[j-nsp] Limit on interfaces in bundle

[Saku Ytti]

On 30 October 2015 at 12:35, Jesper Skriver <jesper at skriver.dk> wrote:

Hey Jesper,

> That would not be practical to implement for a router, implementations
> typically have the L2 header cached and the L3 forwarding
> constructs just point to a rewrite object that contain the
> appropriate L2 encap for the next-hop selected by L3.
>
> What you are proposing means that a single L3 object needs to
> point to different L2 rewrite objects depending on what L2 encap
> was on the packet when received.  Many architectures just cannot
> do that, and for others it would for sure come at a performance
> penalty.

I'm surprised by this. Because LSR today could have single interface,
which egresses native IPv4, IPv6, ARP, or MPLS, depending on ingress.
And I know 7600 offers ethertype in egress rewrite information, so it
could impose any ethertype as lookup result.
Obviously high-touch platforms like ASR9k, MX, 7750SR, CX600/NE40
could also do any type of egress ethertype.
In the proposed scenario, LSR would not change the ethertype, if it
came in as MPLS-IP, it would go out as MPLS-IP, ingress LER would
decide ethertype.

I'm not surprised that there would be some platforms where this
limitation exists, but I would have guessed those are very restricted
L3 switches which already have many limitations, such as not
supporting control-word etc.

-- 
  ++ytti