[mpls-linux-general] delay Difference at Ingress and Egress

[nitin p. <tac...@ya...>]

Hi James,

Recently I measured the processing delay caused
protocol stack at Ingress, Egress and core.

Here are my results:
Ingress: 3.665 ms
Egress: 0.035 ms
Core: 0.018 ms
IP:0.023 ms

It makes sense that processing time at these nodes
will be in the following order

Ingress >= Egress > Core

What I am wondering, is huge delay at Ingress. If we
do L3 lookup + L2.5 forwarding even then it doesn't
clearify the reason of huge value. Can you please
explain in short how processing is taking place at
Ingress and how it can explain this delay.

Let me also explain my measuring technique, you can
corect me on this if I am doing something wrong.

      ---e1[Node]e0------

In this I am running tcpdump/tethereal at both e0 and
e1. What I have understood is that libcap(used by
tcpdump/tethereal) captures the packet at device
driver, which is after it has been processed by
protocol stack for outgoing packet and before being
processed by protocol stack for incomming packet.  

Thanks and Regards,
Nitin

	
					


    




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