Hello Tom -
Sorry if I am being a bit dense, but ... routing in datacentres replaced
Ethernet switching to provide capabilities such as fast reroute,
improved scalability, improved network management, etc which SUNH
doesn't seem to address.
If SUNH is only about reducing packet overheads, what value does SUNH
provide versus using Ethernet without *any* network header?
/bill
On 2026-01-15 2:57 p.m., Tom Herbert wrote:
On Thu, Jan 15, 2026 at 11:27 AM Bill Gage <[email protected]> wrote:
Please excuse my ignorance, but ... modern Ethernet switches have MAC
address table sizes on the order of hundreds of thousands of entries.
Building a local switched (not routed) network using a hierarchy of
Ethernet switches appears to be a common practice.
Hi Bill,
Larger networks, like in hyperscalers, are more likely to be L3
switched than spanning tree. There is also a know problem with
Ethernet that it lacks a hop limit.
So what problem does SUNH solve?
1. It reduces the size of the network layer header to reduce
on-the-wire overhead
2. A smaller address simplifies switching and address lookups
Tom
/bill
On 2026-01-09 5:53 p.m., Tom Herbert wrote:
On Fri, Jan 9, 2026 at 2:03 PM dave seddon <[email protected]> wrote:
Now that the context is established, explain why 16 bits were chosen
for the source/destination address. I guess, but it's not in the
document; You were considering the number of hosts in the domain.
The numbers being thrown around for scale-up networks seem to be a
couple of thousand nodes at most. 16 bits nicely rounds to the power
of two and allows plenty of space to scale to reasonably large GPU
clusters. Also, for scale-up we anticipate pretty flat networks with
may two or three hops at most (justifies smaller Hop Limits in the
protocol).
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