Metropolitan and Wide Area Networks

Metropolitan and Wide Area Networks PowerPoint PPT Presentation

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Definitions. MAN - metropolitan area network - a network spanning a geographical area that usually encompasses a city or county area. It interconnects various building or other facilities within this citywide area. MANs typically span from 3 to 30 miles and connect backbone networks and LANs, providing dial-in and dial-out capability to LANs, BN, mainframes, and access to the Internet..

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Metropolitan and Wide Area Networks

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1. Metropolitan and Wide Area Networks After studying this Chapter you should: understand the circuit-switched services and architectures understand the dedicated-circuit services and architectures understand the packet-switched services and architectures understand VPN services and architectures indicate how to improve MAN and WAN performance

2. Definitions MAN - metropolitan area network - a network spanning a geographical area that usually encompasses a city or county area. It interconnects various building or other facilities within this citywide area. MANs typically span from 3 to 30 miles and connect backbone networks and LANs, providing dial-in and dial-out capability to LANs, BN, mainframes, and access to the Internet.

3. Definitions WAN - wide area network - a network spanning a large geographical area, often hundreds or thousands of miles. Its nodes can span cities, states, or national boundaries. This network interconnects computers, LANs, BNs, MANs, and other data transmission facilities on a countrywide or worldwide basis.

4. US Communications Common carriers - government-regulated private companies that sell or lease communication services and facilities to the public. profit-oriented primary products are communication circuits for voice, data, and image transmissions local exchange carrier (LEC) - local service interexchange carrier (IXC) - long distance service

5. Regulating Agencies Tariff - the schedule of rates (prices) and description of services to be received when a particular type of communication service is purchased or leased. Federal Communications Commission (FCC) regulates interstate and international communications in the U.S. Canadian Radio-Television and Telecommunications Commission (CRTC) Public Utilities Commission (PUC) regulates intrastate communications

6. Circuit-Switched Networks Basic Architecture cloud architecture lease connection points in the network dial-up the connection to establish a temporary circuit flexible connection must be made to transfer data data can only be transferred to receiving computer move the burden of network design and management to the vendor

7. Circuit-Switched Architecture

8. Circuit-Switched Services public switched telephone network (PSTN) Plain Old Telephone Service (POTS) Integrated Services Digital Network (ISDN) Broadband Integrated Services Digital Network (BISDN)

9. POTS Plain Old Telephone Service common dial-up services requires a modem most common form of at home Internet connection normal voice telephone network different circuit path each call charges based on miles/minutes (same as voice) AT&T Wide Area Telephone Service (WATS) direct dial bulk rate service for both voice and data 800 and 888 area codes

10. ISDN Integrated Services Digital Network (ISDN) combines voice, video, and data over the same digital circuit lease connection points must have special equipment ISDN network terminator (acts like a hub) NIC (called a terminal adapter; TA) ISDN modem (no always required) need a service profile identifier (SPID) ISDN chip for communication boards (at Carriers end office)

11. ISDN basic rate interface (BRI) 3 Channels 2-64 Kbps transmission channels (B-channels) 1-16 Kbps control signaling channel (D-channel) primary rate interface (PRI) 24 Channels 23-64 Kbps transmission channels 1-16 Kbps control signaling channel Europe standard is 30B + 1D

12. B-ISDN Broadband ISDN (B-ISDN) second generation ISDN uses ATM to move data great potential for high speed networking full duplex channel at 155.2 Mbps full duplex channel at 622.08 Mbps asymmetrical service with two simplex channels upstream at 155.2 Mbps downstream at 622.08 Mbps

13. Advantages and Disadvantages of Circuit-Switched Services Advantages: simple flexible inexpensive with low usage Disadvantages: inconsistent quality low data transmission

14. Dedicated Circuit Networks Basic Architecture Private circuit services (dedicated or leased lines) point-to-point circuits leased for a fixed fee available for the exclusive use of the customer available 7/24 customer specifies end points and carrier installs them connected with multiplexers or channel service unit/data service unit (CSU/DSU)

15. Dedicated Circuit Architecture

16. Ring-Based WAN Design connects all computers in a closed loop usually a series of point-to-point dedicated circuits (T1) messages pass in both directions full duplex direction selected based on shortest path Disadvantages: time delay traffic delay delays in one circuit, affects the entire network

17. Ring-Based WAN Topology

18. Star-Based WAN Design connects all computers to one central computer that routes messages usually a via a series of point-to-point dedicated circuits (T1) easy to manage faster than ring topology failure on one circuit does not affect other areas Disadvantages: very susceptible to traffic problems central computer must have capacity to handle peaks in network traffic

19. Star-Based WAN Design

20. Mesh-Based WAN Design full or partial mesh every computer is connected to every other computer often by point-to-point dedicated circuits combine benefits from ring and star topologies Disadvantages: uses decentralized routing (each computer performs its own routing) more processing time wasted network capacity

21. Mesh-Based WAN Design

22. Dedicated Circuit Service Voice Grade Circuits T-carrier circuits SONET circuits

23. Voice Grade Circuits Voice Grade Equivalent Channels - analog voice communication or data transmission dedicated to the organization conditioning to improve quality of data transmissions

24. T-Carrier Services T-1 Circuits (DS1) synchronous data rate of 1.544Mbps transmission speeds from 56 Kbps to 1.544 Mbps digitized voice using PCM 64 Kbps time division multiplexing 24 simultaneous voice channels CSU/DSU units Fractional T-1(DS0) portions of the T-1 circuit is leased at lower costs can lease up to 64Kbps of the circuit

25. T Carrier System Hierarchy T-Carrier Designation DS Designation Speed

26. SONET Synchronous Optical Network (SONET) std for optical transmissions at gigabits per second synchronous digital hierarchy (SDH) requires CSU/DSU each level above the OC-1 is created by IMUX

27. SONET SONET Designation SDH Designation Speed

28. Packet-Switched Networks Basic Architecture services that interconnect many cities user buys a connection into the carriers cloud store and forward data transmission uses packet assembly and disassembly (PAD) devices at both ends splits transmissions into packets messages from different destinations are interleaved for transmission

29. Packet-Switched Networks

30. Packet-Switched Networks Packetizing splitting messages into individual packets instantaneous and continuous In connectionless service, PAD breaks up the message into packets, adds a destination address and sequence number to each packet, and transmits the packet In connection-oriented service, PAD establishes virtual transmission circuits, assembles/disassembles the packet, and transmits the packet in what appears to be a dedicated point-to-point circuit

31. Packet Transmission interleaved packets short bursts of data with spaces between maximizes use of the network routing datagram - connectionless service adds a destination and a sequence number switched virtual circuit - connection-oriented virtual end-to-end circuit established all packets take the same route

32. Packet Transmission

33. Virtual Circuits Two types of virtual circuits are available from the carriers permanent virtual circuits (PVCs) committed information rate (CIR) maximum allowable rate (MAR) switched virtual circuits (SVCs) both are established using software

34. Packet-Switching Protocols There are five protocols in use for packet switched services: X.25 Asynchronous Transfer Mode (ATM) Frame Relay Switched Multimegabit Data Service (SMDS) Ethernet/IP packet networks

35. X.25 oldest packet switched service standard developed by ITU-T services offered datagram switched virtual circuit permanent virtual circuit services replaces the LAN protocols: LAP-B at the data link layer PLP at the network layer sometimes called reliable packet service

36. Asynchronous Transfer Mode packet-switched data no error control on message discards bad packets uses forward error control on the header only data is encapsulated into fixed length packets of 53 bytes QoS information set transmission priorities negotiate data transmission rates ATM is scaleable

37. X.25 and ATM Switching

38. Frame Relay data link layer protocol that transmits data faster than X.25 but slower than ATM encapsulates packets variable length packets up to 8K bytes negotiates transmission speed CIR MAR frame relay assembly and disassembly (FRADs) minimal error control, discards packets with errors no guaranteed QoS

39. SMDS Switched Multimegabit Data Service (SMDS) offered by most Bell and IXC companies not yet standardized switched version of the T-carrier and SONET services main advantage is switching but does not provide any advantages over frame relay reduces the number of T-1 lines needed

40. Ethernet/IP Packet Networks Ethernet/IP services for the WAN does not require translation or encapsulation provided over private fiber optic network bypasses common carrier networks CIR speeds from 1 Mbps to 1 Gbps approximately 1/4 the cost of more traditional services all traffic entering the packet network must be Ethernet using IP

41. Virtual Private Networks Basic Architecture lease an Internet connection to the ISP from the common carrier any access rate any access technology requires VPN devices VPN device encapsulates the outgoing packet with a protocol used to move it through a tunnel layer-2 VPN layer-3 VPN

43. Advantages: low cost flexibility Disadvantages: traffic on the Internet is unpredictable several competing standards vendor equipment and services not compatible Advantages and Disadvantages of Virtual Private Networks

44. Intranet VPN provides virtual circuits between organization offices over the Internet Extranet VPN also connects partners, customer and suppliers Access VPN employees to access the organization's networks from a remote location Types of VPNs

45. MAN/WAN Performance Performance Checklist Increase Computer and Device Performance upgrade devices change routing protocol (either static or dynamic) Increase Circuit Capacity analyze message traffic and upgrade to faster circuits where needed check error rates Reduce Network Demand change user behavior analyze network needs of all new systems move data closer to users

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