OSPF WG meeting - Thursday 22nd of november - 15:00-17:00

=========================================================
Reported by: Dimitri Papadimitriou

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/draf
t-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/draf
t-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/draf
t-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/draf
t-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/draf
t-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/draf
t-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 scenarios.

   Show graphics on the non-converged  LSAs Versus time as a function of the 
strength of the LSA storm (one curve for each LSA storm).  There is an 
upper limit or threshold of LSA storm that the network can live with 
without causing sustained CPU congestion.

   Show table illustrating that in all cases priority for Hello 
increases the LSA storm threshold that the network can sustain.  I In 
addition, if priority is given to LSA Ack as well then the LSA storm 
threshold is increased even further.  Also, with priority for Hello the 
adjacency is not declared down even under heavy CPU congestion.

4. Proposal: Prioritization of Hello and LSA Ack is proposed as a BCP.  One 
way of doing this would be to use one diffserv codepoint for higher 
priority OSPF packets and another diffserv codepoint for lower priority 
OSPF packets.  Another way would be to look at the packet headers of 
incoming OSPF packets and queue higher and lower priority OSPF packets 
separately.


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/draf
t-choudhury-manral-flooding-simulation-00.txt

Summary:
-------

1. How to improve the LSA Storm threshold
   significantly?

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

3. Flooding algos to be considered: 
   - algo1: LSA flooding over all interfaces
   - algo2: LSA flooding over only one interface for parallel 
adjacencies
   - algo3: Full flooding only at Multipoint relays that are a subset of 
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 
   - algo5: algo2 for LSAs carrying intra-area topology info and algo4 for 
"other" LSAs.  A modified algo5  also considered that makes the 
flooding links for  "other" LSAs survivable under single link failure and  
single node failure (using dual spanning trees)

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:
     Algorithm 2 gives substantial improvement over Algorithm 1, 
Algorithm 3 provides marginal improvement over Algorithm 2, 
Algorithms 4 and 5 provide substantial improvements over Algorithm 2. 
Modified Algorithm 5 is in between Algorithms 5 and 2.  Algorithm 4 is not 
robust under failures and should not be considered.

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: In algo5 all LSAs carrying topology info would be 
flooded to all neighbors all the time. "Other" LSAs may not reach 
destination temporarily in case the minimum spanning tree is broken. They 
may be reflooded after the minimum spanning tree is repaired.  


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: ATM Network is typically designed to be able to carry 
traffic under single link and single node failure. Our modified algo5 
makes the flooding link for "other" LSAs survivable under single link and 
single node failures. 

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: Full flooding is only for the ones that are strictly 
needed.  This includes "Router" and "Network" LSAs.  "Other" LSAs are 
flooded over spanning tree. 

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.