Chapter 5Local Area Network

Concepts and Architecture

• Network Fundamentals

• Local Area Network (LAN)

• Open Systems Interconnection (OSI)

• LAN Architectures

Network Fundamentals

• Definitions

• Classifications

• Network topology

• Network types

• Local Area Network

Definition

• Network

• Backbond network

Classification

• Topology

• Ownership

• Geography

• Transmission

Network Topology

• Star

• Hierarchical

• Mesh

• Bus

• Ring

• Hybrid

Star Network

• Usage– Centralized processing or communication

• Pros– Expansion – Implementation– No limit to no. and length of arms

• Cons– Single point of failure– Overload of mater during peak traffic

Hierarchical Network

• Usage– Distributed processing

• Tree structure with a root

• pro– No single point of failure

Mesh Network

• Web structure

• Usage– Public telephone system

• Pro– Alternative communication route

• Con– Line cost

Bus Network

• Usage– Date entry or office environment

• Pros– Independent between nodes– High reliability

• Cons– Limited number of attached device– Hard to locate the problems

Ring Network

• Usage– Manufacturing

• Pros– Less attenuation– Error control– Network management

• Cons– Failing of a node

Hybrid Networks

• Usage– Connecting different networks

• Pro– Communication between networks

• Con– Conversion device and costs– Compatibility

Network Ownership

• Private networks

• Public networks

• Valued added networks

Private networks

• Full control

• Special needs

• Expense

Public networks

• Controlled by carriers

• Regulated by government

• Inexpensive

Valued Added Networks

• Functions– Code translation– Speed conversion– Store message and delivery

• Examples– Telex– SWIFT– SITA (airline)– IVAN (insurance)

Networks by Geography

• Wide area network (WAN)

• Metropolitan area network (MAN): 30 miles

• Local area network (LAN): 5 miles

LAN Characteristics

• Limited distance within a few miles

• High data rate - 2 to 1000Mbps

• Low error rate

• Good response time

• Private owned

• No regulation

• Share hardware, software, and data files

Business Needs

• Corporate asset for competitive edge

• Data accessibility (information distribution)

• Less expenses

• Better service - response time and reliability

• Higher productivity

• Control or secure

LAN Analysis & Design

• Meet business objectives (strategic planning)

• Prevent technological obsolescence

LAN Hardware & Software

• Hardware– PC: servers and clients– Network interface card (NIC): physical address– Media or Cables

• Unshielded twisted pair (inexpensive)

• Coaxial cable (faster, expensive)

• Optical fiber (fastest, expensive)

• Air for wireless

– Hub (compatible)• connect wires and cables, repeater, error detection

• Software: network operating system

Open System Interconnection Model

• International Standards Organization

• Interconnection of dissimilar network

• Seven Layers– Application– Presentation– Session – Transport– Network– Data Link– Physical

Application Layer

• Utilities support end-user application program

• Determine data to be send at originating end

• Process data at receiving end

Presentation Layer

• Change data format

• Compression/expansion

• Encryption/decryption

Session Layer

• Communication rules of machines or application programs

• Accounting functions

Transport Layer

• Identify receiving address

• Flow control: rate of transmission

• Recovery: calculate and check checksum of entire message

Network Layer

• Route message

• Dissemble and assemble data (packets)

• Accounting functions

Data Link Layer• By IEEE 802

• Establish link between two ends

• Detect and correct transmission error

• Add header and trailer

• Divide data unit for transmission (frames)

• Sublayers– Media access control (MAC): token ring or

Ethernet– Logical link control (LLC): assembling and

disassembling frames, error control, flow control

Physical Layer

• Electrical, mechanical, procedural specifications for data transmission

• Hardware specification by RS-232-C

Other Concepts

• Protocol

• Encapsulation/ de-encapsulation

Standards

• IEEE 802.2: LLC protocol

• IEEE 802.3: CSMA/CD baseband bus

• IEEE 802.4: token passing bus

• IEEE 802.5 token passing ring

• Fiber Distributed Data Interface (FDDI) Standard

LAN Architecture Model

• Network architecture includes– Access methodology– Logical topology– Physical topology

• Network configuration includes– Network architecture– Media choice

Access Methods• Contention: carrier sense multiple access

with collision detection (CSMA/CD)– Inexpensive NIC– For: office application– Not for: manufacturing due to inconsistent

response time

• Token passing: 24 bits of token (free or busy)– More efficient at higher network utilization rate– More expensive NIC– Supported by IBM

Topology

• Logical– Sequential– Broadcast

• Physical– Bus: line broken– Ring: PC or NIC broken– Star (hub, concentrator, MAU (multistation

access unit, repeater, switching hub): single point of failure

Ethernet

• Functionality– Access method: CSMA/CD

– Logical topology: broadcast

– Physical topology: bus or star

• Ethernet II– Header (preamble) for synchronizing

– Destination & source address (MAC layer address)

– Type field for network protocol

– Data field

– Frame check sequence (FCS): CRC-32 • IEEE 802.3 replace type field with length field

Media-related Ethernet• 10BaseT

• 10Base2 (Thinet with RG-58 coax)

• 10Base5 (thick coaxial cable RG-11)

• 100BaseT Fast Ethernet with 100-Mbps– 100BaseTX (2 pair of Category 5 UTP or 1 pair

of Type 1 STP)– 100BaseT4 (4 pair of Category 3, 4, or 5 UTP)– 100BaseFX (fiber optic cable)– Trade off between speed and maximum

network diameter

• Gigabit Ethernet (1000Base-X)

Token Ring• Functionality

– Access method: token passing

– Logical topology: sequence

– Physical topology: ring or star

• IEEE 802.5– Starting delimiter alert NIC about token approaching

– Access control field (1 for busy, 0 for free)

– Frame control field indicate regular data or network management frame

– Destination & source address (MAC layer address)

– Routing information field for multiple token ring LANs

– Data field

– Frame check sequence (FCS): CRC-32

– Ending delimiter (ending or intermediate frame)

– Frame status field for successful delivery

Fiber Distributed Data Interface

• Fiber distributed data interface (FDDI) by American National standard Institute (ANSI)

• Functionality– Access method: Modified token passing

– Logical topology: sequential

– Physical topology: dual counter-rotating rings

• Build-in reliability and longer distance• Single-attachment stations (SAS) or dual-

attachment stations (DAS)

Fiber Distributed Data Interface

• High speed backbone between LANs• Primary ring and secondary ring - 100Mbps token

ring• Fault tolerance• High-priority station having longer access time• Maximum 500 stations• Maximum length of 200 kilometers (rings)• Maximum 2 kilometers between stations

• Constant data rate for video and voice

Fiber Distributed Data Interface

• Applications– Campus backbone– High-bandwidth workgroups (multimedia

application)– High-bandwidth subworkgroup connection

(servers)• Hardware: FDDI concentrator or hub,

FDDI/Ethernet bridge• Media: fiber optic cable or copper distributed data

interface (CDDI) for limited distance (100m)

100VG-AnyLAN

• Ethernet and token ring packets

• Demand priority access (DPA) or demand priority protocol: round robin polling scheme

• Priority is assigned by application program and ports

• Max 4 hubs between two nodes

100VG-AnyLAN

• Hardware: 100VG-AnyLAN hubs arranged in a hierarchical form

• Media: 4 pair of Category 3, 4, or 5 UTP; 1 pair of Type 1 STP; or single mode and multimode fiber optic cable

Isochronous Ethernet

• Iso-Ethernet in IEEE802.9a (Isochronous Ethernet Integrated Services)

• Synchronize all circuits with a single common clocking reference

• Guaranteed delivery time for voice and video

• Use ISDN WAN link

Isochronous Ethernet

• 16.144-Mpbs bandwidth– P channel for Ethernet traffic– C channel ( B channel and D channel)

• Service Modes– 10BaseT– Mutiservice: multimedia– All-isochronous: real time video or voice

distribution

Isochronous Ethernet

• Hardware:– hubs: Iso-Ethernet attachment units (AU) – Workstation with Iso-Ethernet NIC: integrated

service terminal equipment (ISTE)

Wireless

• Transmitter and receiver

• 100 - 300 feet

• Infrared technology (line-of-sight)

• Spread spectrum technology (no ling-of-sight)

• Special application

Performance Factors

• Protocol (CSMA/CD, token ring)

• Speed of transmission (line)

• Amount of traffic

• Error rate

• Software

• Hardware

Selection Process

• Long range thinking, planning and forecasting

• Selection team

• Checklist of criteria

• Cost & benefit analysis

• Technical alternatives

• Management and Maintenance

Selection Criteria - I

• Number of user

• Geographic spread

• Applications

• Performance

• Cost

• Security

• Wiring

Selection Criteria - II

• Installation

• Maintenance

• Vendor support and training

• Future expansion

• Workstations

• Compatibility to existing LANs

• Interface to other networks

Costs• Workstations

• Servers

• Printers

• Cabling

• Bridges, routers, brouters, gateways

• Training

• People (consultant, administrator etc.)

• Maintenance

• Space & Environment

Installation• Choices

– Suppliers or dealers

– In house

• Tasks (project management)– Install hardware and software

– Test access and capability

– Trouble shoot

– Document

– Train user

– Help center

Management & Maintenance

• Organization: LAN administrator• Management: policies and procedures• Documentation• Hardware and software control• Change control• Back up (hardware and software)• Security (logical and physical)• Application (compatibility, integrity, & efficiency)• Performance monitoring

Security

• Password• Sign off• Encryption• Backup• Downloading• Viruses protection• Dial-up access• Legal software• Internal and external auditing• Written policy and procedure

Assignment

• Review chapter 5

• Read chapter 6