Skip to main content

Home Maximum segment size

Maximum segment size

(also MSS)

Maximum segment size definition

Maximum segment size is a parameter of the TCP (Transmission Control Protocol) that specifies the largest amount of data, in bytes, that a device can receive in a single TCP segment.

See also: TCP Wrapper, TCP handshake, network congestion, network segment

Dangers associated with MSS

  • Fragmentation. If the MSS is set larger than the Maximum Transmission Unit of any network segment along the path, it can lead to IP fragmentation, which can cause inefficiency in data transmission and packet loss.
  • Reduced throughput. An incorrectly set MSS (for example, too small) can lead to a high overhead from TCP and IP headers relative to the data payload. This results in reduced throughput, as more packets are required to transmit the same amount of data.
  • Increased latency. Excessive fragmentation leads to increased latency. More packets means more processing. Plus, each packet incurs processing overhead at each hop along its route.
  • Network congestion. Larger packets occupy more buffer space in network devices, contributing to congestion.
  • TCP performance issues. If the MSS is not optimized for the network, it negatively impacts the performance of flow control mechanisms, leading to substandard network utilization.
  • Security concerns. Hackers exploit fragmentation via certain types of network attacks (e.g., fragmentation overlap attacks).