Match the following: Item List I Match List II a. Application layer 1. TCP b.…

Concept

In a layered network architecture every protocol is placed at the layer whose service it performs. Application-layer protocols define how user-level programs exchange data with one another; transport-layer protocols provide end-to-end, process-to-process delivery across the network; network-layer protocols handle host-to-host addressing and the computation of routes across interconnected networks; data-link-layer protocols frame bits and control delivery over a single directly connected link.

Applying the rule to each protocol

1. Application layer: HTTP is the request-response protocol that web clients and web servers use to exchange documents and other resources, so it belongs with the user-level programs at the top of the stack. Application layer takes match 3.

2. Transport layer: TCP provides a connection-oriented, reliable, in-order byte stream between two processes, adding sequence numbers, acknowledgements, retransmission and flow control on top of an unreliable network. Transport layer takes match 1.

3. Network layer: BGP is the path-vector routing protocol by which autonomous systems advertise reachability and select inter-domain paths, and computing routes between networks is a network-layer function. Network layer takes match 4.

4. Data link layer: HDLC is a bit-oriented link-control protocol that delimits frames with the 01111110 flag, applies bit stuffing and runs the link-level error and flow control over one hop. Data link layer takes match 2.

Cross-check

BGP messages are themselves carried inside a TCP connection on port 179, which is why BGP is occasionally listed at the top of a strict TCP/IP implementation stack. In this matching question the classification follows the function performed, and inter-domain route computation is network-layer work. Reading the assignments back, each entry of List II is consumed once and none is left over:

The pairing is therefore a-3, b-1, c-4, d-2.