Please explain how you got this: 1.544Mbps = 192KB/sec
----- Original Message -----
From: Arun Upadhyay <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, October 10, 2000 8:34 PM
Subject: Re: CCIE question about buffers being used up on router
>
> Hi Priscilla
> I found the solution.
>
> Here it is:
> 1.544Mbps = 192KB/sec
> Router begins to forward at the rate of 64KB/sec
> means it is tranfering at the rate of 3 packets/sec
> i.e it will take 1/3 sec. or 333 ms to transfer one
> packet.
>
> Now it's getting packets at the rate of 5000
> packets/sec i.e one packet in every 1/5000 sec. or
> 1000/5000 = .2 ms
> so it will get 500 packets in 500x.2=100 ms
>
> So by the time router will forward first packet in
> 333ms, it's buffer will be full.
>
> Thanks for your help.
>
>
> --- Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote:
> > Oops. I was multiplying 512 bits times 5000 bits per
> > second. I guess I lost
> > a digit. Sorry.
> >
> > Now it's a much more interesting problem!
> >
> > Priscilla
> >
> > At 06:22 PM 10/10/00, Brian wrote:
> > >On Tue, 10 Oct 2000, Priscilla Oppenheimer wrote:
> > >
> > > > At 12:01 PM 10/10/00, Arun Upadhyay wrote:
> > > > >Can anybody please help in solving this
> > problem?
> > > > >
> > > > >A router is connected to a T1 line which has
> > the
> > > > >maximum speed of 1.544mbps. The router begins
> > to
> > > > >forward 64bkps packet at 5000 packets per
> > second,
> > > >
> > > > Do you mean 64-byte packets? If you convert that
> > to bits it's 512 bits.
> > > > 5000 packets of that size per second is 560,000
> > bits per second, which
> > > is a
> > > > lot less than 1.544 Mbps so not much buffereing
> > will be needed at all. You
> > > > could have just one buffer and no packets should
> > ever get dropped.
> > >
> > >Priscilla,
> > >
> > >How did you come up with 560,000 bits per second?
> > Can you break that down
> > >for me, I know I must be doing something wrong:
> > >
> > >64bytes * 8 = 512 bits
> > >512 bits * 5000 packets = 2560000 bits
> > >
> > >brian
> > >
> > >
> > >
> > >
> > > >
> > > > >there are 500 buffers available.
> > > >
> > > > How big are the buffers? Can we assume they are
> > 64 bytes also?
> > > >
> > > >
> > > > >Approximately how
> > > > >long before the link is complelety saturated,
> > the
> > > > >buffers are full and the router begins to
> > discard.
> > > >
> > > > If you are trying to get help with questions
> > like this that appear on the
> > > > CCIE written test and practice exams, you will
> > want to give us an example
> > > > of where the WAN link is oversubscribed. For
> > example, if the offered load
> > > > to the WAN link is 110% more than the WAN link
> > could handle, 500 buffers
> > > > would get used up in about 5000 packet times. (I
> > think? Comments anyone?)
> > > >
> > > > In reality, packets don't arrive at a constant
> > rate, so much more
> > > difficult
> > > > math and queuing theory is required, and that
> > goes beyond the research and
> > > > thinking I'm willing to do right now. &;-)
> > > >
> > > > Priscilla
> > > >
> > > >
> > > >
> > > > > Thanks.
> > > > >
> > > > > Arun
> > > > >
> > > > >=====
> > > > >Arun Upadhyay
> > > > >SE Engineering
> > > > >MCSE CCNA CNA
> > > > >
> > > >
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> > > > ________________________
> > > >
> > > > Priscilla Oppenheimer
> > > > http://www.priscilla.com
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> > >-----------------------------------------------
> > >Brian Feeny, CCNP, CCDP [EMAIL PROTECTED]
> > >Network Administrator
> > >ShreveNet Inc. (ASN 11881)
> >
> >
> > ________________________
> >
> > Priscilla Oppenheimer
> > http://www.priscilla.com
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>
> =====
> Arun Upadhyay
> SE Engineering
> MCSE CCNA CNA
>
> __________________________________________________
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