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Re: recent internet packet size samples

  • From: Yu Ning
  • Date: Sun Jul 30 21:06:29 2000 
----- Original Message ----- 
From: "Mark Milhollan" <[email protected]>
To: <[email protected]>
Sent: Friday, July 28, 2000 1:41 AM
Subject: Re: recent internet packet size samples 


> 
> Bill Woodcock writes:
> >
> >    > I'm interested in seeing the distribution of packet sizes across a
> >    > 1500-byte-constrained measurement point, with "real internet traffic"
> >    > going past (for some reasonable interpretation of that phrase).
> >
> >Protocol         Total  Flows   Packets Bytes  Packets Active(Sec) Idle(Sec)
> >--------         Flows   /Sec     /Flow  /Pkt     /Sec     /Flow     /Flow
> >Total:       758613841  176.6         2  1170    440.8       6.1      14.6
> 
> I.e., on cisco routers with "Flow switching" enabled on all interfaces
> you want data included from, the router will give you that ...
> 
> >show ip cache flow
> IP packet size distribution (1242M total packets):
>    1-32   64   96  128  160  192  224  256  288  320  352  384  416  448  480
>    .001 .436 .050 .018 .012 .008 .006 .005 .004 .005 .004 .006 .004 .003 .004
> 
>     512  544  576 1024 1536 2048 2560 3072 3584 4096 4608
>    .003 .003 .071 .030 .318 .000 .000 .000 .000 .000 .000
> [...]
> Protocol         Total    Flows   Packets Bytes  Packets Active(Sec) Idle(Sec)
> --------         Flows     /Sec     /Flow  /Pkt     /Sec     /Flow     /Flow
> [...]
> Total:        55814697     43.4        22   581    965.3       5.1       7.9
> 
> Indeed, if you use the export mechanism you can capture the details
> behind this summary and analyze it pretty much as you like.
> 
> #ip flow-export destination cflowd-machine
> #ip flow-export version 5
> 
> 

It seems the packets size varied greatly, the first one is 1170, the second
is 581, while I sample my core network, and get 290. 

You will find there is some discrepancy between the direct result 581, and
if you calculate probability size from the packets distribution:

distribution:
32 64 96 128 160 192 224 256 288 320 352 384 416 448 480 512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
0.001 0.436 0.05 0.018 0.012 0.008 0.006 0.005 0.004 0.005 0.004 0.006 0.004 0.003 0.004 0.003 0.003 0.071 0.03 0.318 0 0 0 0 0 0

respective size: (multiply the two roles above respectively)
0.032 27.904 4.8 2.304 1.92 1.536 1.344 1.28 1.152 1.6 1.408 2.304 1.664 1.344 1.92 1.536 1.632 40.896 30.72 488.448 0 0 0 0 0 0

probability size (sum the line above up):
615.744                         

the error is: 615.744-581 = 34 bytes


I have a question, how to get the packets size stat from a GSR? We know dcef
is enable default in GSR, can we use dcef to get the stat ?


thanks!
------------------------------------------------------
(Mr.) Yu(2) Ning(2)
Int'l/Domestic Routing/Resource Man.
ChinaNET(AS4134) Backbone Operation Center
Networking Dep.,Datacom Bureau, China Telecom.
Beijing,P.R.C +86-10-66418105/66418121/66418123(fax)
------------------------------------------------------