Editing Maximum segment size (section)

==MSS and MTU==
MSS is sometimes conflated with [[Maximum transmission unit|MTU/PMTU]], which is a characteristic of the underlying [[data link layer|link layer]], while MSS applies specifically to TCP and hence the [[transport layer]]. The two are similar in that they limit the maximum size of the payload carried by their respective [[protocol data unit]] (frame for MTU, TCP segment for MSS), and related since MSS cannot exceed the MTU for its underlying link (taking into account the overhead of any headers added by the layers below TCP). However, the difference, in addition to applying to different layers, is that MSS can have a different value in either direction and also that frames exceeding the MTU may cause packets (which encapsulate segments) to be fragmented by the [[network layer]], while segments exceeding the MSS are simply discarded.