Re: [Idr] Growing BGP-LS Attribute

[Robert Raszuk <[e-mail]>]

Hi Adrian,

> IMHO, two fundamental concepts in BGP-LS are summarisation and
stability.

I don't see any summarization in the current encoding as most if not all of
the information being sent is verbatim taken from IGP drafts and RFCs.

Stability is also not there as now we have a lot of dynamic data without
any new advertise-time thresholds being set - so we are just relying on IGP
flooding thresholds.

BGP-LS has just one fundamental convenience - free TCP transport. That's
it. If our link state protocols would run over TCP from any node to
controller (well Henk & Gunter  just proposed it for ISIS) or if there
would be a BMP analogy to IGPs (get full or filtered feed of LSDB or TED
over TCP) there would be very limited need for BGP-LS.

So today we are just growing single BGP-LS Attribute. Such attribute
content changes depending if it is part of Node NLRI, Link NLRI or Prefix
NLRI. Say take LInk NLRI there are TLVs which are static and which are
dynamic - well there is no way to only send dynamic when they change as in
BGP subsequent update with the same NLRI is an implicit withdraw of the
former. So you are forced to repeat everything for given link NLRI
regardless if even single value changes. You call this a "summarization" ?

Further imagine controller and operator only needs 10% of the information
for his specific application. Well hard luck as there is no way in general
in BGP to ask for a subset of the attribute content. Neither RTC nor ORF
would be of any use.

What is needed here is an efficient and reliable pub-sub message transport
- not just load of BGP TCP because it is there. And this all applies to
trusted or untrusted or hybrid domain types :).

Cheers,
R.


On Sat, Oct 20, 2018 at 7:17 PM Adrian Farrel <[e-mail]> wrote:

> Robert sed:
>
> > Do we really want to grow this single BGP Attribute even more ?
>
> Time to remind everyone about Yakov's Shakespeare-over-BGP?
>
> IMHO, two fundamental concepts in BGP-LS are summarisation and stability.
> If someone wanted to have access to all of the IGP information and be
> updated every time anything changed, why would they not become a silent
> partner in the IGP? The thing BGP-LS should buy you is the fact that a BGP
> implementation is usually quite good at gathering and correlating routing
> information, and then applying policy to it.
>
> OTOH, it may be that this argument^H^H^H debate was lost some time ago.
>
> But maybe the thing here is for the WG to step back and decide what the
> point of BGP-LS is, how it should grow, and what controls should be in
> place.
>
> A topic for the f2f meeting?
>
> Best,
> Adrian
>
>