Devil's Advocate - Segment Routing, Why?

Sat Jun 20 08:58:28 UTC 2020

On 19/Jun/20 17:40, Masataka Ohta wrote:

>
> As the first person to have proposed the forwarding paradigm of
> label switching, I have been fully aware from the beginning that:
>
>    https://tools.ietf.org/html/draft-ohta-ip-over-atm-01
>
>    Conventional Communication over ATM in a Internetwork Layer
>
>    The conventional communication, that is communication that does not
>    assume connectivity, is no different from that of the existing IP, of
>    course.
>
> special, prioritized forwarding should be done only by special
> request by end users (by properly designed signaling mechanism, for
> which RSVP failed to be) or administration does not scale.

I could be wrong, but I get the feeling that you are speaking about RSVP
in its original form, where hosts were meant to make calls (CAC) into
the network to reserve resources on their behalf.

As we all know, that never took off, even though I saw some ideas about
it being proposed for mobile phones as well.

I don't think there ever was another attempt to get hosts to reserve
resources within the network, since the RSVP failure.

>
> Not. Even without MPLS, fine tuning of BGP does not scale.

We all know this, and like I said, that is a current concern.

>
> However, just as using plain IP router costs less than using
> MPLS capable IP routers, BGP-only administration costs less than
> BGP and MPLS administration.
>
> For better networking infrastructure, extra cost should be spent
> for L1, not MPLS or very complicated technologies around it.

In the early 2000's, I would have agreed with that.

Nowadays, there is a very good chance that a box you require a BGP DFZ
on inherently supports MPLS, likely without extra licensing.

Mark.