> On Mar 2, 2015, at 9:07 AM, Steven Barth <cy...@openwrt.org> wrote:
> 
> 
>> One thing that has been mentioned to me is that IS-IS could be used (with 
>> proper TLV additions) to completely replace HNCP, if IS-IS were used as the 
>> homenet protocol. If true should we be calling this out more explicitly in 
>> the document?
> I got my hands on ISO 10589 today and tried to very briefly glance through 
> it. And personally I had a really hard time getting into it.

Yes. ISO standards are not always the best place to get an overview of things. 
:)

The document referred to here is ISO10589:2002.

Section 6.8 is an overview IS-IS link-independent stuff. (pages 12-14)

Section 7 gets into specifics but skip anything about level 2 (definitely skip 
partition repair), at least to start, as we are only considering level-1 
single-area operation. Feel free to skip over (or quickly glance through) any 
address specific stuff (7.1) as it mostly does not pertain. Also skip anything 
related to hosts for now (ES or end-systems, i.e., ISO hosts).

7.2 The "Decision Process" (pages 18-26)

This is basically an SPF with bi-directional checks (both sides of a link refer 
to each other). Additionally the fact that a broadcast network is treated as a 
pseudo-node with routers (non-pseudonodes) attached to it (rather than a 
full-mesh of connections between routers) is important.

So 7.3 is the update process (advertising and flooding of information). (pages 
26-45)

Primarily this is going to get into
- How a router advertises it’s information (LSP generation)
- How IS-IS makes sure things are flooded (using sequence number packets and 
internally 2 flags called SRM and SSN).
- LSP expiration and collision detection.

Feel free to skip 7.4 (forwarding process), 7.5 (constants and parameters).

Section 8 is the link dependent stuff. Here the hello protocol is documented. 
Skip ES (end-system stuff).
- P2P (pages 50-54)
- Skip 8xxx
- Broadcast (pages 59-63)

Section 9 documents the protocol (on-the-wire) encodings (page 65-92)

Everything else can be skipped (page 92 on).


> Having read the comparison document beforehand I haven't found anything about 
> IPv4, IPv6, HMACs, wide-metrics or other things that are mentioned in the 
> draft (and that ISO standard was ~200 pages already).

There’s a new version that has the references to the RFCs for v4, v6, hmac and 
wide metrics.

The core of the IS-IS protocol is contained in about 80 pages. From above you 
should be able to get an good idea of the protocol in about ~40 pages, although 
it won’t necessarily be easy reading. :)

> So I think I asked Mikael the same thing already but could you (or anyone 
> else) please provide a dumbed down specification or at least an overview 
> document that references all relevant ISO-standards, RFCs and drafts (or 
> chapters thereof) that one needs to read to understand modern IS-IS?
> On top of that if you could mention what could / or should be removed for a 
> trimmed down homenet version that would be a huge plus.

Basically a trimmed down version is "level-1" operation only (everything in a 
single area). Whenever something mentioned level-2 operation discard it.

Thanks,
Chris.

> 
> 
> Cheers,
> 
> Steven
> 
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