Polytechnic University, Dept. Electrical and Computer Engineering
Multimedia Communication System II
Fall 2005, Yao Wang
Homework 8 Solution (Networking - Basics)
What are the four major components that constitute the Internet?
The computers (or hosts) at the network edge, the routers at the network core, the transmission media that
link the computers and routers, and the protocols that govern the data transport among computers through the
What are the five protocol layers of the Internet? What are their primary functions?
The five layers are application,
transport, network, link, and physical. The application layer
govern the client-server interactions among hosts in different applications. Different application layer
protocols have been established for different applications. The transport layer protocols govern the transfer
of data from one host to another in any particular application. There are two types of transport layer
protocols, TCP and UDP. TCP is for connection-oriented data transfer, governs session set-up, error control,
flow control, and congestion control. The UDP protocol is for connection-less data transfer, and merely adds
a port number to the payload data.
The network layer primarily performs network packet routing following
different routing protocols. It also performs packet fragmentation when necessary subject to a maximum
packet size, and error control at the network layer. The link layer refers to data transfer over individual links
in a chosen route and it has corresponding protocols governing link layer error control. The physical layer
refers to the actual transmission media (fibers, cables, wireless, etc) and various functions at that layer.
What is connectionless service? What is connection oriented service?
With connectionless service, data are sent from a source to a destination without establishing a connection in
advance, (i.e. no acknowledgement from the destination that it is ready and willing to accept the data). The
sender does not attempt to monitor whether the data are delivered to the destination. With connection
oriented service, a connection between the sender and destination is first established through a handshaking
process (i.e., the sender does not send until it knows that the destination is ready to receive the data). Only