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Brief history, WANs, LANs Examples Issues Cabling. Miscellaneous Network Info. WAN – Wide Area Network. Connect geographically separate networks ATM has played an important part in WAN (not LAN). LAN. LAN. WAN. LAN. LAN. WANs started with telephone (analog) lines.

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Miscellaneous network info

Brief history, WANs, LANs




Miscellaneous Network Info

Wan wide area network
WAN – Wide Area Network

  • Connect geographically separate networks

  • ATM has played an important part in WAN (not LAN)






WANs started with telephone (analog) lines.

Needed to send digital data over analog lines.

Wanted to use digital lines (e.g. FR, ATM) instead.



Analog lines

Digital lines


LANs were serial until 1984 or so.

Wiring was a big problem!

36/64/128 serial ports (local or dial)


Why doesn t atm play a role in the lan
Why doesn’t ATM play a role in the LAN? Decnet, OSI, SNA, IP

  • About 8 years ago ATM looked good, scalable (T1, T2, T3)

  • Every frame 53 byte cell size so HW could be simple

  • Had QOS feature built into the protocol

  • Current Ethernet switches would’ve been ATM switches

  • BUT Ethernet kept ramping up, had an installed base, and was simple

Lan technology battles
LAN Technology Battles Decnet, OSI, SNA, IP

IEEE 802.3 or ethernet (DEC, Xerox, Intel)

IEEE 802.4 token bus (General Motors)

IEEE 802.5 token ring (IBM)


Random access vs. deterministic approach


Hardware and cabling

Applications and protocols

Ethernet won
Ethernet won Decnet, OSI, SNA, IP

  • Many hadn’t thought it would scale, but it did.

  • To extend ethernet geographically, needed a bridge.

  • Spanning tree algorithm was major development.

Cabling system
Cabling System Decnet, OSI, SNA, IP

IBM started building structured cabling plants.

Devised a better copper cable so got reasonable distance for digital info.

CAT 5 was a major innovation - at every jack guaranteed to work to 300 ft (100 m).

Future is fiber optic (cost still high).

Example network with collapsed backbone
Example: Network with Collapsed Backbone Decnet, OSI, SNA, IP

Traffic Collapses to the Core


Core is ATM (OC3)

Each floor in each building has a switch

To building floor




Example to the buildings
Example: To the Buildings… Decnet, OSI, SNA, IP

  • Optical fiber runs from backbone router to building (in conduits)

  • Optical fiber runs between floors in building

  • Point of presence on each floor

  • From wiring closet on the floor, Category 5 (100Mbps) or Category 6 (1 Gbps), keep lengths to 50 m just to be safe

  • Ethernet used

Used to do this
Used to do this… Decnet, OSI, SNA, IP


Now can do this
Now can do this… Decnet, OSI, SNA, IP

10BaseT – 10 Mbps

Spanning tree is in silicon.

Every port has spanning tree running on it.

Others don’t see conversation between ports.

In switched ethernet, every port is its own ethernet.

VLANs Decnet, OSI, SNA, IP

Virtual LANs, VLANs, were important in switches

Not physically connected as a LAN.

HW can be programmed so each port belongs to a VLAN

(All belong to the same collision domain)

So all on VLAN see the ethernet packet.

Convergence Decnet, OSI, SNA, IP

  • Digitize all info & attach to a spigot so data, voice, video are carried together

  • Ethernet best effort service caused doubt 8 years or so ago

Private branch exchange
Private Branch Exchange Decnet, OSI, SNA, IP

  • Companies, enterprises use PBX for internal phone service

  • PBX is a circuit switch

  • Digital

  • Doesn’t go through telephone net

  • Phone line to PBX not very demanding (not like a data connection)

  • Highly reliable

Voice over ip
Voice Over IP Decnet, OSI, SNA, IP

  • Taking phones off PBX to do VoIP or using IP PBX

  • Some reliability issues in large environments

  • Over the WAN, it’s good & saves money for individuals

Quality of service
Quality of Service Decnet, OSI, SNA, IP

  • QOS management needed

  • QOS being built into router ports

  • QOS can be built into switch ports

  • Need to control applications

Example network management
Example:Network Management Decnet, OSI, SNA, IP

  • Performance

  • Fault

  • Configuration

  • Accounting

  • Security:

Performance Decnet, OSI, SNA, IP

  • Monitor activity of various types

  • Use traffic shaper that monitors application traffic and, when configured % exceeded, drops packets

  • Use Network Management platform to query nodes via SNMP and retrieve performance statistics

Fault Decnet, OSI, SNA, IP

  • Use SNMP to monitor switches, routers, servers to see if they’re up or down

  • Notify via paging, email if something is down

    (e.g. ISDN lines go down if no activity so may get errant message, then need to actively send traffic on line to check). Need to avoid storms.

  • Knocking off a cable or making a change is most likely reason for a node to be down. Sometimes it’s the path to the node that’s down.

  • Remote reboot.

  • Battery backups send low power traps.

Configuration Decnet, OSI, SNA, IP

  • Do some configuring using SNMP sets, but often configure first then deploy

  • Use Network Management platform to discover nodes in network to make sure nothing new is being attached or something isn’t being taken away

Accounting Decnet, OSI, SNA, IP

  • Network manager specifies user and device access to network resources.

  • Assigns privileges to user

  • No charge back

  • Security Decnet, OSI, SNA, IP

    • Firewalls

    • Monitoring

Some link layer technologies
Some Link Layer Technologies Decnet, OSI, SNA, IP

  • Ethernet – CSMA/CD, 10 – 1000 Mbps

  • Fast Ethernet – 100 Mbps, needs Cat 5

  • Gigabit Ethernet – 1Gbps

  • LocalTalk – Apple, CSMA/CA

  • Token Ring – IBM, decreasing use

  • FDDI – Fiber Distributed Data, WAN

  • ATM – Asynchronous Transfer Mode, WAN mostly

Twisted pair

Twisted Pair Decnet, OSI, SNA, IP

Found in telephone applications, ethernet. Form of wiring in which two

conductors are wound together to cancel out electromagnetic interference

from external sources and crosstalk for neighboring wires.

  • 8 wires Decnet, OSI, SNA, IP

  • Shielded Twisted Pair used in areas susceptible to interference

  • Unshielded Twisted Pair very common

Utp categories
UTP Categories Decnet, OSI, SNA, IP

Type Use

Category 1 Voice Only (Telephone Wire)

Category 2 Data to 4 Mbps (LocalTalk)

Category 3 Data to 10 Mbps (Ethernet)

Category 4 Data to 20 Mbps (16 Mbps

Token Ring)

Category 5 Data to 100 Mbps (Fast


  • Ethernet 10BaseT 10Mbps Decnet, OSI, SNA, IP

  • Ethernet 100BaseTX 100Mbps

  • Cables connecting NIC cards are now usually UTP with RJ-45 connectors

  • For 100BaseTX, the cable must satisfy Category 5 rating.

  • Cat 5 has 4 pairs of twisted wires. 10BaseT and 100BaseTX Ethernet use only 2 of the pairs

Twisted pair 2 flavors
Twisted Pair – 2 Flavors Decnet, OSI, SNA, IP

Use crossover to connect
Use Crossover to connect Decnet, OSI, SNA, IP

  • 2 PCs

  • 2 Routers

  • 2 Hubs/Switch

    Some hubs have an uplink port. Straight through can be used between uplink port of hub and regular hub port.

    If UTP port on switch is MDI/MDI-X (Medium Dependent Interface), either can be used to connect to another

Use straight through to connect
Use straight through to connect Decnet, OSI, SNA, IP

  • PC to router

  • PC to Hub/Switch

Coaxial cable
Coaxial Cable Decnet, OSI, SNA, IP

  • Single copper conductor with plastic insulation and braided metal shield

  • Difficult to install but greater cable lengths

  • Thick (10Base5) 500 meters

  • Thin (10Base2) 2 is for 200 but goes 185 meters

BNC is most common connector for coax. Used for video connections – analog and digital. Were commonly used on 10base2 ethernet networks.

Fiber optic
Fiber Optic connections – analog and digital. Were commonly used on 10base2 ethernet networks.

  • Glass core surrounded by protective materials (Ethernet is 10BaseF)

  • Transmits light vs. electronic signals so eliminates electrical interference

  • Longer distance than coax or twisted pair

  • Immune to moisture, lighting problem

  • Faster

  • Difficult to install

Fiber optic cable
Fiber Optic Cable connections – analog and digital. Were commonly used on 10base2 ethernet networks.

Uses standard connector (FC, SC, ST, LC, MTRJ)

Aui attachment unit interface
AUI – Attachment Unit Interface connections – analog and digital. Were commonly used on 10base2 ethernet networks.

A 15 pin physical connector interface between a NIC and an Ethernet cable

  • Some AUI/RJ-45 transceivers have AUI interface on one side and RJ-45 on the other

  • Becoming rarer because it’s common to include Medium Attachment Unit (ethernet transceiver) internally

Serial connections
Serial Connections connections – analog and digital. Were commonly used on 10base2 ethernet networks.

  • Majority use RS-232

  • RS-232 specifies 25-pin connector called DB-25. 25-pins not always needed so there are other connectors (DB-9, RJ-45)

Serial connection for router configuration
Serial Connection for Router Configuration connections – analog and digital. Were commonly used on 10base2 ethernet networks.

  • One use is to connect router to PC console port for configuration then use a terminal emulation program (e.g. kermit) to talk to the router

Serial wan connections
Serial Wan Connections connections – analog and digital. Were commonly used on 10base2 ethernet networks.

  • Router may have one or more serial WAN interfaces in addition to Ethernet interfaces.

  • Synchronous serial ports

  • Can operate in full-duplex modes

  • E.g. T1 line (1.544 Mbps)

  • Framing may be Point-to-Point Protocol or High Level Data Link (HDLC)

Typical t1 wan connection
Typical T1 WAN connection lab, use DB-60 crossover cable

DSU/CSU – Data Server Unit/Channel Service Unit

Miscellaneous technologies

ISDN Integrated Services Digital Net (not telephone line) lab, use DB-60 crossover cable

DSL Digital Subscriber Line (same cable as telephone)

T1 1.5 Mbps ~$800/month

T3 2nd fastest non-optical 45 Mbps ~15K/month

SONET Synchronous Optical Networking uses laser or light emitting diodes/LEDs to send digital info

OC3 155.52 Mbps Optical size of largest Internet backbone provider

OC12 fiber optic net 621.84 Mbps, smaller backbones

OC48 2488.32 Mbps/2.4 Gbps (48x basic SONET signal 51.84 Mbps)

OC192 as of 2005 only large ISPs 9953.28 Mbps


802.11b 11 Mbps

802.11g 54 Mbps

Cable 10 – 20 Mbps ~$100/month

Satellite slower than DSL or cable

Broadband intranet access > 56K dialup with cable modem and fiber optic

10 Gigabit ethernet

Miscellaneous Technologies