On Fri, 19 Nov 2021 at 17:12, Thomas Bellman via juniper-nsp <[email protected]> wrote:
> Cut-through actually *can* help a little bit. The buffer space in > the Trident and Tomahawk chips is mostly shared between all ports; > only a small portion of it is dedicated per port[1]. If you have > lots of traffic on some ports, with little or no congestion, > enabling cut-through will leave more buffer space available for > the congested ports, as the packets will leave the switch/router > quicker. Correct, you can save packetSize * egressInts of buffer with cut-through. So if you have 48 ports and we assume 1500B frames, you can save 72kB of buffer space. > One should note though that these chips will fall back to store- > and-forward if the ingress port and egress port run at different I had hoped this was obvious, when I mentioned the percentage of frames getting cut-through. And strictly speaking, it is not 'these chips', you cannot implement cut-through without store-and-forward. You'd end up dropping most of the traffic in all but very esoteric topology/scenario. -- ++ytti _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
