Re: bgp4-17 Section 9

[Yakov Rekhter <[e-mail]>]

Alex,

> Tom,
> 
> > 9.1.2 Route selection now allows for the best route in
> > Loc-RIB not to be placed in the Routing table; how does this
> > impact on the principle (2 Introduction) that a BGP Speaker
> > should only advertise routes it itself uses?  Is it enough
> > for the route to be in Loc-RIB and not in the Routing Table?
> 
> The principle implies that the route is both in Loc-RIB and
> in the routing table, i.e., it needs to be both selected as
> the best and used by the router.
> However, we can only specify so much about the routing table,
> as it is (strictly speaking) outside of the scope of the BGP
> protocol and administrator do have the "filter" rope in
> their hands. Section 3.2 also talks about this.
> 
> > I believe the paragraph on immediate next hop should
> > cross-reference the one in 5.1.3; and the latter allows
> > route lookup to resolve to a subnet and not an immediate
> > next hop address, a possibility 9.1.2 appears not to cater
> > for.
> 
> Fine with me.
> 
> > Perhaps the information on immediate next hop in 5.1.3 and 9
> > should be combined in one place; 5.1.3 would be my
> > preference.
> 
> Fine with me.
> 
> > 9.1.2.1 Intermediate network address throws me each time as
> > I start thinking of networks; I assume that this is the
> > immediate next hop of Rte1; if so, would not that be
> > clearer?
> 
> The address in Rte1 can be either a direct next-hop or
> a third party next-hop (not really a next hop from the RT
> perspective). "Intermediate" should account for both cases.
> 
> > Resolvability talks of routing table entries for IGP and
> > directly connected networks; for consistency with 3.2, I
> > would like to see static in there as well.
> 
> I actually thought about it when writing this text, but
> it fell out of my head. How about this:
> 
>    BGP routes do not refer to interfaces, but can be resolved through
>    the routes in the Routing Table that can be of both types. IGP routes
>    and routes to directly connected networks are expected to specify the
>    outbound interface. Static routes can specify the outbound
>    interface, or the intermediate address, or both.

done.

> 
> > 9.1.2.2e  Again 5.1.3 impacts on this;should this be
> > 'immediate next hop' as opposed to 'next hop' (or NEXT_HOP!)
> > and what happens with a recursive lookup?  Which of the
> > metrics in the various Routing Table entries gets used?
> > Perhaps 'The interior cost of a route is the metric in the
> > routing table for the immediate next hop (see 5.1.3)'
> 
> In fact, "next hop" should read as NEXT_HOP. The metric
> is the IGP cost found in the route resolving the NEXT_HOP.

done.

Yakov.