[e2e] Reordering in routers

abhijit abhijit at engr.colostate.edu
Fri Aug 8 14:45:05 PDT 2003

Hi all,
I am studying the packet-reordering problem over the Internet from the point 
of view of the routers being a reason of reordering.

In the paper by "Packet Reordering is Not Pathological Network Behavior" by 
Bennet, Partridge, and Shectman, the router queuing structure was said to be 
the reason behind the reordering observed at MAE-east. The DEC gigaswitch used 
at MAE-east point used hunt groups i.e. collection of ports together acting as 
input ports that caused the packets getting distributed and hence reordered.

I am studying queuing architectures and queuing disciplines of present 
routers. But I do not find any routers with parallel input queuing sothat 
incoming packets are distributed over a number of queues before getting 
processed. It will be great if anybody can give me information or pointers 
over this problem, especially:
1. Are the internal structure issues i.e. queuing architectures (input, output 
queues, VOQ, VIQ etc), disciplines (packet scheduling or buffer management 
schemes) responsible or can be responsible for reordering?
2. Or the external reasons such as route flapping, multi-path routing, 
parallel links between two routers, etc. are more responsible for reordering 
happening in the present Internet?

I appreciate any information shared on this problem.

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