Networks and Protoco..

hardsweetlipsNetworking and Communications

Oct 28, 2013 (3 years and 7 months ago)

51 views

Networks and Protocols
CE00997
-
3

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 distance

Re
-
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


r
outer 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.

1

3

4

2

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:





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:





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: