Jonathan Woolley wrote:
Jumbo frames aside from the usefulness of bigger payload for mpls/tunnels etc add some value in an environment where there's some packet loss.
I would have thought it makes it worse, assuming a physical fault resulting in a constant bit error rate combined with larger packet size means higher probability that a packet is corrupted (as there are more bits in it). The resulting packet is discarded which is a bigger loss than discarding a smaller one.
For example in an environment with say a 1Gbps link where packet loss is .1% with 1500 byte MTU you get 28Mbps througput. With Jumboframes that leaps to approx 162Mbps.
Can I see the maths behind this? If you're talking about packet loss due to congestion and not using TCP then you're probably right
I assume he's talking about my TFRC math from http://wand.net.nz/~perry/max_download.php Assuming you've saturated your link, a one bit in 'n' is going to take out one packet every so often (if it takes out more than that you're not going to get anything much worth discussing over your link in the first place). So increasing the MTU isn't going to make it more likely that a packet is lost, it just means you need to retransmit a larger packet. However, since you're using larger MTU's, it's going to take you less RTT's to get back up to full speed on your link, and therefore your link will spend more of its time going at full rate than if you had a lower MTU (since it would require more RTT's at lower throughput before it starts saturating the link again).