of 57 /57
LAN/WAN Interconnectivity Chapter 2

LAN/WAN Interconnectivity

Embed Size (px)

Citation preview

Page 1: LAN/WAN Interconnectivity

LAN/WAN Interconnectivity

Chapter 2

Page 2: LAN/WAN Interconnectivity

Learning ObjectivesExplain the OSI reference model, which sets standards for LAN and WAN communicationsDiscuss communication between OSI stacks when two computers are linked through a networkApply the OSI model to realistic networking situations

continued…

Page 3: LAN/WAN Interconnectivity

Learning ObjectivesDescribe the types of networks as represented through LAN topologies

Describe major LAN transmission methods, including Ethernet, token ring, and FDDI

Explain basic WAN network communications topologies and transmission methods, including telecommunications, cable TV, and satellite technologies

Page 4: LAN/WAN Interconnectivity

LAN/WAN InterconnectivityIntense competition between three sectors:

Telecommunications companies

Cable TV companies

Satellite communications companies

Page 5: LAN/WAN Interconnectivity

OSI Reference ModelFoundation that brings continuity to LAN and WAN communicationsProduct of two standards organizations:

ISOANSI

Developed in 1974Set of communication guidelines for hardware and software design

Page 6: LAN/WAN Interconnectivity

OSI Guidelines Specify…How network devices contact each other; how devices using different protocols communicate

How a network device knows when to transmit and not transmit data

How physical network network devices are arranged and connected

continued…

Page 7: LAN/WAN Interconnectivity

OSI Guidelines Specify…Methods to ensure that network transmissions are received correctly

How network devices maintain a consistent rate of data flow

How electronic data is represented on network media

Page 8: LAN/WAN Interconnectivity

OSI Layers

Page 9: LAN/WAN Interconnectivity

OSI LayersBottom layers

Support for physical connectivity, frame formation, encoding, and signal transmission

Middle layersEstablish and maintain a communication session between two network nodesMonitor for error conditions

Uppermost layersApplication/software support for encrypting data and assuring interpretation/presentation of data

Page 10: LAN/WAN Interconnectivity

Physical Layer FunctionsProvides transfer medium (eg, cable)

Translates data into a transmission signal

Sends signal along the transfer medium

Includes physical layout of network

Monitors for transmission errors

Determines voltage levels for data signal transmissions and to synchronize transmissions

Determines signal type (eg, digital or analog)

Page 11: LAN/WAN Interconnectivity

Analog Signals

Page 12: LAN/WAN Interconnectivity

Digital Signals

Page 13: LAN/WAN Interconnectivity

Data Link Layer FunctionsConstructs data framesCreates CRC information; checks for errorsRetransmits data if there is an errorInitiates communications link; makes sure it is not interrupted (ensures node-to-node physical reliability)Examines device addressesAcknowledges receipt of a frame

Page 14: LAN/WAN Interconnectivity

Data Link LayerData link frame contains fields consisting of address and control information

Two important sublayersLogical link control (LLC)

Media access control (MAC)

Connectionless service versus connection-oriented service

Page 15: LAN/WAN Interconnectivity

Network Layer FunctionsDetermines network path for routing packetsHelps reduce network congestionEstablishes virtual circuitsRoutes packets to other networks, resequencing packet transmissions when neededTranslates between protocols

Page 16: LAN/WAN Interconnectivity

Transport Layer FunctionsEnsures reliability of packet transmissions

Ensures data is sent and received in the same order

Sends acknowledgement when packet is received

Monitors for packet transmission errors and resends bad packets

Breaks large data units into smaller ones and reconstructs them at the receiving end for networks using different protocols

Page 17: LAN/WAN Interconnectivity

Session Layer FunctionsEstablishes and maintains communications link

Determines which node transmits at any point in time

Disconnects when communication session is over

Translates node addresses

Page 18: LAN/WAN Interconnectivity

Presentation Layer FunctionsTranslates data to a format the receiving node understands (eg, from EBCDIC to ASCII)

Performs data encryption

Performs data compression

Page 19: LAN/WAN Interconnectivity

Application Layer FunctionsEnables sharing remote drivers and printers

Handles e-mail messages

Provides file transfer services

Provides file management services

Provides terminal emulation services

Page 20: LAN/WAN Interconnectivity

Communicating Between Stacks

OSI model provides standards for:Communicating on a LAN

Communicating between LANs

Internetworking between LANs and WANs and between WANs and WANs

Page 21: LAN/WAN Interconnectivity
Page 22: LAN/WAN Interconnectivity

Peer Protocols

Page 23: LAN/WAN Interconnectivity

Primitives

Page 24: LAN/WAN Interconnectivity

Layered Communications

Page 25: LAN/WAN Interconnectivity

Applying the OSI Model

Page 26: LAN/WAN Interconnectivity

Types of NetworksThree main topologies

Bus

Ring

Star

Page 27: LAN/WAN Interconnectivity

Bus TopologyBuilt by running cable from one PC or file server to the next

Terminators signal the physical end to the segment

Page 28: LAN/WAN Interconnectivity

Advantages of Bus TopologyWorks well for small networks

Relatively inexpensive to implement

Easy to add to it

Page 29: LAN/WAN Interconnectivity

Disadvantages ofBus Topology

Management costs can be high

Potential for congestion with network traffic

Page 30: LAN/WAN Interconnectivity

Ring TopologyContinuous path for data with no logical beginning or ending point, and thus no terminators

Page 31: LAN/WAN Interconnectivity

Advantages of Ring TopologyEasier to manage; easier to locate a defective node or cable problem

Well-suited for transmitting signals over long distances on a LAN

Handles high-volume network traffic

Enables reliable communication

Page 32: LAN/WAN Interconnectivity

Disadvantages ofRing Topology

Expensive

Requires more cable and network equipment at the start

Not used as widely as bus topologyFewer equipment options

Fewer options for expansion to high-speed communication

Page 33: LAN/WAN Interconnectivity

Star TopologyOldest and most common network design

Multiple nodes attached to a central hub

Page 34: LAN/WAN Interconnectivity

Advantages of Star TopologyGood option for modern networks

Low startup costs

Easy to manage

Offers opportunities for expansion

Most popular topology in use; wide variety of equipment available

Page 35: LAN/WAN Interconnectivity

Disadvantages ofStar Topology

Hub is a single point of failure

Requires more cable than the bus

Page 36: LAN/WAN Interconnectivity

Bus Networks in a Physical Star Layout

No exposed terminators

Capability for connecting multiple hubs to expand network in many directions

Expansion opportunities for implementing high-speed networking

Popular design; wide range of equipment available

Page 37: LAN/WAN Interconnectivity

LAN Transmission MethodsEthernet

IEEE 802.3 specificationsBroadest options for expansion and high-speed networking

Token ringIEEE 802.5 specifications

FDDI (Fiber Distributed Data Interface)High-speed variation of token ring

Page 38: LAN/WAN Interconnectivity

EthernetUses CSMA/CD access method for data transmission on a network

Typically implemented in a bus or bus-star topology

Carrier sense

Collision

Page 39: LAN/WAN Interconnectivity

Ethernet Communications

Page 40: LAN/WAN Interconnectivity

Ethernet II

Page 41: LAN/WAN Interconnectivity

Ethernet Standards

Page 42: LAN/WAN Interconnectivity

Token RingDeveloped by IBM in the 1970s; remains a primary LAN technology

Employs physical star topology with logic of ring topology

Each node connects to a central hub, but the frame travels from node to node as though there were no starting or ending point

Page 43: LAN/WAN Interconnectivity

Token Ring Frame

Page 44: LAN/WAN Interconnectivity

Token Ring TermsMultistation access unit (MAU)

Beaconing

Broadcast storms

Page 45: LAN/WAN Interconnectivity

FDDIFiber-optic data transport method capable of a 100-Mbps transfer rate using a dual ring topology

Synchronous versus asynchronous communications

Nodes monitor network for error conditionsLong periods of no activity

Long periods where the token is not present

Class A and Class B nodes

Page 46: LAN/WAN Interconnectivity

WAN Network Communications

Typical providers of WAN network servicesTelecommunications companiesCable TV companiesSatellite providers

Newer sources of WAN connectivityCable television networksSatellite TV companiesWireless WANs

Wide use of star topology

Page 47: LAN/WAN Interconnectivity

Telecommunications WANsEarliest source of WAN connectivityRegional telephone companies, also called:

TelcosRegional bell operating companies (RBOCs)

Long-distance telecommunications companiesPlain old telephone service (POTS) or public switched telephone network (PSTN)

Page 48: LAN/WAN Interconnectivity

General Topology Linking LATA and IXC Lines

Page 49: LAN/WAN Interconnectivity

Connecting LANs througha T-Carrier Line

Page 50: LAN/WAN Interconnectivity

T-Carrier Services and Data Rates

Page 51: LAN/WAN Interconnectivity

Cable TV WANsAlso called cablecos or multiple system operators (MSOs)

Use a distributed architecture that consists of several star-shaped centralized locations

Headend is the main focal point in the star

Page 52: LAN/WAN Interconnectivity
Page 53: LAN/WAN Interconnectivity

Wireless WANsUse radio, microware, and satellite communications

Packet radio communications

Page 54: LAN/WAN Interconnectivity

Topology of a Radio Wave WAN Joining Two LANs

Page 55: LAN/WAN Interconnectivity

WAN Transmission MethodsUse different switching techniques to create data paths (channels) for transmitting data

SwitchingEnables multiple nodes to simultaneously transmit and receive data, or

Enables data to be transmitted over different routes to achieve maximum efficiency in terms of speed and cost

Page 56: LAN/WAN Interconnectivity

Switching TechniquesTime division multiple access (TDMA)

Divides channels into distinct time slots

Frequency division multiple access (FDMA)

Divides channels into frequencies

Statistical multiple access Dynamically allocates bandwidth based on application need

Circuit switching Uses a dedicated physical circuit

Message switching Uses store-and-forward method of data transmission

Packet switching Combines circuit and message switching

Page 57: LAN/WAN Interconnectivity

Chapter SummaryOpen Systems Interconnection (OSI) model

Basic network topologies

Key LAN transmission methods

WAN communications options

WAN transmission methods