4 ms·
In practice the "split path" scenario is only a problem when topology changes. Routers typically use a hash of source and destination port, source and destinati
by mitchs 8y ago
In practice the "split path" scenario is only a problem when topology changes. Routers typically use a hash of source and destination port, source and destination IP address, and sometimes ingress port id to pick which of N equal paths to take.
This is done not just to preserve end destination, but so every sequential packet in a flow follows the same path, thus must arrive in the same order. (Different paths have different latencies because of distance and buffer depth on the routers.) Many tcp implementations will back way off as soon as they see out of order packets, so network providers must do this.
- deleted 8y ago[deleted]
- userbinator 8y agoRouters typically use a hash of source and destination port, source and destination IP address, and sometimes ingress port id to pick which of N equal paths to take. ...and sometimes even the TTL, as evidenced by this recent news item: https://news.ycombinator.com/item?id=17893594 https://news.ycombinator.com/item?id=17893594
- mitchs 8y agoInteresting, thanks for the link. Note to self, customers don't keep consistent ttls... Yikes.