RTT calculations

[Arvind Venkatesan]

Let me state my problem more clearly.

The later part of my click config file looks like this:

Myelement -> EtherEncap() -> ToDevice();

In MyElement I calculate the recd time of the packet by using its
timestamp annotation.
	When I send this packet out from MyElement, I start my clock to
count the next RTT.
The packet goes through EtherEncap and ToDevice before it Really gets on
the wire. 
I somehow have to account for this error! 
		The Average RTT for my experiments is about 20 ms (my
machines are quite close to each other. 
But sometime I see RTT as high as 900 ms. Is ToDevice() contributing to
this?
How much can it delay the sending of a packet, assuming that the line is
100 Mbps.
And the data rate that is coming into the router is about 10 Mbps. (My
router is running on
700Mhz pentium 3 machine).

Thanks a lot!

-arvind

	 
	

-----Original Message-----
From: Eddie Kohler [mailto:kohler at icir.org] 
Sent: Thursday, March 07, 2002 2:19 PM
To: Arvind Venkatesan
Cc: click at amsterdam.lcs.mit.edu
Subject: Re: RTT calculations 


Hi Arvind,

Here are some of the timestamping elements we provide:
- SetCycleCount
- CycleCountAccum
- SetTimestamp

If you want to track elapsed time from the timestamp annotations, you
might have to write your own element. It could be something like
CycleCountAccum. Sounds like a good idea, actually!

Let us know if we can help more.
Eddie