Topics
Network Topology
Cables and connectors
Network Devices
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Network Topologies
LANs and WANs - Geographical coverage
LANs
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A single geographical location, such as office building, school,
etc
Typically High speed and cheaper.
WANs
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Spans more than one geographical location often connecting
separated LANs
Slower
Costly hardware, routers, dedicated leased lines and
complicated implementation procedures.
Network Topologies
Topology - Physical and logical network layout
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Physical – actual layout of the computer cables and other
network devices
Logical – the way in which the network appears to the devices
that use it.
Common topologies:
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Bus, ring, star, mesh and wireless
Bus topology
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Uses a trunk or backbone to which all of the computers
on the network connect.
Systems connect to this backbone using T connectors or
taps.
Coaxial cablings ( 10Base-2, 10Base5) were popular
options years ago.
Bus Topology
Advantages
Disadvantages
Cheap and easy to implement
Network disruption when computers are
added or removed
Require less cable
A break in the cable will prevent all
systems from accessing the network.
Does not use any specialized network
equipment.
Difficult to troubleshoot.
5
Ring Topology
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Logical ring
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Meaning that data travels in circular fashion from one
computer to another on the network.
Typically FDDI, SONET or Token Ring technology are used
to implement a ring network
Ring networks are most commonly wired in a star
configuration
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Token Ring has multi-station access unit (MSAU),equivalent to
hub or switch. MSAU performs the token circulation internally.
Ring Topology
Advantages
Disadvantages
Cable faults are easily located, making
troubleshooting easier
Expansion to the network can cause
network disruption
Ring networks are moderately easy to
install
A single break in the cable can disrupt the
entire network.
7
Star Topology
All computers/devices connect to a central device called
hub or switch.
Each device requires a single cable
point-to-point connection between the device and hub.
Most widely implemented
Hub is the single point of failure
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Star Topology
Advantages
Disadvantages
Easily expanded without disruption
to the network
Requires more cable
Cable failure affects only a single
user
A central connecting device allows
for a single point of failure
Easy to troubleshoot and isolate
problems
More difficult to implement
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Mesh Topology
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Each computer connects to every other.
High level of redundancy.
Rarely used.
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Wiring is very complicated
Cabling cost is high
Troubleshooting a failed cable is tricky
A variation hybrid mesh – create point to point connection
between specific network devices, often seen in WAN
implementation.
Mesh Topology
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Advantages
Disadvantages
Provides redundant paths between
devices
Requires more cable than the other
LAN topologies
The network can be expanded
without disruption to current uses
Complicated implementation
Wireless networking
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Do not require physical cabling
Particularly useful for remote access for laptop users
Eliminate cable faults and cable breaks.
Signal interference and security issue.
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Wireless networking
Advantages
Disadvantages
Allows for wireless remote access
Potential security issues associated with
wireless transmissions
Network can be expanded without
disruption to current users
Limited speed in comparison to other
network topologies
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Cabling and Connectors
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General media considerations
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Broadband versus baseband
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Baseband transmissions use digital signaling and Time Division
Multiplexing (TDM)
Broadband transmissions use analog and Frequency Division
Multiplexing(FDM)
Dialog modes: Simplex, half duplex and full duplex
Cabling and Connectors
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Media interference
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Electromagnetic interference (EMI) and cross talk
Network media vary in their resistance to the effect of EMC.
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Attenuation
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Resistance :Coaxial cable > UTP, STP > UTP, Fiber > all
Maximum distance
Repeaters
Attenuation-related problems require a network analyzer to detect
Bandwidth
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UTP is susceptible and fiber is resistant
Transmission capacity of a media
Data throughput is measured in bits per second(bps), Mbps, and Gbps
For today’s application-intensive networks, Old 10Mbps is not enough,
100Mbps is very common and 1000Mbps is used too.
Network Media
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Cable-based media
 Coaxial
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Twisted pair
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Copper wire to conduct the signals electronically
Was the choice for LAN for many years.
Retiring
Copper wire to conduct too
Most widely used
Fiber-optic
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transmits the signals as light
Uses glass or plastic conductor and
High Cost. Restricted to where segment length and higher speeds
are needed.
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Server room, backbone
Twisted-pair cabling
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Has been around for a long time
Created for voice transmissions
Most widely used media for networking
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Lighter
More flexible
Easier to install
Cheaper
Greater speeds
Two types:
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Unshielded twisted pair (UTP)
Shielded twisted pair (STP)
Twisted-pair cabling
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UTP is more commonplace
STP
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provides the extra shielding by using an insulating material
wrapped around the wire
Greater resistance to EMI and attenuation
More cost
Five main categories
Category Cable Types
Application
1
UTP
Analog voice
2
UTP
Digital voice, 1Mbps data
3
UTP, STP
16Mbps data
4
UTP, STP
20Mbps data
5, 5e
UTP, STP
Data, 100Mbps, 1G
6, 6e
UTP, STP
Data, 1G, 10G
RJ-45 connectors
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RJ-45 are used with twisted-pair cabling.
Resemble ordinary phone jacks (RJ-11)
Eight wires instead of four
Larger.
Check out this page for how to make cat5 cable.
http://www.tomax7.com/aplus/cat5.htm
Fiber-optic cable
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Use light transmissions
EMI, crosstalk and attenuation become no issue.
Well suited for data, video and voice transmissions
Most secure of all cable media
Installation and maintenance procedures require
skills
Cost of cable
Cost of retrofitting of existing network equipment
because incompatible with most electronic
network equipment
Fiber-optic cable
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Single mode fiber:
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A single direct bean of light, allowing for greater distances and increased
transfer speeds.
Multimode fiber:
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Many beams of light travel through the cable
This strategy weakens the signal, reducing the length and speed the data
signal can travel.
Fiber-optic connectors
There are a variety of connectors and several ways of
Connecting these connectors, such bayonet, snap-lock,
and push-pull connectors. A couple here:
FC
MIC, Standard FDDI
connector
ST
LC
SC duplex
SC
Wireless media
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Three types:
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Radio wave
Infrared
Microwave
Speeds of wireless solutions don’t keep pace with
cable solutions
Installation and maintenance are far more
complicated and costly.
Some solutions require line-of-sight, such as infrared
and microwave.
IEEE 802.3 standards
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IEEE 802.3 standards defines a range of networking
systems that are bases on the original Ethernet
standard.
Standard
Cable type
Segment
Length
Connector
Topology
10Base2
Thin Coaxial
185 meters
BNC
Physical bus
10Base5
Thick
Coaxial
500 meters
Vampire Taps Physical bus
10BaseT
Category
3,4,5 twisted
pair
100 meters
RJ-45
Physical star
Fast Ethernet IEEE 802.3u
Standard
Cable Type
Segment
Length
Conn Topology
ector
100BaseTx Category 5 UTP
100 meters
RJ-45 Physical star
100BaseT4 Category 3,4,5 UTP
100 meters
RJ-45 Physical star
100BaseF
X
412/Multimode
fiber-optic
10,000/singlemode fiberoptic
SC,S
T,MI
C
Multimode/Single-mode
fiber-optic cable
Physical star
Gigabit Ethernet
802.3z and 802.3ab
Standard
Cable Type
Segment length
Connector
1000BaseLX
Multimode/ singlemode fiber
550/multimode
5000/single-mode
Fiber connectors
1000BaseSX
Multimode fiber
550 meters using 50
Micron multimode
fiber
Fiber connectors
1000BaseCX
STP twisted pair
25 meters
9-pin shielded
connector, 8-pin fiber
channel type 2
connector
1000BaseT
Category 5 UTP
100 meters
RJ-45
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Check out this page for how to make cat5 cable.
http://www.tomax7.com/aplus/cat5.htm
Color codes
Pin Number Designations
There are pin number designations for each color in T568B
The pin designations are as follows:
Color Codes for T568B
Pin color
pair
name
--- ---------------1
wh/or
2
TxData +
2
or
2
TxData –
3
wh/grn
3
RecvData+
4
blu
1
5
wh/blu
1
6
grn
3
RecvData7
wh/brn
4
8
brn
4
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The pinouts for a crossover cable
Straight-through
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Crossover cable
Networking Devices
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•
repeaters
Hubs
Switches
Bridges
Routes
Gateways
Network Interface Cards (NICs)
Wireless access points
Modems
Punch_down panels
Hubs
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The bottom of the networking food chain
Connect device and create larger networks
Small hubs 5-8 ports (workgroup hubs)
Some hubs have more ports, up to 32 normally
Direct data packets to all devices connected to the
hub - shared bandwidth
animation
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Scalability, Collision, inefficient
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Bridges
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Divide larger networks into smaller sections
Check MAC address, forward or block the data
Learning bridge builds list of MAC address by watching the
traffic on the network.
Two issues to consider:
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Placement 80/20 rule
Bridging loops
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IEEE 802.1d Spanning tree protocol
Types of bridges
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Transparent bridge
Source route bridge
Translational bridge
Bridges
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Source Route Bridge
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Used in Token Ring networks.
. (ring number and bridge
The entire path
number) is embedded within Packet
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Translational bridge
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Used to convert one networking data
format to another.
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Search frame
Route discovery frame
For example, from Token Ring to Ethernet
and vice versa.
Switches
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Like hub, connectivity points of Ethernet network
Forward only to the port that connects to the
destination device
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knows MAC address
Match the MAC address in the data it receives.
Fully switched network, a dedicated segment for each
device is connected to switch. Expensive.
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Switches
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Allow full duplex Ethernet
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Nodes only communicate with switch, never directly to each
other
Use twisted pair or fiber optic cabling, using separate
conductors for sending and receiving data.
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collision pair is used to transmit data
It was half duplex before – one device can transmit at one given time,
double the capacity, 100Mbps become 200Mbps
Most LAN are mixed with hubs and switches.
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37
http://www.cisco.com/warp/public/473/lan-switch-cisco.shtml
Switch routing method
Packet-based switches use one of the following method
to route packet.
 Cut-through
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Forward as soon as it received the destination MAC – first
14 bytes
Can cause propagation of error
Store-and-forward
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Error checked before being forwarded
Errors are not propagated through network
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Bad frames are discarded
Error checking takes time.
Considerably slower
Switch Routing Method
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FragmentFree
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Take the advantage of both.
Check errors by reading the first 64byte of packets where
collision most likely happens
Offer near cut-through switching performance
Switch physical design
LAN switches vary in their physical design
 Shared-memory
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Matrix
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Internal grid with input port and output crossing each other
First check MAC, then switch makes a connection where two
ports (input/output) intersect
Bus-architecture
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Common buffer for all ports
Common-bus
Dedicated buffer for each port and a circuit to control the
bus access
Switch and Transparent Bridging
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Most LAN switches use transparent bridging to create
address lookup tables
Transparent bridging is a technology that allows a
switch to learn everything it needs to know about the
location of nodes on the network within the network
administrator having to do anything. Has five parts:
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Learning
Flooding
Filtering
Forwarding
Aging
http://computer.howstuffworks.com/lab-switch10.htm
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http://www.cisco.com/warp/public/473/lan-switch-transparent.swf
http://www.cisco.com/warp/public/473/lan-switch-cisco.shtml
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Hub and switch cabling
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To create larger networks, connect hubs and switches
using
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Standard port - Medium Dependent Interface-Crossed
(MDI-X)
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To see each other as an extension, no signal to be crossed
Using crossover cable between two MDI-X ports
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Two wires are crossed internally
Medium Dependent Interface (MDI)
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Standard port with special cable
Special ports with a standard cable
To uncross the internal crossing
Punch_down panels
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Wiring closets
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45
http://www.youtube.com/wa
tch?v=3wdDRtGLiow
Labeling schemes
Routers
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Create larger networks by joining two networks
segments.
Dedicated hardware device or computer systems
with more than one network interface and routing
software.
Routing table
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Static routing
Dynamic routing
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Use special routing protocols to pass info to other routers.
Distance Vector Routing (RIP)
Link state routing (OSPF)
Switch and Router
• Different with router
– Typically switch works on lower level (Data
link Layer) while Router works in higher level
(Network Layer)
– Algorithms for router and switch about how to
forward packers are different
• For example, switch will forward broadcast, so does
hub, not router- the address has to be specific.
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Routers and Layer 3 Switch
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While most switches operate at the Data link layer(layer2),
some incorporate features of a router and operate at the
network layer (layer3).
Layer 3 switches are faster because they are build on
“switching” hardware
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a router is needed for VLANS communication
Why not build a router in the switch itself and do the forwarding in
hardware
EX: IP forwarding – all in hardware
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Route lookup
Decrement the Time to Live (TTL)
Recalculation the checksum
Forward the frame the frame to correct output port
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Gateways
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Any device that translate one data format to another is
called a gateway.
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Router
Bridge
Software
Gateway and default gateway
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CSU/DSU
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Channel Server Unit/Digital Service Unit ( CSU/DSU) or
Data Service Unit
Convert digital format on LAN into signal used on WAN
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Sit between LAN and access point provided by telecom
company
Many routers have CSU/DSU functionality
Wireless access points
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Devices that provide connectivity between wireless LAN
devices and in most cases a wired network.
Antennae
Convert signal from radio wave or other to that used on
the LANs.
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Modems
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Modulator/Demodulator, convert digital signal
generated by computer into analog signals that can
travel over conventional phone line.
Connect to ISP
Dialing up to a LAN
Internal add-in expansion cards or external devices
connect to serial or USB port
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PCMCIA cards for laptop
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Modem itself
Speed of the Universal Asynchronous Receiver/Transmitter
(UART) chip,
Speed
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UART 16950 has the speed of 921,600kbp
Network cards
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Called Network Interface Cards (NIC)
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Attached to external port
PC card
Internal Network card
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System bus compatibility
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System Resources – device conflict
Media compatibility
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Peripheral Component Interconnect (PCI)
Industry Standard Architecture (ISA)
Twisted pair, coaxial or fiber-optic connection?
Driver
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ISDN adapters
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Integrated Services Digital Networking (ISDN) is a
remote access and WAN technology that can be used
in place of a Plain old telephone systems dial-up link
Greater speeds than modem, pick up and drop the
line considerable faster.
Require ISDN terminal adapter
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Although digital signal, different format with the those used
on LAN.
Create multiple communication channels on a single line.
System area network cards
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Connecting computer systems in a cluster
High-performance unit.
Device
Hub
Function/Purpose
Connects devices on a
twisted-pair network.
Connects devices on a
twisted-pair network.
Key Points
A hub does not perform any tasks besides signal
regeneration.
A switch forwards data to its destination by using the MAC
address embedded in each packet.
Bridge
Divides networks to reduce
overall network traffic.
A bridge allows or prevents data from passing through it by
reading the MAC address.
Router
Connects networks together. A router uses the software-configured network address to
make forwarding decisions.
Gateway
Translates from one data
format to another.
CSU/DSU
Translates digital signals usedCSU/DSU functionality is sometimes incorporated into other
on a LAN to those used on a devices, such as a router with a WAN connection.
WAN.
Enables systems to connect Network interfaces can be add-in expansion cards,
to the network.
PCMCIA cards, or built-in interfaces.
Switch
Network card
ISDN terminal
adapter
Connects devices to ISDN
lines.
System area network Used in server clusters to
card
provide connectivity between
nodes.
WAP
Provides network capabilities
to wireless network devices.
Modem
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Provides serial
communication capabilities
across phone lines.
Gateways can be hardware or software based. Any device
that translates data formats is called a gateway.
ISDN is a digital WAN technology often used in place of
slower modem links. ISDN terminal adapters are required to
reformat the data format for transmission on ISDN links.
System area network cards are high-performance devices
capable of coping with the demands of clustering
applications.
A WAP is often used to connect to a wired network, thereby
acting as a link between wired and wireless portions of the
network.
Modems modulate the digital signal into analog at the
sending end and perform the reverse function at the
receiving end.
MAC addresses
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Unique 6-byte address burned info network interface,
expressed in hexadecimal
No matter which protocol is used, MAC address is
the means by which the network interface is
identified on the network.
IEEE managing MAC address assignment
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IEEE has a system Identifying the manufacturer by looking at
the MAC address
Discover MAC address, depend on the OS
Ifconfig /all on WINDOWs NT/2000
Ifconfig –a on Linux/UNIX
58
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Watch the Intel Gigabit demo.
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http://www.intel.com/network/connectivity/resources/demos/gi
gabit/base.swf
IEEE and Networking standards
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Institute of Electrical and Electronic Engineers (IEEE)
developed a series of networking standards
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Networking technologies developed by manufacturers are
Compatible
Cabling, networking devices and protocols are all
interchangeable under the banner of a specific IEEE
Specification Name
802.1
Internetworking
802.2
The LLC(Logincal Link Control) sublayer
802.3
CSMA/CD ( Carrier Sense Multiple Access with Collision
Detection) for Ethernet networks
802.4
A token passing bus
802.5
Token Ring networks
802.6
Metropolitan Area Network (MAN)
802.7
Broadband Technical Advisory Group
802.8
Fiber-Optic Technical Advisory Group
802.9
Integrated Voice and Data Networks
802.10
Standards for Interoperable LAN/MAN Security (SILS) (Network
Security)
802.11
Wireless networks
802.12
100Mbps technologies, including 100BASEVG-AnyLAN
61
802.3 IEEE standard
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Defines characteristics for Ethernet networks.
New additions, 802.3u for Fast Ethernet, 802.3z for
Gigabit Ethernet, referred to as 802.3x.
Speed: Original 10Mbps, Fast Ethernet 100Mbps,
Gigabit Ethernet 1000Mbps
Topology: bus or star.
Media: Coaxial and twisted pair cabling, also fiber
optic cable.
Access method: CSMA/CD
62
802.5 IEEE standard
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Specifies the characteristics for Token Ring Networks.
Introduced by IBM in the mid 80s, network topology
of choice until the rise of the popularity of Ethernet.
Speed: 4 to 16Mbps
Topology: logical ring and most often a physical star.
Logical ring is often created in the Multistation Access
Unit (MSAU)
Media: twisted pair cabling.
Access method: token passing.
63
802.11b IEEE Standard
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64
Specifies the characteristics of wireless LAN Ethernet
networks.
Special devices called wireless access points to allow
communicate.
Also connect to wired networks to create wireless
portions of entire networks.
Speed: 802.11b specifies 11M. Today 802.11g can be
108Mbps
Media: 802.11b standard is 2.4G radio waves.
Topology: physical wireless, logical bus
Access method: Carrier Sense Multiple Access/Collision
Avoidance (CSMA/CA ), a variation of CSMA/CD.
FDDI
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Fiber Distributed Data Interface (FDDI) standard was
developed by American National Standards Institute
(ANSI)
Dual ring technology for fault tolerance
Speed: 100Mbps or higher
Topology: dual ring topology
Media: fiber optic cable, > 2 kilometers. Also possible
use copper wire as Copper Distributed Data
Interface (CDDI).
Access method: token-passing access method
65
Standard
Speed
802.3
10Mbps
Physical
Topology
Logical
Topology
Media
Access
Method
Bus and Star
Coaxial and
Twisted pair
CSMA/CD
(802.3u)
100Mbps( Fast
Ethernet)
Star
Bus
Twisted pair
CSMA/CD
(802.3z)
1000Mbps
Star
Bus
Twisted pair
CSMA/CD
802.5
4Mbps and
16Mbps
Star
Ring
Twisted pair
Token
passing
802.11b
11Mbps
Wireless
Bus
Radio waves
CSMA/CA
FDDI
100Mbps
Dual Ring
Ring
Fiber-optic
Twisted
pair/CDDI
Token
passing
66