[ee122] HW1: 2b clarification

Jorge Ortiz jortiz at cs.berkeley.edu
Tue Sep 18 21:32:47 PDT 2007


On 9/18/07, Simon Tan <simtan at berkeley.edu> wrote:
> Hi,
>
> I was under the impression that a 'one-way delay' included transmission
> delay (as well as processing, queuing, and propagating delays) in one
> compact, convenient number for our calculations. At least, that is the
> definition I find by searching and asking around.

It includes processing, queuing, and propagation delay, but there is
still a transmission delay that's dependent on the available bandwidth
which you should take into account.

>
> If the '40 ms' that was referenced only applies to RTT (which, I also
> presumed, was round-trip time, the sum of two one-way delays and
> neglecting the factor of 'response time'), then I would have to calculate
> some other number to multiply by my number of packets, wouldn't I?

Yes (as I hinted above).

>
> What of part (c) of the question - it is using RTT again, so do we go back
> to  basing the answer on '40ms'?

Yes.

>
> Thanks for any clarification of "one-way delay", "RTT", and "time to
> transmit" you can provide.

I hope that cleared it up some of the confusion.  If you have more
specific questions, feel free to drop by my office hours tomorrow from
1-2pm.

Jorge

>
>
>
>
>
> On Tue, 18 Sep 2007 07:41:24 -0700, Jorge Ortiz <jortiz at cs.berkeley.edu>
> wrote:
>
> > Just apply it to the RTT.
> >
> > jorge
> >
> > On 9/18/07, Merry Choi <merry_c at berkeley.edu> wrote:
> >> Some further clarification about the definition of 40ms delay.
> >>
> >> Does this mean, say if, a packet could theoretically be sent in 15ms in
> >> the
> >> given bandwidth, it would take 40ms for it to actually send? Or rather,
> >> this
> >> delay is only applicable to the calculation for the RTT.
> >>
> >>
> >> --Merry
> >>
> >>
> >> -----Original Message-----
> >> From: ee122-bounces at ICSI.Berkeley.EDU
> >> [mailto:ee122-bounces at ICSI.Berkeley.EDU] On Behalf Of Jorge Ortiz
> >> Sent: Monday, September 17, 2007 8:04 AM
> >> To: sylvainla at berkeley.edu
> >> Cc: ee122 at ICSI.Berkeley.EDU
> >> Subject: Re: [ee122] HW1: 2b clarification
> >>
> >> On 9/17/07, Sylvain La <sylvainla at berkeley.edu> wrote:
> >> > In Homework 2, part b, the question states that we wait an RTT after
> >> > transmitting a packet. Does this mean we wait the RTT (about 80 ms)
> >> > immediately after sending out the last bit of a packet, or do we wait
> >> until
> >> > a packet is received on the other end before waiting an RTT (about
> >> 120 ms)
> >> ?
> >>
> >> After you're done acually
> >> If you start counting your wait time after you have received an
> >> acknowledgement, how long have do you actually wait?
> >>
> >> >
> >> > -Sylvain
> >> >
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>
>
> --
> ~Simon Tan >> undergraduate at UC Berkeley
> Source: simtan at berkeley.edu
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