Re: [pim] pim wg adoption call for draft-chen-pim-srv6-p2mp-path-01

[Huaimo Chen <[e-mail]>]

Hi Acee,

    Thank you very much for your comments.
    My responses are inline below with prefix [HC].

Best Regards,
Huaimo

I think the concept of the ingress node encoding the complete MDT in the segment
list is flawed and won’t scale. At some point, the segment list is finite.
[HC]: In Segment Rouging (SR), for an explicit point-to-point (P2P) path/tunnel
from an ingress to an egress,  the ingress node encodes the path in the segment
list. This should improve the network scalability since there is no per-path state
in the core of the network.
For an explicit point-to-multipoint (P2MP) path/tree (or say MDT),
it seems natural for the ingress node of the P2MP path to encode the P2MP path
in the segment list. This should also improve the network scalability since
there is no per-P2MP-path (or say per-MDT-tree) state in the core of the network.
For a P2MP path/tree, its ingress node does not have to encode the complete
MDT in the segment list. If the tree has a few separated sub-trees from the ingress,
for each of these sub-trees, the ingress node encodes it in a separated
segment list and sends the multicast packet with the segment list for the
sub-tree to the next hop node along the link on the sub-tree.
Regarding to the finite size of the segment list, for a P2MP path/tree,
the tree can be "split" into multiple sub-trees such that each of the sub-trees
can be encoded in the segment list of the finite size.

Additionally, the network programming is fairly complex.
[HC]: The document on the network programming is on its way to be a RFC after WGLC.
With the network programming, a function may be defined by a program/procedure
for a SID or a set of SIDs. It seems easy to add a new function in this way.

Finally, a separate multicast SID must be provisioned and advertised for every
multicast egress or replication node. Please let me know if I’m missing something.
[HC]: A separate multicast SID must be provisioned for every replication node
and a central controller such as PCE knows the SID on the node.
It seems that this is similar to a replication SID for every replication node.
We will update the draft with some details accordingly to address your concerns.


I don’t support WG adoption. For those supporting adoption, I’d ask if you plan to actually implement this.

Thanks,
Acee