Recaro

For an assignment (due tomorrow) I need to research the layer in the network model that is responsible for the actions undertaken in respect to flow control and sequencing.

Anybody know which layer it is?

cheers

UHF

look up OSI on the internet, its easy to find diagrams showing TCP/IP and the OSI model! And what each of the layers do!

Recaro

done that. But I got two different websites that both say different answers. One says Transport layer and the other says data link

HHxx

Heres a hint

Application
Presentation
Session
Transport
Network
Datalink
Physical

UHF

Its the session layer, its right under the Transport layer so it assumes an establised Poing to Point connection.

[Edited by UHF - 3/17/2003 7:52:34 PM]

HHxx

Oops. you don't need that

UHF

However the Network Layer is responsible for chopping packets up into more managable units based on the MTU of the network.

And the Data Link is responsible for ensuring a reliable connection so it'll retransmit packets etc

Recaro

session layer?!?

Im so confused. Websites say transport layer or data link layer and some one says session layer. So now I have 3 layers it could be.

UHF

Perhaps your question has more context, there are sequence numbers happening at multiple levels for different reasons!

Recaro

Heres the question:

"For ease of transmission a long message is broken down into a number of smaller packets to match the maximum allowabl frame length for a particular network. Each of these are then transmited seperately.

Investigate which layer of the netowrk model is responsible for actions undertaken in respect of flow control and sequencing. refer to both OSI and TCP/IP models."

Any help

UHF

For example a sequence number can be used to identify packet fragments so that a packet can be reassembled at the other end, also packets themselves have sequence numbers (obviously in a different place in the packet header).

Why not draw yourself a packet header and establish what the different layers contribute to the header, that way it'll build up slowly and you can tell your techers/lecturers that the question lacked context so here is a demonstration of how it works, learn it and UNDERSTANDit and hey presto you know OSI, rather than the current method of learning where people are taught to simply memorise stuff rather than actually KNOW it.

I know, I've got a degree in Computer Science and the amount of people who graduated with me who can quote text books to you but cant actually be useful in a IT team was huge!

UHF

"For ease of transmission a long message is broken down into a number of smaller packets to match the maximum allowabl frame length for a particular network. Each of these are then transmited seperately."

This is the MTU (Maximum Transmittable Unit), this is definately handled by the NETWORK layer. This is where packets are broken up into manageable "chunks", they are reassembled at the receiving end and once complete passed as a complete packet to the layer above.

"Investigate which layer of the netowrk model is responsible for actions undertaken in respect of flow control and sequencing. refer to both OSI and TCP/IP models."

They are talking about the session layer here though!

Perhaps they want you to look at both layers and see how they compare in the TCP/IP model, i think you should do the rest yourself

UHF

See here

http://www.ee.duke.edu/Courses/fall/ee156/notes-current/ip.pdf

They talk about fragmentation too here which is what you're first bit is on about which is where you have an MTU smaller than the size of the packet, it gets fragmented and put together later.

Rather like taking a subaru to peices, labelling all of the parts with numbers, posting them and then reassembling them the other end using the numbers!

Corgi

I assure you it's the Transport layer, just done an exam with this question in.

@UHF....a degree in computer science....are you sure!!

UHF

mate the problem is the question "could" be talking about two layers!

Its like these daft GNVQ questions which are where do you plug the keyboard

a). the cpu
b). the monitor
c). the power supply
d). your ***

To which there isnt a realy answer, cos they mean the tower when they say CPU, its screwed!

UHF

AND I checked my old course books, clearly confirms what I said!