The definition I'm using is on P. 242-243. I'm not sure there is a conflict. You're interpreting "data" in your sentence to mean "payload," I'm not sure this is the case. Assuming the book does not contradict itself, looking at the definition on
P.242-243, I would guess that "data" in your sentence means "the stuff in the link layer frame [including the header]." But it's not very precise language so maybe I'm wrong and the book does contradict itself.
<br><br><div><span class="gmail_quote">On 9/20/07, <b class="gmail_sendername">Jonathan D. Ellithorpe</b> <<a href="mailto:jde@berkeley.edu">jde@berkeley.edu</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Ah very interesting. That is why you and I are saying different things.<br><br>On page 339 of the textbook it says:<br><br>"The maximum amount of data that a link layer frame can carry is called<br>the maximum transmission unit (MTU)."
<br><br>Which conflicts directly with:<br><br>"MTU is the length of the largest link-layer frame that can be sent by<br>the local sending host"<br><br><br><br>Nescio Nomen wrote:<br>> Is it defined for packets or for frames? I'm finding conflicting
<br>> definitions on google. The book says that the MTU is the "length of<br>> the largest link-layer frame that can be sent by the local sending<br>> host"-- hence my confusion since we're not provided any link layer
<br>> header info. But, if I understand what you've said earlier, we're to<br>> assume it's strictly going to only have IP header anyway.<br>><br>> On 9/20/07, *Jorge Ortiz* <<a href="mailto:jortiz@cs.berkeley.edu">
jortiz@cs.berkeley.edu</a><br>> <mailto:<a href="mailto:jortiz@cs.berkeley.edu">jortiz@cs.berkeley.edu</a>>> wrote:<br>><br>> The MTU is the largest sized packet that can be passed. This includes<br>
> header information.<br>><br>><br>> On 9/20/07, Nescio Nomen <<a href="mailto:nescionomen@gmail.com">nescionomen@gmail.com</a><br>> <mailto:<a href="mailto:nescionomen@gmail.com">nescionomen@gmail.com
</a>>> wrote:<br>> > Oh wait, I think I understand-- you're saying that MTU does not<br>> include the<br>> > link header size?<br>> ><br>> ><br>> > On 9/20/07, Nescio Nomen <
<a href="mailto:nescionomen@gmail.com">nescionomen@gmail.com</a><br>> <mailto:<a href="mailto:nescionomen@gmail.com">nescionomen@gmail.com</a>>> wrote:<br>> > > I'm not sure I understand. (in a real life problem) why
<br>> wouldn't we need<br>> > to know the size of the frame header just because we are given<br>> the MTU?<br>> > Wouldn't we try to find the amount of 'real data' that could fit
<br>> by doing<br>> > something along the lines of MTU - frame header size - IP header<br>> size -<br>> > Layer 4 header size?<br>> > ><br>> > ><br>> > >
<br>> > > On 9/20/07, Jonathan D. Ellithorpe < <a href="mailto:jde@berkeley.edu">jde@berkeley.edu</a><br>> <mailto:<a href="mailto:jde@berkeley.edu">jde@berkeley.edu</a>>> wrote:<br>> > > > I think the MTU is actually defined as being the maximum
<br>> amount of data<br>> > > > that a link layer frame can encapsulate. Thus, we don't need<br>> to consider<br>> > > > the size of the frame, since we're just given the MTU of the
<br>> link-layer.<br>> > > ><br>> > > ><br>> > > > Jorge Ortiz wrote:<br>> > > > > On 9/20/07, Nescio Nomen <<a href="mailto:nescionomen@gmail.com">
nescionomen@gmail.com</a><br>> <mailto:<a href="mailto:nescionomen@gmail.com">nescionomen@gmail.com</a>>> wrote:<br>> > > > ><br>> > > > >> For hmwk Problem #2, P16, do we know if the datagram will
<br>> have a TCP<br>> > header<br>> > > > >> inside? (Is it necessarily the case that a datagram always<br>> > encapsulated a<br>> > > > >> TCP header?)
<br>> > > > >><br>> > > > ><br>> > > > > If it's specified as only being a plane datagram (as it is<br>> in the<br>> > > > > problem), we only need to include the IP header.
<br>> > > > ><br>> > > > ><br>> > > > >> Also, when we are transmitting into the link, how big is the<br>> > > > >> frame header?<br>> > > > >>
<br>> > > > ><br>> > > > > Treat the packet as having only an IP header and the data<br>> you wish to<br>> > send.<br>> > > > ><br>> > > > >
<br>> > > > >> We haven't really talked about this layer yet. Does the<br>> size<br>> > > > >> of the frame header depend on the technology, i.e. optical?<br>> > > > >>
<br>> > > > ><br>> > > > > It may, yes. Different mediums may have different header<br>> definitions.<br>> > > > ><br>> > > > > jorge<br>
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