MTU vs MSS: Solving Packet Fragmentation and Speed Issues

In networking, size matters. If your data packets are too large for a link to handle, they must be broken into pieces. This process, called Fragmentation, causes massive overhead and kills performance.

Maximum Transmission Unit (MTU)

The MTU is the largest size of a packet (including headers) that can pass through a network link. The standard for Ethernet is 1500 bytes.

Maximum Segment Size (MSS)

While MTU handles the whole packet, MSS deals specifically with the TCP data payload. It is usually MTU minus the IP and TCP headers (1500 - 40 = 1460 bytes).

The Solution: MSS Clamping

Most modern routers use "MSS Clamping" to automatically shrink the MSS during the TCP handshake, ensuring all packets fit through the path without fragmentation.