Understanding Network Devices and Internetworking

1. Computer Networks

2. Internetworking Devices • Network Interface Card (NIC) • Repeaters • HUB • Bridge • Switch • Router

3. NIC • Usually PCI Card • Plugs into Motherboard • Separately designed for Ethernet, Token Ring, FDDI etc • Communicate with network through Serial Connection • Communicate with System with Parallel Connection • Have embedded MAC/Physical Address on a chip

4. NIC Functionality • Performs most of Layer Two functions • LLC (Logical Link Control) • Interface with upper layers • MAC (Medium Access Control) • Shared access to medium • Framing • Packages Frames • Signaling • Create Bits/Signals for transmission over Medium • Error Detection • New NICs have built-in Error Detection Facility

5. Repeaters • It boosts the signal so that it could travel a longer cable length • Works at layer One (Physical Layer) • Advantage • Extend cable length • Disadvantage • Also propagate the noise

6. HUB • Connects multiple nodes in a single network segment • Works at Layer One (Physical Layer) • Broadcasting Device • Multi-port Repeater • Detects and troubleshoots collisions • Became Obsolete

7. Bridge • Used for Network Segmentation at Layer two • Segmentation • Dividing a big network into parts • Advantage • Less Collisions • More Bandwidth • Makes MAC table • Intelligence Device (Make Decisions)

8. Switch • Similar to HUB but is an intelligent device • Forwards Packets based upon their destination address • Increase bandwidth • A switch gives any device on the network the full bandwidth instead of sharing the available bandwidth. • Intelligence ensures only destination receives the data, at maximum bandwidth. • Decrease collisions • Direct Connection between multiple hosts

9. Switch • Also known as Multi-port Bridge • Store & Forward Device • Store & Forward Vs Cut through • MAC Table • Typically works on Layer 2 • Layer 3 Switches are also available • Advance Switches are manageable • MAC Filtering • SNMP (Simple Network Management Protocol) • VLAN Setting

10. Router • A router is a device that forwards data packets from one network to another. • Routers read the network address in order to route data via the optimum path. • Data packets which are addressed to a device at the same site of the router will not be let through. • Convert data structure from one media to another, for example Ethernet <=> ISDN. • Routers can interconnect all networks in the enterprise. • For example two different networks like a LAN and the Internet

11. Router • Also Performs Segmentation • Layer 3 Segmentation based upon IP (logical address) • Performs switching as switch • Best Path Selection based upon Network address • Encapsulation/De-encapsulation of Packet • Routing Table

12. Gateway • Some times router may be used as a Gateway • Gateway is an essential functionality provided by router • It is a node that serve as entrance to another network and vice versa • Normally used between private networks and internet • Any packet whose address doesn’t belong to current network is forwarded to gateway • Gateway may/may not perform NAT