Miscellaneous Network Info• Brief history, WANs, LANs• Examples• Issues• Cabling

WAN – Wide Area Network

• Connect geographically separate networks

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

WAN

LAN

LAN

LAN

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.

A B

Digital linesAnalog lines

Modem

LANs were serial until 1984 or so.

Wiring was a big problem!

VAX

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

• There were many network protocols e.g. Appletalk, IPX, Decnet, OSI, SNA, IP

• Routers were needed to route each of these

• Now, it’s pretty much an IP world

Why doesn’t ATM play a role in the LAN?

• 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 BattlesIEEE 802.3 or ethernet (DEC, Xerox, Intel)

IEEE 802.4 token bus (General Motors)

IEEE 802.5 token ring (IBM)

Issues:Random access vs. deterministic approach

Installation

Hardware and cabling

Applications and protocols

Ethernet won• 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

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

Traffic Collapses to the Core

Example: Core is ATM (OC3)

Each floor in each building has a switch

…

To building floor

…

…

OC3

OC3 OC3

• Collapsed Backbone is where routing is

• Could build in redundancy by putting routers in buildings in case the backbone has a problem

Example: To the Buildings…

• 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…

Bridge

Now can do this…

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.

10BaseT – 10 Mbps

VLANsVirtual 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

• 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

• 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

• Hosted/Virtual PBX now available

• IP PBX now available

• Still need to connect to POTS (Plain Old Telephone System)

Voice Over 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

• QOS management needed

• QOS being built into router ports

• QOS can be built into switch ports

• Need to control applications

Example:Network Management

• Performance

• Fault

• Configuration

• Accounting

• Security:

Performance

– 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– 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

– 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

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

– Assigns privileges to user– No charge back

• Security– Firewalls– Monitoring

Some Link Layer Technologies

• 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

Protocol Cable Speed Topology

Ethernet twisted pair coaxial fiber

10Mbps Linear bus

star, tree

Fast Ethernet

twisted pair fiber

100Mbps star

LocalTalk twisted pair .23Mbps Linear bus, star

Token Ring Fiber 4 – 16 Mbps

Star-Wired Ring

FDDI Fiber 100 Mbps Dual ring

ATM twisted pair fiber

155 – 248Mbps

Linear bus, star, tree

Ethernet card with RJ-45, AUI, BNC connectors

Twisted Pair

Found in telephone applications, ethernet. Form of wiring in which two conductors are wound together to cancel out electromagnetic interferencefrom external sources and crosstalk for neighboring wires.

• 8 wires

• Shielded Twisted Pair used in areas susceptible to interference

• Unshielded Twisted Pair very common

UTP Categories

Type UseCategory 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)

• Ethernet 10BaseT 10Mbps• 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

Use Crossover to connect• 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

• PC to router

• PC to Hub/Switch

Coaxial Cable

• 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

• 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

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

AUI – Attachment Unit Interface

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

• 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

• 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

• 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)

Cisco also uses proprietary DB-60 connector. To connect in lab, use

DB-60 crossover cable

Typical T1 WAN connection

DSU/CSU – Data Server Unit/Channel Service Unit

Miscellaneous Technologies• ISDN Integrated Services Digital

Net (not telephone line)• 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

• OC768• 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