[c-nsp] LDPv6 Census Check
bedard.phil at gmail.com
Thu Jun 11 18:50:11 UTC 2020
On 6/11/20, 1:19 PM, "Saku Ytti" <saku at ytti.fi> wrote:
On Thu, 11 Jun 2020 at 19:49, Phil Bedard <bedard.phil at gmail.com> wrote:
> As for normal v6 forwarding, the way most higher speed routers made recently work there is little difference in latency since the encapsulation for the packet is done in a common function at the end of the pipeline and the lookups are often in the same memory space. NPUs are also being built today with enough on-package memory to hold larger routing tables. Whether a packet has to be buffered on-chip vs. off-chip has a much larger impact on latency/PDV than a forwarding lookup.
On-package is not important, on-chip or off-chip is what matters, i.e.
do you eat SERDES to connect memory or not.
Sorry meant to say on-die, not on-package.
Typically the time it takes to do those lookups are built into the system specs to attain the performance you need with deterministic latency within a certain bounds. There are certainly corner cases where you make tradeoffs, especially now that single NPUs are 10+ Tbps, but it's not really an MPLS vs. IPv4 vs. IPv6 thing. The other key is to do those types of accesses in a single pass, not traverse multiple hierarchy levels or do multiple operations. If you are tunneling then the table for any of those types is going to small on a mid-point router.
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