[e2e] Port numbers in the network layer?

John Day jeanjour at comcast.net
Wed Apr 24 04:55:54 PDT 2013

After delving into it fairly deeply, it is clear that port-ids are 
the crucial piece required for proper (and useful) layer isolation.

Decoupling port allocation from synchronization as indicated by 
Watson's work is key in constructing a well-formed layer.  Watson 
clearly recognized the importance of distinguishing port-ids (a local 
handle) from Connection-endpoint-ids (CEP-ids that are carried in 

Both the Internet and the OSI Models conflate port allocation and 
synchronization and so have one identifier where two are required. 
Cleanly distinguishing them has major implications for security.  A 
layer without port-ids leads to all sorts of problems, the least of 
which are the so-called protocol-id fields to identify the syntax of 
the encapsulated header.

Take care,

At 12:24 PM -0700 4/23/13, Bob Braden wrote:
>During the development of TCP during the 1977-1980 period, the 
>original C&K  TCP layer was divided into a transport layer (TCP) and 
>an internetwork layer (IP). One of the key decisions in this split 
>was which layer should inherit the port numbers. At the time I 
>simply accepted the group decision to put ports into the transport 
>layer without taking time to think through the architectural 
>implications. Has anyone ever thought through how the architecture 
>would have been changed had ports ended up in the internetwork 
>layer, i.e., in IP?
>Bob Braden

More information about the end2end-interest mailing list