Hello all,
Gunter van de Velde (Nokia) and me have been working
on 2 ideas to improve the scalability of IS-IS flooding
in large-scale data-center networks.
One idea deals with reducing IS-IS flooding in dense topologies.
Next week or so we'll publish a draft that explains this idea.
It's a distributed algorithm, backwards compatible, no extra
computations required, works in any topology, has redundancy.
The other idea is simpler.
This afternoon Gunter and myself have published a draft about it.
You can find it here:
https://datatracker.ietf.org/doc/draft-hsmit-lsr-isis-flooding-over-tcp/
Abstract:
This document proposes a solution to use TCP for IS-IS flooding. The
proposed solution is a relative simple extension to implement. IS-IS
flooding over TCP brings BGP's property of scalable transport via TCP
to Link-State protocols.
This proposal defines a new TLV in point-to-point IIHs to signal the
intent of a router to do flooding over TCP, and it defines a small
header to encapsulate IS-IS PDUs in the TCP byte-stream.
The idea is simple:
- Routers include a new TLV in IIHs to indicate that they want to
flood over TCP.
- When both routers agree, (both have the new TLV included) the router
with the lowest systemid opens a TCP connection to its new neighbor.
- This TCP connection is used to send LSPs and SNPs over.
- IIHs are still sent the classic way (directly in a layer-2 frame).
- Flooding over TCP is only done on p2p interfaces, not on multipoint
ifs.
There are several benefits for IS-IS:
- the IS-IS process does not need to send or receive SNPs (acks)
- the IS-IS process doesn't need to do retransmissions of LSPs
- multiple LSPs can be packed into fewer TCP segments
- TCP will bring high throughput and flow-control to IS-IS flooding
Of course, all feedback is welcome,
Gunter & Henk
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