Chapter 5 Local 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 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 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 –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 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 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