Page 82 - DCAP406_DCAP_207_Computer Networks

Unit 5: Networking Devices

Hubs are used to interconnect various incoming connections with different outgoing Notes
connections at the Physical layer of the OSI model.

Router are used to connect two devices at the network layer of the OSI Model. Routers are
used to connect both similar and dissimilar LANs and operates layer 3. Router protocols
consist of both bridging and routing protocols like inter-router, serial line protocols and
protocol stack routing and bridging protocols.
Gateways are used to connect totally dissimilar networks because they can perform protocol
conversion for all seven layers of the OSI Model. Gateway routers are used to connect
dissimilar LANs and perform all of the functions of bridges and routers. It operates at all
seven layers of the OSI Reference Model. A switching hub can operate with multiple
media (coaxial cable, UTP, and fiber).

There are a number of ways to perform switching such as circuit Switching, Packet
Switching, Message Switching and Cell Switching.

5.8 Keywords

Bridges: It is used to connect similar LANs together and operates at the bottom two layers of the
OSI model. It uses MAC addresses (physical addresses) are used to determine whether data is
necessary to transmit to other segments or not.

Encapsulating Bridge: Dissimilar LANs such as Ethernet-to-token ring can be connected with
the help of bridge.
Gateways: Gateway routers are used to connect dissimilar LANs and perform all of the functions
of bridges and routers. It operates at all seven layers of the OSI Reference Model.
Inter-router Protocols: These are router-to-router protocols that can operate over dissimilar
networks. This protocol routes information and stores data packets during periods of idleness.

Media Access Control (MAC) Bridge: This is used to connect dissimilar LANs such as Ethernet-to-
token ring using encapsulation or translation.
Protocol Stack Routing and Bridging Protocols: This advises the router as to which packets
should be routed and which should be bridged.
Repeaters: It amplifies the signal, which has got attenuated during the course of transmission
because of the physical conditions imposed by the transmission media.
Routers: Routers are used to connect both similar and dissimilar LAN and operates on the
network layer of OSI model using the physical layer, data link layer and network layer to
provide connectivity, addressing and switching.
Serial Line Protocols: This protocol is widely used over serial or dialup links connecting unlike
routers.
Spanning Tree Protocol (STP) bridge: This is also known as adaptive or self-learning bridges and
is defined in IEEE 802.1 standards.

Switching Hubs: A switch, which resembles a hub, is known as switching hub.

5.9 Review Questions

1. What is the main purpose of using router in a network?
2. Why does hub fall under the category of bus topology while physically it comes under
star topology type?

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