why am i in this handbasket? (was Devil's Advocate - Segment Routing, Why?)

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Tue Jun 23 11:16:43 UTC 2020


Mark Tinka wrote:

>> But, it should be noted that a single class B...
> 
> CIDR - let's not teach the kids old news :-).

Saying /16 is ambiguous depends on IP version.

>> And, if I understand BGP-MP correctly, all the routing information of
>> all the customers is flooded by BGP-MP in the ISP.
> 
> Yes, best practice is in iBGP.
> 
> Some operators may still be using an IGP for this. It would work, but
> scales poorly.

The amount of flooded traffic is not so different.

>> Then, it should be a lot better to let customer edges encapsulate
>> L2 or L3 over IP, with which, routing information within customers
>> is exchanged by customer provided VPN without requiring extra
>> overhead of maintaining customer local routing information by the
>> ISP.
> 
> You mean like IP-in-IP or GRE? That already happens today, without any
> intervention from the ISP.

I know, though I didn't know ISP's are not offering SLA for it.

> There are few ISP's who would be able to terminate an IP or GRE tunnel
> on-net, end-to-end.
> 
> And even then, they might be reluctant to offer any SLA's because those
> tunnels are built on the CPE, typically outside of their control.

The condition to offer SLA beyond a network of an ISP should not
"trusted NNI" but policing by the ISP with ISP's own equipment,
which prevent too much traffic enter the network.

> If ISP's didn't make money from MPLS/VPN's, router vendors would not be
> as keen on adding the capability in their boxes.

It is like telco was making money by expensive telephone exchangers
only to be replaced by ISPs, I'm afraid.

> Label stacking is fundamental to the "MP" part of MPLS. Whether your
> payload is IP, ATM, Ethernet, Frame Relay, PPP, HDLC, e.t.c., the
> ability to stack labels is what makes an MPLS network payload agnostic.
> There is value in that.

What? You are saying "payload" not something carrying "payload"
is MP.

Then, plain Ethernet is MP with EtherType, isn't it?

						Masataka Ohta


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