Nt1310 Unit 6

11.1 What is network topology?

“Network topology is the arrangement of the various network elements such as node, link, of computer network. Basically, it is topological structure of a network which ether be physically or logically.”

11.4 Why are there multiple LAN standards?

There multiple LAN standards because there might be wide range of data rate and transmission that might need to support. For that reason there are a set of standard that are developed by IEEE 802 committee which are accepted and used by most of the product in the market today. Some may use the standard for Token ring, Ethernet and Wireless.

11.8 What functions are performed by a bridge?

“A bridge is a device that is used for the interconnection of LANs that use identical

protocols for the physical and link layers. The use of a bridge increases reliability (break network into self-contained units), performance, security and geographic distance. The functions of the bridge are rather much simple. Individually frame is transported by copying it from one LAN and repeated with the same bit pattern to the other, it contains buffer space adequate to handle peak needs, the bridge must contain routing and addressing information and it may handle more than two LANs.”
11.8 What is spanning tree?

“The Spanning Tree Protocol (STP) is an older network protocol that ensures a loop-free topology for any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them.”

What is the difference between a hub and a layer 2 switch?

A Hub is a networking device that allows one to connect multiple PCs to a single network. Hubs may be based on Ethernet, Firewire, or USB connections. “A switch is a control unit that turns the flow of electricity on or off in a circuit. It may also be used to route information patterns in streaming electronic data sent over networks. “

11.11 What is difference between a store-and-forward switch a cut-through switch?

The difference between a store-forward switch and a cut-through switch is that store-and-forward accepts a frame on an input line buffer it for a little while then send it to its appropriate output line; cut-through switch and the other hand takes the advantage that destination address appears at the beginning of the MAC frame. In a cut-through switch environment, the layer 2 switch begin to repeat incoming frame onto the appropriate output line as soon as it recognize the destination

address.
Problems
11.3a A circuit-switched, star-topology local network. Call setup time is negligible and the data rate on the medium is 64kbps. Time=number of bits/Data Rate= (8*106)/(64*103)=125 second or 2hours and 5seconds.

11.6a two LANs are connected via two bridges that are connected by a point-to-point link.

User T1 t9 User
LLC

T2
X25-3 X25-3

t8 LLC
MAC
MAC X25-2 MAC X25-2 MAC
Physical T3 T4 PHY PHY T5 PHY PHY T6

T7 Physical

(a) Architecture
t1, t9 User Data

t1, t8 LLC-H User Data

t3, t4, t6, t7 MAC-H LLC-H User Data MAC-T

t5 Link-H MAC-H LLC-H User Data Link-T

11.9 A station on a LAN includes an attached bridge sends out a frame to a device that is not present on any of the segments of the total network. What does the bridge do with this frame?
Bridge makes no modification to the content or format of the frames it receives nor does it encapsulating them with additional header. Each frame to be transferred is simple copy from the LAN and repeat exactly the same bit pattern on the on the other LAN.