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Queston 1: What are the responsibilities of transport layer in TCP/IP

Model?

ANSWER:In TCP/IP Model :

Transport layer delivers a unit of data from the source application tothe destination application.

Delivering data from source application to destination application.

Dividing a message into manageable segments and reassembling it

at the destination.

In OSI Model :

The Transport Layer is responsible for flow and error control, and

also allows for the re-transmit of failed or corrupted packets.

Question 2: What is the difference between network layer delievery

and transport layer delievery.

ANSWER:

In the Network Layer it controls the operation of subnet and it

tells data which route to take.

In the Transport Layer it controls at which speed the data can

be send and it also tells about types of services provided to session

layer.

Question 3:What are headers and trailers and how do they get added

and removed?

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ANSWER:

Header:

An information structure that precedes and identifies the

information that follows, such as a block of bytes in communication.

Trailer:

An innformation typically occupying several bytes, at the tail

stop of a block of transmitted data and often containing a checksum

or other error-checking data adjectives for confirming the accuracy

and status of the transmission.

Addition and Removal of Headers and Trailers:

Headers and Trailers concept is related to the OSI

model. In data communication from one device to another the

"Sender" appends header and pass it to the lower layer while

'Receiver' removes header and passes it to upper layer. Headers are

added at lode 6,5,4,3 & 2 while Trailer is added at layer 2

Queston 4: Suppose a computer sends a packet at the network layerto another computer somewhere in the Internet. The logical

destination address of the packet is corrupted. What happens to the

packet? How can the source computer be informed of the situation?

ANSWER:

Assuming you are using TCP/IP and not UDP, when a packet

gets sent out it has both the destination address and the source

address. Once the destination successfully receives the packet it

send a response back to the source address to say it was successful.

(With UDP - you just send it and dont wait for an acknowledgement

that it got there OK).

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Therefore if the destination address or source address were incorrect,

the source machine would not get a return saying all got through OK.

Normally this would result in the packet being resent after a period oftime.

So assuming we have an incorrect address, the packet will eventually

be delivered to the wrong destination (that system might send back

that it recieved it OK - so that could be a problem - but hopefully it

would ignore it - a bit like I do with letters I dont want to recieve -

depends on firewall policies).

Otherwise it will fail quite quickly when it cant be routed to a host, in

which case you would get an error message back. (Using the source

address).