[e2e] Routers accessing TCP header

Arjuna Sathiaseelan arjuna at dcs.kcl.ac.uk
Mon Feb 21 04:19:16 PST 2005

Dear Jon,
  Thanks for your appropriate reply. I am basically working on a mechanism
called the Explicit Packet Drop Notification (EPDN). EPDN works like
this : Every router has a hashtable which stores the flow id and the
maximum and minimum sequence numbers of the dropped packets. This
information will then be inserted into a packet of that particular flow
that passes through the gateway successfully. The receiver in turn runs
a series of algorithms to detect whether a missing packet is dropped or
not. Based on this the receiver informs the sender about the cause of
the inorder packet.  We do not maintain per flow state - just the state
of flows of dropped packets.

Now this mechanism infact has lots of limitations such as not incremental
and requires all the gateways to be implemented with the EPDN mechanism
and as you said requires lots of CPU cycles for deep packet inspection.

Do you think this type of mechanism has any future in real world
implementation and do you feel that maintaining the max and min sequence
numbers of dropped packets is a possibility given that there is IP
fragmentation going on?

Your suggestions will be really helpful..


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