Silence on the Wire

Segment Size Roulette

One of the less obvious and hence less popular ways to detect packet rewriting devices and learn more about network configuration is analyzing the maximum segment size field in incoming traffic.

Because IP packet fragmentation adds noticeable overhead to the fragmented traffic, it is often perceived as a performance nightmare, and many implementers try to prevent it. On the other hand, as discussed earlier, fragmentation is difficult to eliminate, as it seems to be nearly impossible to accurately, quickly, and reliably determine the maximum transmission unit (MTU) over a path in advance of actual communications. Even the best method available, path MTU discovery, is far from perfect and still impacts performance when triggered. ...