a) Consider a network in which packets are delivered reliable across each link.

Question

a) Consider a network in which packets are delivered reliable across each link. That is, for each pair of adjacent nodes A - B, the datalink layer has an ARQ protocol (such as stop-and-wait) that ensures packets sent by A do arrive at B. In this network, why do you think is necessary for the transport layer to also have its own ARQ protocol and do retransmissions of its packets?

b) For each of the following, identify which OSI layer is responsible for performing the described action:

i) Make sure that a packet is delivered reliably across a single physical link
ii) Describes how a binary tree data structure is to be encoded inside the message
iii) Makes sure that a message is delivered reliably from the source host to the destination host
iv) Coordinates the transmission of multiple flows of data across multiple sources and multiple destinations (for example, a video conference)
v) Defines how the bits are converted into voltages
vi) Decides how a data packet is to be routed from one link to the next.

Explanation / Answer

a) Every layer exchange of messages is different. At data link layer the transfer
of unit of data is called Frame and at the transport layer it is called segments
or datagrams and for relaible transfer each layer should get an ack for whatever it
is trandferring. So the ack at only data link layer is not suffiecient at higher
levels like Transport layer.

b) i) Trnasport layet
   ii) Application layer
   iii) Network layer
   iv) Data link leyer
   v) Physical layer
   vi) Network layer

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.