How comes a TCP packet doesn't contains the source and destination IPs?

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From here cisco says the TCP packets doesn't contains the source IP and destination IP? how the network layer knows tho thich IP send the packet and who has to get the ack back?

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2012-04-04 17:10
by 0x90


TCP is typically run atop IP, and IP addresses are stored within the IP part of the packet that encapsulates the TCP part.

2012-04-04 17:16
by Kyle Jones
s/typically/always/, no? :- - Celada 2012-04-04 17:16
@Celeda Yah, but I've learned not to say "always" on the Internet - Kyle Jones 2012-04-04 17:26
@Celada Lately you have a good chance at this case but: - Karlson 2012-04-04 17:26
@Celada See? : - Kyle Jones 2012-04-04 17:28
@Karlson I'm glad I made that comment just so that someone could come along and teach me something really obscure :- - Celada 2012-04-04 17:40
@Celada Weirder things have been known to happen. : - Karlson 2012-04-04 18:08
Why is that? I wouldn't have expected a Layer 4 protocol to depend on the Layer 3 protocol. I thought the idea behind the OSI model was that each level says "send this there" and the level under it takes care of how it actually happens. Can you please clarify this in your answer? : - KevinG 2018-05-03 23:46


A TCP packet goes inside of an IP packet. The IP header specifies the source and destination addresses, among other things. See this diagram. Here, the TCP data would be inserted into the data position.

2012-04-04 17:22
by Joel


You are confusing the TCP packet information (transport layer) with the IP wrapper (network layer). The ip address is contained as part of the outer IP packet wrapper.

2012-04-04 17:18
by PinnyM