[c-nsp] LDPv6 Census Check

Thu Jun 11 16:49:12 UTC 2020

Just to clarify the only routers who potentially need to inspect or do anything with those headers are endpoints who require information in the extension header or hops in an explicit path.  In the simple example I gave, there are no extension headers at all.  

I'm pretty agnostic to IPv6 SR-MPLS and SRv6, but just want to clarify that.  

I'm not going to claim inserting/swapping v6 extension headers is what all routers made in the last 20 years are especially good at.  (  But it's not impossible to do it in some shipping devices today at wire rate with deterministic latency.  

As for normal v6 forwarding, the way most higher speed routers made recently work there is little difference in latency since the encapsulation for the packet is done in a common function at the end of the pipeline and the lookups are often in the same memory space.  NPUs are also being built today with enough on-package memory to hold larger routing tables.   Whether a packet has to be buffered on-chip vs. off-chip has a much larger impact on latency/PDV than a forwarding lookup.      

Thanks, 
Phil 

On 6/11/20, 5:07 AM, "NANOG on behalf of Nick Hilliard" <nanog-bounces at nanog.org on behalf of nick at foobar.org> wrote:

    Saku Ytti wrote on 11/06/2020 05:51:
    > Unfortunately SRv6 is somewhat easy to market with the whole 'it's
    > simple, just IP' spiel.
    it's not "just IP": it's ipv6 with per-router push / pop operations on 
    ipv6 extension headers, i.e. high touch in areas which are known to be 
    deeply troublesome on hardware.

    In this regard alone, the specification is problematic enough that it's 
    unearthed a bug in the IPv6 standard (rfc8200).

    Nick