Hi Tom, I came across your draft "Scale-Up Network Header (SUNH)" and found it very interesting and timely. It resonated well with a draft I wrote a while ago (https://datatracker.ietf.org/doc/html/draft-song-ship-edge-05) although that one addressed a more general scope. Here are some comments and thoughts I'd like to share.
1. "Some traffic patterns may have a majority of small packets, like for KV cache in AI, where packet sizes may commonly be 256 bytes or less." As far as I know, the token KV cache is pretty big and the packet size is limited by the MTU. The small packets in Scale Up network are usually for control plane signaling and synchronization, or small memory-semantic transactions. Anyway, I agree the header overhead is a big concern in AIDCN and the current SUE solution is flawed. 1. There's no dedicated Scale Up Network NICs available. Scale Up network interface is usually supposed to be integrated into the GPU dies. When Ethernet interface is used, the situation might change. But a GPU cannot afford to have two PCIe interfaces to connect two separate NICs. So most likely the scale up and scale out networks will be converged and share the same NIC. If that's true, compatibility and the ability to interoperate with standard IP protocols become a necessity. 1. I think 16-bit SUNH address is too long for now, and probably too short in the future if the scale up and scale out networks are converged. So it's better to maintain flexibility. The SHIP draft I mentioned earlier provides a flexible scheme and allows the gateway switches to translate the header-compressed packets into normal IPv4/v6 packets so the inter-DC traffic can be seamlessly supported. With this, the routing header (i.e., compressed SRv6) can also be supported, making the scheme even more flexible to support SR (in another research, I found that capability is very useful in certain DCN topologies). I think this is an area and opportunity that IETF can contribute to the AI network, and I'm looking forward to contributing to it. Best regards, Haoyu
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