Transcript Local Area Networks

Wrapping The Package
Devices & Data Encapsulation
Evolution of LAN Devices
NICs, Repeaters, & Hubs
Bridges
Switches
Routers
NIC Specifics
NICs provide hosts with access to
media by using a MAC address.
MAC stands for Media Access Control
NICs operate at Layer 2 !!
NICs, Repeaters, & Hubs
The First LAN
NIC
NIC
To connect two computers, you must...
Install a NIC card in each.
Attach computers NIC
using a crossover cable
You made a crossover cable in Ch. 5
NICs, Repeaters, & Hubs
Repeaters can be used
to increase the distance
NIC
NIC
So what
can
we
use
if
this
distance
Repeaters
amplify
and
What’s the maximum
100ismeters
or
approx.
300 feet
greater
than
100 meters?
retime
signals
distance for Cat 5 cable?
NICs, Repeaters, & Hubs
NIC
NIC
Using repeaters was fine as long as a business
only needed two computers networked.
NIC
What if a business wanted a
third computer attached?
Or a fourth? What
device would they need?
NIC
NICs, Repeaters, & Hubs
A multi-port repeater!
Also called a...
NIC
NIC
Hub
NIC
NIC
A Dilemma!
As businesses expanded their
networks, they began to
cascade hubs.
NIC
NIC
NIC
NIC
What’s The Problem?
1) Hubs share bandwidth between all
attached devices.
2) Hubs are stupid, Layer 1 devices.
They cannot filter traffic.
3) Most LANs use a “broadcast topology,”
so every device sees every packet
sent down the media.
Let’s take a look at how broadcasting works
Broadcasts
In this picture, all hubs forward
all traffic to all devices.
Broadcasts
So, if Host 1 sends a packet to Host
2, all hosts see the packet. This is
what we mean by a broadcast
topology
1
2
The red arrows show that all hosts receive the
ping request. Only Host 2 will respond.
What’s The Solution?
We need a smarter hub!
What’s a “smarter hub” called?
A Bridge!
Bridges filter network traffic based on
MAC addresses.
Let’s take a look at how this works.
Bridge
To lessen the amount of LAN traffic,
businesses began to use bridges to
filter frames based on MAC addresses.
Bridge
1
2
Now, if Host 1 sends a packet to 2,
only the hosts on that LAN segment
see the packet.
Bridges--Summary



More intelligent than hubs—that is, they
can analyze incoming frames and forward
(or drop) them based on addressing
information.
They create more collision domains,
allowing more than one device to transmit
simultaneously without causing a collision.
They maintain address tables.
Switch
A switch (also know as a multi-port
bridge), can effectively replace these
four bridges.
Switch
Another benefit of a switch is that each
LAN segment gets dedicated bandwidth.
10 Mbps
10 Mbps
The Cloud
10 Mbps
10 Mbps
10 Mbps
Switch
1
2
a switch
is astop
multi-port
ButSince
a switch
cannot
an ARPbridge,
request
we knowfrom
it will
stop local
Traffic
from
broadcast
traveling
to all
other
LAN
traveling to other network segments.
segments.
Switch
For example, Host 1 ARP Host 16. Since the
MAC address
is unknown
to the
the
What device
will solve
this switch,
problem?
switch will flood the ping request out all ports.
1
16
Router
Routers filter traffic based on IP addresses.
The IP address tells the router which LAN
segment the packet belongs to.
1
16
Devices Function At Layers
Know These!
Devices Function At Layers
Also know that each
device not only works at
its layer, but all layers
below it.
Devices Function At Layers
For example, a router is
a layer 3 device but also
uses MAC addresses
(layer 2) and repeats
the signal (layer 1)
Devices Function At Layers
One last bit of information from Chapter 3
At what layers do
ALL 7two
LAYERS!!
these
operate?
The Cloud
Chapter 3
Labs
3.4.2