Networks and Protocols CE Week 2a

Network hardware

Unicast, Broadcast, Multicast Unicast – the packets are sent to a specific host, only that host can receive the packets Broadcast – packets are sent out to all active devices, e.g. dhcp request, ARP request etc… Multicast – essentially the same as a broadcast but to a select number of hosts that are multicast aware/enabled

Repeater Accepts 1 incoming set of data, re-times and amplifies the signal then pass it on to overcome physical limitations of cable e.g. UTP = max 100m REPEATER Original waveform Waveform over distanceRe-timed waveform

Hubs Non-active network device Do not make decisions Re-time and amplify the signal Can be thought of as a multi-port repeater HUB Waveform over distance Re-timed waveform Original waveform

Hubs Allow the connection of a number of devices together, IF on the SAME logical network Creates 1 broadcast and 1 collision domain Hub - interconnects two or more workstations into a local area network When workstation transmits to a hub – Hub immediately resends data frame out to all connecting links, considered a broadcast device Hub can be managed or unmanaged – Managed hub possesses enough processing power that it can be managed from a remote location

Routers Perform layer 3 switching known as routing Most commonly based on IP address Use ROUTING protocols to route ROUTED protocols Routing protocols: RIP, IGRP…. The protocol that decides how to get there Routed protocols: TCP/IP, IPX/SPX… The protocol that carries the data

Routers Router - device that connects a LAN to a WAN or a WAN to a WAN Router: 1.Accepts outgoing packet 2.Removes any LAN headers and trailers 3.Encapsulates necessary WAN headers and trailers Because router has to make wide area network routing decisions  router has to dig down into the network layer of the packet to retrieve network destination address

Routers Routers are often called “layer 3 devices” – Operate at the third layer, or OSI network layer, of the packet Make decisions based on IP address (most common) as to what is the best route to take Each port is a collision domain (bandwidth shared between devices connected to the hub) Normally a hub or switch is connected to a router Often incorporate firewall functions

Routers

Cisco 2600 series routers

Routers Route A Route B Route C

Bridges A bridge (or bridge-like device) Can be used to connect two similar LANs, such as two CSMA/CD LANs Can also be used to connect two closely similar LANs, such as a CSMA/CD LAN and a token ring LAN Examines destination address in a frame Either forwards this frame onto next LAN or does not Examines source address in frame Places this address in a routing table to be used for future routing decisions

Bridges

Switches A layer 2 device, can be thought of as a multi- port bridge Makes decisions as to which is the based route based on MAC address Each port is its own collision domain 100% of bandwidth per port Each port is its own collision domain

Switches Combination of hub and bridge Can interconnect two or more workstations Like bridge, it observes traffic flow and learns When a frame arrives at a switch, the switch Examines destination address Stores the source address Forwards frame out the one necessary connection Workstations that connect to Hub  on shared segment Switch  on switched segment

Switches Backplane of a switch is fast enough to support multiple data transfers at one time A switch that employs cut-through architecture is passing on the frame before the entire frame has arrived at the switch Multiple workstations connected to a switch use dedicated segments – Very efficient way to isolate heavy users from the network A switch can allow simultaneous access to multiple servers, or multiple simultaneous connections to a single server

The switch

Switch cont

Switches

Isolating Traffic Patterns and Providing Multiple Access

Isolating Traffic Patterns and Providing Multiple Access

Isolating Traffic Patterns and Providing Multiple Access

Full-Duplex Switches Allows for simultaneous transmission and reception of data to and from a workstation This full duplex connection helps eliminate collisions To support a full duplex connection to a switch, at least two pairs of wires are necessary One for the receive operation One for the transmit operation Most people install four pairs today, so wiring is not problem

Full-Duplex Switches

Cisco 2950 series

Hannah’s LAN Internetworking in Action A small office with 20 workstations in one room and 15 workstations in another room were connected to a server via 100BaseTX One hub is in a closet near the 20 workstations while a second hub is near the server

LAN Internetworking in Action:

Now Hannah’s wants to connect their LAN to the Internet A router is added next to the server and connected to the hub The router is connected to a high-speed telephone line such as a T-1 service The router will need to be programmed to perform IP addressing and firewall functions

LAN Internetworking in Action:

Now network usage is so high that Hannah’s must consider segmenting the network Hannah’s decides to install a database server near the original server and replace both hubs with switches

LAN Internetworking in Action: