Network Devices

Lecture 1

Review Topologies

Physical Star Ring Dual Ring Bus Mesh

Logical Token Ring Bus

Media Twisted pair

UTP STP

Fiber RF Coax

10Base2 10Base5

NICs Identification – MAC address

MAC – media access control 48 bit/6 byte/12 hexidecimal unique

identifier First 6 hexidecimals identify the OUI –

organizationally unique identifier – identifies the manufacturer of the NIC card

Last 6 hexidecimals are the S/N of the device

Example: 00-E0-B8-57-3D-DC00-E0-B8OUI

57-3D-DCS/N

NIC Considerations Network compatibility (Ethernet or TR) Bus compatibility

PCI – peripheral component interconnect Newer computers or equipment 64-bit or 32-bit

ISA – industry std. architecture – old Older computers or equipment

Port compatibility Usu. Twisted pair; Multiple connector types is a combo card

H/W compatibility With O/S

Laptop NICs

PCMCIA - Personal Computer Memory Card International Association

Assuming this is a Ethernet/10BaseT network. How far apart can these computers be?

100 meters

Peer to Peer Network

A hub would regenerate the

signal.

Ethernet Network

Assume these computers are

in different offices. Some are more than

100 meters apart. How will they be able to communicate?

Hub Multiport repeater Regenerates signals Receives signal on one port; sends signal out all other

outgoing ports Extends the network because the signal has been

regenerated. Usu. two types of ports

MDI – medium dependent interface Uplink port

MDI-X – medium dependent interface crossed Regular port (already crossed) Use straight-through cable to connect computer to hub Use cross-over cable to connect from MDI-X port to MDI-X port

on a switch.

Ethernet Network

YTC1 has a message to go

to YTC3

YTC1 YTC2

YTC3YTC4

Only YTC3 would pick up the message.

Frame

Messages are broken into smaller pieces called frames for traversing the network.

HeaderAddress field

Source & Destination MAC

Data FCS Trailer

Bridge Network device that connects two

segments of a network or two LANs. Receives a “frame” on one port. If the

destination address on the frame is on another segment, it will forward the frame. Otherwise, it blocks the frame.

Reduces traffic; therefore, collisions. Builds MAC tables of the devices on the

segments connected to it. Largely replaced by Switches and

Routers.

80/20 Rule

80% of the traffic should not cross the bridge.

Only 20% of the traffic should be on the other side of the bridge.

Types of Bridges Transparent Bridges

Invisible to other devices on the network. Blocking and Fowarding Most popular type of bridge

Translational Bridges Connects two LANs running different protocols; for

instance, Ethernet and TR Translates the data from one protocol to the other.

Source-route Bridges Used in IBM Token Ring networks. Entire route from source to destination is embedded

within the frame.

Switch Intelligent network device Multiport bridge Looks at destination MAC address of

incoming frame and makes decision about whether to pick up the frame and if so, which port to forward the frame out.

Peforms microsegmentation Breaks up collision domains

Switch – cont’d Provides full-duplex operation

100 Mbps would be 200 Mbps operation in full duplex because you can send and receive simultaneously at 100 Mbps

Five processes Listening Learning Filtering Forwarding Blocking

Switching Methods Cut-through (FastForward)

Reads the destination address and forwards No error checking Fastest

Store and Forward Receives the entire frame before forwarding Performs basic error checking Most error free form of switching

Fragment-free After receiving first 64 bytes, forwards frame. A

collision fragment is less than 64 bytes.

Twisted Pair Cables

Straight-through cable Allows you to connect “unlike”

devices or “like” devices that have a port that has a crossed connection.

Cross-over cable Allows you to connect “like” devices.