Routing and Switching I (ECE 764)

Homework # 1

Syed Shahzad Ali

Zeeshan Gya

Owais

Q1: Define an "Internetwork"

Answer:

An Internetwork is a collection of individual networks connected by intermediate networking devices that function as a single large network.

Q2: Describe the difference between WANs and LANs in terms of:

Size

Transmission Technology

Speed

Devices

Answer:

LAN	WAN

Size
LANs are typically confined in the same building or campus of upto a few kilometers in size. LANs, being restricted in size, have a small worst-case transmission time, which is known in advance. This makes it possible to use certain types of designs that would otherwise not be possible.	Span a large geographical areas, often a country or continent.
Transmission Technology
LANs often use a single cable to which all of the machines are attached. The commonly used types of cables are coaxial cable, twisted pair cable, and fiber optic cable. They commonly use CSMA/CD or Token Passing broadcast topologies.	The transmission technology in WANs consists of transmission lines and switching elements. The transmission lines carry bits from one machine to another, and the switching elements choose an appropriate outgoing line when data arrives on an incoming line, based on the destination. The transmission lines are often PSTN(Public Switched Telephone Network) or leased lines. They normally use point-to-point non-broadcast topologies.
Speed
Traditional LANs operate at 10 or 100 Mbps. Also, gigabit ethernet operates at 1 Gbps. So they have normally higher transmission rates as compare to WANs.	Because of the presence of decision making routing logic in the intermediate systems, the transmission lines, and the large geographic size, WANs are slower than LANs and, in general, have greater end-to-end delay. Typical WAN standards T1, T2 and T3 operate at 1.544, 6.312, and 44.736 Mbps respectively.

Devices
Typical LAN interconnection devices include Repeaters Hubs, MAUs, Bridges Switches (Ethernet, Token Ring) Workgroup Concentrators Routers	Typical WAN interconnection devices include Routers Modems CSU/DSU Switches (Frame Relay, X.25, ATM etc.) MUX TA/NT1 (Terminal Adapter/ Network Termination 1) Access Server

Q3: What are the benefits of using a layered model?

Answer:

"Most communication environments separate the communication functions from application processing. This separation of networking functions is called layering."

Benefits

To divide the interrelated aspects of network operation into less complex elements.
To define standard interfaces for "plug-and-play" compatibility and multivendor integration.
To enable engineers to specialize design and development efforts on modular functions enabling new applications and services to be deployed without redesigning each lower layer.
To promote symmetry in the different internetwork modular functions so they interoperate.
To prevent changes in one area from effecting other areas so each area can evolve more quickly.
To divide the complexity of internetworking into discrete, more easily learned operations subsets.

Q4: Which OSI layer is responsible for physical addressing, media access and error reporting?

Answer:

The Data Link Layer (Layer # 2 in OSI model) is responsible for physical addressing, media access and error reporting.

Q5: Which OSI layer provides flow control and guaranteed end-to-end delivery of data?

Answer:

The Transport Layer (Layer # 4 in OSI model) is responsible for flow control and guaranteed end-to-end delivery of data.

Q6: At which OSI layer do most routing functions take place?

Answer:

The Network Layer (Layer # 3 in OSI model) is responsible for most of the routing functions.

Q7: What is meant by simplex, half-duplex and full-duplex communication?

Answer:

Simplex communication:
Date only travels in one direction between a sending and a receiving station.

Half-duplex communication:
Data can travel in either direction but not simultaneously. This means that while one station is sending data, other station must be in a listening or receiving mode.

Full-duplex communication:
Data can travel in either direction and simultaneously. This means that any station can send and receive the data at the same time.

Q8: At times a lower layer protocol combines data from many higher level processes on to a single connection. What is this called?

Answer:

It is called "Multiplexing".

Q9: What is the difference between the connectionless and connection oriented communication?

Answer:

Connection Oriented data handling involves using a specific path that is established for the duration of a connection. It involves three phases,

Establishment of Connection
Data Transfer
Termination of Connection

In connection Oriented data handling the

Connectionless data handling involves passing data through a virtual connection. Each message carries the full destination address and each one is routed through the system independent of all others. This service is modeled after the "Postal System". Normally, when two messages are sent to the same destination, the first one sent will be the first one to arrive. However, it is possible that the first one sent can be delayed so that the second one arrives first. With a Connection-Oriented service this is immposible.