Re: hub-spoke topology and response time

Hi Mihai,

Just a total guess here but I'm thinking internal interrupt scheduling
w/in IOS. Likely the broadcast traffic is left in the CPU waiting
room a little longer on the receiving end relative to the unicast
traffic.

Sorry for the late reply but I have a few thousand backlogged messages
yet to go and it doesn't appear as if you ever got any other response...

Regards,

Scott

On Jul 2, 2009, at 6:11 , mihai.grigore_at_orange-ftgroup.com wrote:

> Fellow experts,
>
> I have a simple topology: R5 is hub and R1, R3 are spokes.
> IP range is 155.1.0.x/24 where x=router number.
> I am using static FR mapping
>
> R5#sh fram map
> Serial0/0 (up): ip 155.1.0.1 dlci 501(0x1F5,0x7C50), static,
> broadcast,
> CISCO, status defined, active
> Serial0/0 (up): ip 155.1.0.3 dlci 503(0x1F7,0x7C70), static,
> broadcast,
> CISCO, status defined, active
>
> I have a question: why unicast and broadcast response times are so
> different?
>
> For unicast, I have about 57 ms:
>
> R5#pi 155.1.0.1
>
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 155.1.0.1, timeout is 2 seconds:
> !!!!!
> Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60
> ms
> R5#pi 155.1.0.3
>
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 155.1.0.3, timeout is 2 seconds:
> !!!!!
> Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60
> ms
>
>
> For broadcast, I have almost double:
>
> R5#pi 255.255.255.255
>
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to 255.255.255.255, timeout is 2
> seconds:
>
> Reply to request 0 from 155.1.0.3, 88 ms
> Reply to request 0 from 155.1.0.1, 100 ms
> Reply to request 1 from 155.1.0.3, 88 ms
> Reply to request 1 from 155.1.0.1, 100 ms
> Reply to request 2 from 155.1.0.3, 113 ms
> Reply to request 2 from 155.1.0.1, 125 ms
> Reply to request 3 from 155.1.0.3, 116 ms
> Reply to request 3 from 155.1.0.1, 128 ms
> Reply to request 4 from 155.1.0.3, 116 ms
> Reply to request 4 from 155.1.0.1, 128 ms
>
>
> Not a big deal, but anyone tell me why this?
>
> TIA, MIhai
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Tue Jul 21 2009 - 15:42:25 ART