From: Usankin, Andrew (Andrew.Usankin@twtelecom.com)
Date: Fri Oct 19 2007 - 12:41:24 ART
Very good question indeed. I used to thing that packet will go through
but now I'm going to dig dipper to make double sure it is.
For now, here is what I got from labbing:
R1#sh run int s1/0
Building configuration...
Current configuration : 129 bytes
!
interface Serial1/0
ip address 172.16.1.1 255.255.255.0
serial restart-delay 0
traffic-shape rate 32000 3200 3200 1000
end
R1#sh traffic-shape s1/0
Interface Se1/0
Access Target Byte Sustain Excess Interval Increment
Adapt
VC List Rate Limit bits/int bits/int (ms) (bytes)
Active
- 32000 800 3200 3200 100 400 -
R1#ping 172.16.1.2 size 1500
Type escape sequence to abort.
Sending 5, 1500-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/282/412
ms
R1#
As you can see, bytes limit per interval is 800 and I'm sending packets
of 1500+24 bites size. They all make it through.
Andrew
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Gregory Gombas
Sent: Thursday, October 18, 2007 7:27 PM
To: Eric Phillips
Cc: ccielab@groupstudy.com
Subject: Re: Effect of shaping with small Bc, no fragmentation, and a
large packet?
I didn't mean it literally, I just meant that since the packet will
always be exceeding bc it can never be sent...and thus dropped.
Only way to know for sure is to lab it up!
On 10/18/07, Eric Phillips <ephillips@squick.cc> wrote:
> Thanks everyone for the replies, I definitely appreciate it!
>
> I did skip a 0 there, sorry... I was aiming for a 10ms Tc to make
> VOIP traffic delayed as little as possible. So yes, the Bc would be
640 bits.
>
> Herbert, my numbers were referring to Shaping, so I was keeping
> everything in bits. With policing you deal in bytes.
>
> I am very intrigued to see that we have three answers, so perhaps I am
> not the only one that is a bit confused by this. If it is queued
> forever, does it block the pipe while it is queued?
>
> -Eric
>
>
>
> On 10/18/07, Gregory Gombas <ggombas@gmail.com> wrote:
> >
> > Even with shaping configured, if the router queues the packet then
> > it would be queued indefinately considering it will always be larger
> > than bc and never be able to send it...
> >
> > On 10/18/07, Herbert Maosa <asawilunda@googlemail.com> wrote:
> > > Eric,
> > >
> > > I assume you are maintaining bytes as the unit for Bc and ms as
> > > the unit
> > for
> > > TC ? In that case Bc of 64 Bytes and Tc of 10ms is giving me CIR =
> > 512Kbps,
> > > using the formula CIR = Bc/Tc.
> > >
> > > In any case, what will happen to a packet that is larger than the
> > maximum
> > > rate permitted will depend on whether you are shaping or policing.
> > > If
> > you
> > > are shaping, then the packet will simply be queued in the shaping
> > > queue
> > from
> > > which it will then be sent at CIR. If you are policing then it
> > > will
> > depend
> > > on the configured action for non-conforming traffic.
> > >
> > > Herbert.
> > >
> > >
> > > On 10/18/07, Eric Phillips <ephillips@squick.cc> wrote:
> > > >
> > > > Hi all,
> > > >
> > > > I have searched through the GroupStudy archives, read through
> > > > Odem's
> > DQOS
> > > > book, and checked out the DOC CD, but have not found a clear
> > > > answer to
> > a
> > > > question that has been on my mind.
> > > >
> > > > If I enable shaping with a very small Bc, for example, a Tc of
> > > > 10, and
> > a
> > > > Bc
> > > > of 64, that should shape to 64kbit/sec, right? Now if I do not
> > > > enable link fragmentation, and a large packet, perhaps 1400
> > > > bytes comes through,
> > what
> > > > will happen? It can not be sent in a single Tc, and it can not
> > > > be fragmented because link fragmentation is disabled. Also
> > > > assume that I have no Be, or a Be too small to allow 1400 bytes
> > > > to accumulate between Bc
> > and
> > > > Be.
> > > >
> > > > This seems like an awfully simple question, but I have not found
> > > > a
> > clear
> > > > answer anywhere.
> > > >
> > > > Thank you very much,
> > > >
> > > > Eric
> > > >
> > > >
> > ____________________________________________________________________
> > ___
> > > > Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > > >
> > >
> > >
> > >
> > > --
> > > Kindest regards,
> > > hm
> > >
> > > __________________________________________________________________
> > > _____ Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
>
> ______________________________________________________________________
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