[c-nsp] Devil's Advocate - Segment Routing, Why?

[Robert Raszuk]

Saku,

What you are saying is technically true but not realistically important.

Why - the answer is history of PTX.

It was originally designed and architected on the very basis of hardware
cost and performance when you would only need to switch at rates MPLS.

Well real world showed that you can't sell such box and IP switching has
been added to data plane there.

Bottom line - I doubt you will find any vendor (from OEM to big ones) which
can afford to differentiate price wise boxes which would do line rate MPLS
and any thing less then line rate for IP. And as such IP clearly brings a
lot of value for simplification of control plane and route aggregation and
IMHO is a good (well best) universal transport today for all types of
services from WAN via Campus to DCs (or even MSDCs).

Cheers,
R.








On Fri, Jun 19, 2020 at 9:36 AM Saku Ytti <saku at ytti.fi> wrote:

> On Thu, 18 Jun 2020 at 22:25, Benny Lyne Amorsen via cisco-nsp
> <cisco-nsp at puck.nether.net> wrote:
>
>
> > > I don't understand the point of SRv6. What equipment can support IPv6
> > > routing, but can't support MPLS label switching?
>
> > This probably does not change anything for SRv6, as that too will likely
> > be an extra cost license. It makes non-MPLS tunnelling solutions very
> > attractive though, since you can get away with a very "cost-effective"
> > core and only require smarts in the edge.
>
> This is simply not fundamentally true, it may be true due to market
> perversion. But give student homework to design label switching chip
> and IPv6 switching chip, and you'll use less silicon for the label
> switching chip. And of course you spend less overhead on the tunnel.
>
> We need to decide if we are discussing a specific market situation or
> fundamentals. Ideally we'd drive the market to what is fundamentally
> most efficient, so that we pay the least amount of the kit that we
> use. If we drive SRv6, we drive cost up, if we drive MPLS, we drive
> cost down.
>
> Even today in many cases you can take a cheap L2 chip, and make it an
> MPLS switch, due to them supporting VLAN swap! Which has no clue of
> IPV6 or IPV4.
>
> --
>   ++ytti
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