality of these i-ds
- Urgency of the item
- Charter proposal pending for a bit (queue up)

Done things:
-----------
- OSPF for IPv6
- NSSA update
- OSPF-TE extensions

To do list:
----------
- See proposal

Dropped:
-------
- MOSPF
- OSPF flooding reduction

Note: To be reconsidered in case of strong need

Discussion:
----------

Alex Zinin: IPv6 meeting today on "site local" issues. Site
            border work not needed for now.

Rohit Dube: Will submmit the chrter to these i-ds

Acee Lindem: New items will be added or removed per
evaluation criteria.
** end of the meeting **