CABLES and PROTOCOLS: SUGGESTED SOLUTIONS

1. Write short notes on different cable types that can be used for a network, with emphasis on the differences between each.

Coaxial Cable A single copper conductor at the center, with a braided metal shield separated by a plastic layer The metal shield insulates the cable from interference There are basically two types. Thin Coaxial or thinnet - 10Base2 in Ethernet networks maximum length 200m / 10 Mbps Thick Coaxial or thicknet - 10Base5 in Ethernet networks maximum length 500m / 10 Mbps Connectors used Most commonly used connector is call BNC connector. T-connector Barrel-connector Terminator Less susceptible to interference Needs to be terminated and either end
Unshielded Twisted Pair (UTP) Four twisted pairs of wires inside a plastic case Widely used and cheap. 10BaseT in Ethernet (10Mbps) Connectors used are named RJ-45 More susceptible for interference than co-axial cables.
Shielded Twisted Pair (STP) Extra shielding and hence less susceptible to interference and noise Bulkier than UTP because of the shielding and takes more space. More expensive. Mostly used in Token ring networks
Fiber Optic Consists of a center glass core surrounded by several layers of protective materials. Transmits light instead of electrical signals. 10BaseF in Ethernet Has the ability to transmit signals over much longer distances Uses ST (barrel shaped) and SC connectors (squared face) Immune to electro-magnetic interference. More expensive than other cable types. Difficult to connect Robust and takes less space.

2. List the different categories of cables that are specified (mainly for UTP cables), their data rates and uses.

These are specified by EIA/TIA 568B and ISO/IEC IS11801

Category	Speed	Uses
Category 1/2	upto 4Mbps	Suited mostly for voice - not use for data networking
Category 3	10 Mbps (can support 16 Mbps)	Mostly used for backbone cabling to support voice and low speed data communication.
Category 4	upto 16 Mbps	runs upto 100m but considered obsolete
Category 5	100 Mbps	operates at 100 MHz, for high speed networks
Category 5e	155 Mbps	Enhanced specification targeted to support Gigabit Ethernet
Category 6	1000 Mbps	operates at 250 MHz - for Gigabit Ethernet and ATM at extended distances
Category 7	upto 2.4 Gbps	operate at a maximum frequency of 600 MHz

3. Construct a wiring diagram for UTP cables that can be used to:

a) connect two dissimilar devices (eg a PC NIC and a hub) Use a Straight Through cable with Pin-to-Pin connections
b) connect two similar devices (eg a hub to a hub, or a PC NIC to another NIC) Use a CrossOver cable. Connect TD and RX pairs and preserve polarity

Click HERE for a completed Wiring Diagram
Click HERE for a more detailed discussion of UTP cables for Ethernet.

4. Write short notes on the following protocols (you may refer to your notes and the internet)...

Internet Protocol
Operates at the network layer in the OSI model / Internet layer in the TCP/IP protocol suite
Handles routing, fragmentation and reassembly
Identifies hosts using a 32 bit identifier (128 bit in IPv6)

Internet Protocol Exchange (IPX), implemented by Novell
Operates at the Network layer
Connectionless protocol that delivers packets across an internet
Provides NetWare workstations and file servers with addressing and internetworking routing services

NetBios Extended User Interface (NetBEUI)
Developed by IBM
Operates at the transport layer
Not routable so need to be used in conjunction with other protocols for a WAN or multi-LAN environments
Quick protocol with less overhead
First used in LAN Manager and later by network operating systems such as LAN Server, Windows for Workgroups, Windows 95 and Windows NT

LAN protocol
Widely used data communications network standard developed by DEC, Intel and Xerox.
Uses bus technology based on CSMA/CD access method
IEEE 802.3 standard
Operate at the Data Link layer
Addresses are 48 bit identifiers, generally called Ethernet or MAC address

LAN protocol originally developed by IBM
All hosts are connected in a ring and each host can directly hear transmissions only from it's immediate neighbor
Permission to transmit is granted by a token (message) that circulates along the ring
IEEE 802.5 standard
Data Link layer

A fast network technology transferring data in "cells" or fixed packet size
Constant cell size of 53 bytes
Creates virtual paths and virtual circuits which are identified by VPI / VCI pairs.
Assumes reliable transmission media

Netware Core Protocol (NCP)
Used by Novell networks
Operates at the presentation layer
Implemented as redirectors, which intercepts requests, formats them according to the protocol in use, and passes them to the lower level protocol
Primarily used for file and printer sharing with NFSP (Netware File Sharing Protocol)

Server Message Block
Microsoft presentation layer protocol similar to NCP with Novell
Used for sharing files, printers, serial ports and communications abstractions such as named pipes and mail slots between computers
Client-Server request response type protocol using TCP/IP
Many variants of the protocol has been developed, first variant known as the Core Protocol (a.k.a. PC Network Program 1.0)

Network Basic Input Output System (NetBIOS)
Provides a communication interface between the application program and the attached medium
Basically operate in the session layer
A NetBIOS session is a logical connection between any two names on the network
Works in conjunction with SMB
Identifies hosts and services with a name (NetBIOS name) in the form of "\\name"