Subject: Re: IP-in-TCP?
To: Seth Kurtzberg <>
From: Jason Thorpe <>
List: tech-net
Date: 02/02/2005 08:50:13
On Feb 1, 2005, at 11:16 PM, Seth Kurtzberg wrote:

> If he really means tunneling IP through TCP, that would be essentially 
> the same as the UDP case.  If he means an IP layer that can be used 
> just like any other IP layer (meaning you could have nested TCP) then 
> I agree that you have a mess.

No, tunneling IP trough TCP is a lot different than tunneling IP 
through UDP.

UDP is a datagram protocol, just like IP is.  That means it will have 
the same network dynamics as IP.  The downside is that you need to 
reduce the MTU of the encapsulated IP datagram so that the outer UDP 
datagram is not fragmented.

TCP, on the other hand, is a stream protocol.  This lets you use a full 
e.g. Ethernet MTU on the inner packet.  But, because of the outer TCP's 
flow control, you are going to have very different network dynamics for 
the inner-IP.  These different dynamics often come with performance 

-- thorpej