Topics

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Network Topology Cables and connectors Network Devices

Network Topologies

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LANs and WANs - Geographical coverage LANs

A single geographical location, such as office building, school, etc

Typically High speed and cheaper. WANs

Spans more than one geographical location often connecting separated LANs

Slower Costly hardware, routers, dedicated leased lines

and complicated implementation procedures.

Network Topologies

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Topology - Physical and logical network layout 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:

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

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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.

Ring Topology

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Logical ring 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 Token Ring has multi-station access unit

(MSAU),equivalent to hub or switch. MSAU performs the token circulation internally.

Ring Topology

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Advantages DisadvantagesCable 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.

Star Topology

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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

Star Topology

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Advantages DisadvantagesEasily 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

Mesh Topology

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Each computer connects to every other. High level of redundancy. Rarely used.

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.

Wireless networking

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Advantages DisadvantagesAllows 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

Cabling and Connectors General media considerations

Broadband versus baseband 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 Electromagnetic interference (EMI) and cross talk Network media vary in their resistance to the effect of EMC.

UTP is susceptible and fiber is resistant Attenuation

Resistance :Coaxial cable > UTP, STP > UTP, Fiber > all Maximum distance Repeaters Attenuation-related problems require a network analyzer to

detect Bandwidth

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 Cable-based media

Coaxial Copper wire to conduct the signals electronically Was the choice for LAN for many years. Retiring

Twisted pair Copper wire to conduct too Most widely used

Fiber-optic transmits the signals as light Uses glass or plastic conductor and High Cost. Restricted to where segment length and

higher speeds are needed. Server room, backbone

Twisted-pair cabling Has been around for a long time Created for voice transmissions Most widely used media for networking

Lighter More flexible Easier to install Cheaper Greater speeds

Two types: Unshielded twisted pair (UTP) Shielded twisted pair (STP)

Twisted-pair cabling UTP is more commonplace STP

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 Application1 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

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

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 Single mode fiber:

A single direct bean of light, allowing for greater distances and increased transfer speeds.

Multimode fiber: 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

MIC, Standard FDDI connector

FC

LC

There are a variety of connectors and several ways of Connecting these connectors, such bayonet, snap-lock, and push-pull connectors. A couple here:

SC duplex

ST

SC

Wireless media Three types:

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 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

Connector

Topology

100BaseTx Category 5 UTP 100 meters RJ-45 Physical star

100BaseT4 Category 3,4,5 UTP 100 meters RJ-45 Physical star

100BaseFX

Multimode/Single-mode fiber-optic cable

412/Multimode fiber-optic 10,000/single-mode fiber-optic

SC,ST,MIC

Physical star

Gigabit Ethernet 802.3z and 802.3ab

Standard Cable Type Segment length Connector

1000BaseLX Multimode/ single-mode 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

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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   RecvData- 7       wh/brn  4 8       brn     4

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The pinouts for a crossover cable

Straight-through Crossover cable

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Networking Devices

• 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 bandwidthanimation

Scalability, Collision, inefficient

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:

Placement 80/20 rule Bridging loops

IEEE 802.1d Spanning tree protocol Types of bridges

Transparent bridge Source route bridge Translational bridge

Bridges

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Source Route Bridge Used in Token Ring networks. The entire path (ring number and

bridge number) is embedded within Packet Search frame Route discovery frame

Translational bridge Used to convert one networking

data format to another. For example, from Token Ring to

Ethernet and vice versa.

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Switches

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Like hub, connectivity points of Ethernet network

Forward only to the port that connects to the destination device 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.

Switches

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Allow full duplex Ethernet 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. 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.

37http://www.cisco.com/warp/public/473/lan-switch-cisco.shtml

Switch routing method

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Packet-based switches use one of the following method to route packet.

Cut-through Forward as soon as it received the destination

MAC – first 14 bytes Can cause propagation of error

Store-and-forward Error checked before being forwarded Errors are not propagated through network

Bad frames are discarded Error checking takes time. Considerably slower

Switch Routing Method

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FragmentFree 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

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LAN switches vary in their physical design Shared-memory

Common buffer for all ports Matrix

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 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: Learning Flooding Filtering Forwarding Aging

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http://computer.howstuffworks.com/lab-switch10.htm

http://www.cisco.com/warp/public/473/lan-switch-transparent.swf

43http://www.cisco.com/warp/public/473/lan-switch-cisco.shtml

Hub and switch cabling

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To create larger networks, connect hubs and switches using Standard port with special cable Special ports with a standard cable

Standard port - Medium Dependent Interface-Crossed (MDI-X) Two wires are crossed internally

Medium Dependent Interface (MDI) To see each other as an extension, no signal to be

crossed Using crossover cable between two MDI-X

ports To uncross the internal crossing

Punch_down panels

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Wiring closets http://

www.youtube.com/watch?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 Static routing Dynamic routing

Use special routing protocols to pass info to other routers.

Distance Vector Routing (RIP) Link state routing (OSPF)

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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.

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 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

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. Router Bridge Software

Gateway and default gateway

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 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.

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 PCMCIA cards for laptop

Speed Modem itself Speed of the Universal Asynchronous

Receiver/Transmitter (UART) chip, UART 16950 has the speed of 921,600kbp

Network cards

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Called Network Interface Cards (NIC) Attached to external port PC card Internal Network card

System bus compatibility Peripheral Component Interconnect (PCI) Industry Standard Architecture (ISA)

System Resources – device conflict Media compatibility

Twisted pair, coaxial or fiber-optic connection? Driver

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 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.

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Device Function/Purpose Key PointsHub Connects devices on a

twisted-pair network.A hub does not perform any tasks besides signal regeneration.

Switch Connects devices on a twisted-pair network.

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.

Gateways can be hardware or software based. Any device that translates data formats is called a gateway.

CSU/DSU Translates digital signals used on a LAN to those used on a WAN.

CSU/DSU functionality is sometimes incorporated into other devices, such as a router with a WAN connection.

Network card Enables systems to connect to the network.

Network interfaces can be add-in expansion cards, PCMCIA cards, or built-in interfaces.

ISDN terminal adapter

Connects devices to ISDN lines.

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 card

Used in server clusters to provide connectivity between nodes.

System area network cards are high-performance devices capable of coping with the demands of clustering applications.

WAP Provides network capabilities to wireless network devices.

A WAP is often used to connect to a wired network, thereby acting as a link between wired and wireless portions of the network.

Modem Provides serial communication capabilities across phone lines.

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 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/2000Ifconfig –a on Linux/UNIX

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Watch the Intel Gigabit demo. http://www.intel.com/network/connectivity/resourc

es/demos/gigabit/base.swf

IEEE and Networking standards

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Institute of Electrical and Electronic Engineers (IEEE) developed a series of networking standards Networking technologies developed by

manufacturers are Compatible Cabling, networking devices and protocols are all

interchangeable under the banner of a specific IEEE

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Specification Name802.1 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

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

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.

802.11b IEEE Standard

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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

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Standard Speed Physical Topology

Logical Topology

Media Access Method

802.3 10Mbps 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