Devil's Advocate - Segment Routing, Why?

Mark Tinka mark.tinka at
Sun Jun 21 07:52:38 UTC 2020

On 21/Jun/20 00:54, Sabri Berisha wrote:

> That will be very advantageous in a datacenter environment, or any other
> environment dealing with a lot of ECMP paths. 
> I can't tell you how often during my eBay time I've been troubleshooting
> end-to-end packetloss between hosts in two datacenters where there were at least
> 10 or more layers of up to 16 way ECMP between them. Having a record of which
> path is being taken by a packet is very helpful to determine the one with a crappy
> transceiver.
> That work is already underway, albeit not specifically for MPLS. For example,
> I've worked with an experimental version of In-Band Network Telemetry (INT)
> as described in this draft:
> I even demonstrated a very basic implementatoin during SuperCompute 19 in Denver
> last year. Most people who were interested in the demo were academics however,
> probably because it wasn't a real networking event.
> Note that there are several caveats that come with this draft and previous
> versions, and that it is still very much work in progress. But the potential is
> huge, at least in the DC.

Alright, we'll wait and see, then.

> That's a different story, but not entirely impossible. A probe packet can
> be sent across AS borders, and as long as the two NOCs are cooperating, the
> entire path can be reconstructed.

Yes, for once-off troubleshooting, I suppose that would work.

My concern is if it's for normal day-to-day operations. But who knows,
maybe someone will propose that too :-).


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