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Does the MTU of a TCP packet include the TCP & IPv4 headers?

Tags:

tcp

ip

mtu

Or: What is the maximum payload size for a TCP/IPv4 packet.

Much appreciated!

Cheers.

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James Avatar asked Feb 05 '12 17:02

James


People also ask

What is included in MTU?

The IP MTU is the total size of all information that is included with the packet. This includes the header, and the data payload to transmit. The IP and TCP header takes 40 bytes.

How MTU is calculated?

In our case MTU value = MSS + IP header + ICMP header. Now let's add 28 bytes reserved for the data header (20 bytes for the IP header and 8 bytes for the ICMP request header) to the number obtained during the test. Thus, for our example, MTU=1472+28=1500 bytes (this is the optimal value for the MTU parameter).

What does MTU depend on?

In many cases, MTU is dependent on underlying network capabilities and must be adjusted manually or automatically so as to not exceed these capabilities. MTU parameters may appear in association with a communications interface or standard. Some systems may decide MTU at connect time, e.g. using Path MTU Discovery.

What determines TCP packet size?

The packets get merged on arrival at the receiving network. The maximum size of a TCP packet is 64K (65535 bytes). Generally, the packet size gets restricted by the Maximum Transmission Unit (MTU) of network resources. MTU is the maximum size of the data transfer limit set by hardware in a network.


2 Answers

The MTU of an IP packet is the entire packet, including all IP and higher level headers (such as TCP headers) and payload. Lower level headers (such as Ethernet frames) are not included since they're not IP's concern. However the actual MTU value is influenced by the lower levels, as there's usually a limit, and IP has to stick to it.

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Matti Virkkunen Avatar answered Oct 13 '22 20:10

Matti Virkkunen


MTU = IP Header + Tcp Segment

MSS = Data(doesn't include TCP header)

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Vikash kumar Avatar answered Oct 13 '22 21:10

Vikash kumar