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WAN’s and Routers

WAN’s and Routers. PJC CCNA Semester 2 Ver. 3.0 by William Kelly. Wan Characteristics. WAN’s cover a wide geographical area (1000 m is usually the cut-off point between a LAN and a WAN) They involve a service contract with a carrier WAN’s usually use serial connections (Why serial?).

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WAN’s and Routers

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  1. WAN’s and Routers PJC CCNA Semester 2 Ver. 3.0 by William Kelly

  2. Wan Characteristics • WAN’s cover a wide geographical area (1000 m is usually the cut-off point between a LAN and a WAN) • They involve a service contract with a carrier • WAN’s usually use serial connections (Why serial?)

  3. WAN Performance Characteristics • Uptime – be careful about the timeframe used to state uptime (it may differ from your clients needs) • Mean Time between Failure (MTBF) • Ambient temperature • Power Supply characteristics (filtered?) • Quality and handling of the devices • Uptime Monitors • Netsaint, and MRTG (UNIX/WIN versions)

  4. WAN Performance Characteristics • Traffic Volumes - • Maximum –The peak volume you expect your network to handle • Average – Traffic you can expect in a typical business day • Delay • Propagation Delay • Satellite uplink/downlink Delay • Forwarding Delay

  5. WAN Devices • Routers - offer many services, including LAN and WAN interface ports.  • Switches - connect to WAN bandwidth for voice, data, and video communication. • Modems - interface voice-grade services. Modems include CSUs/ DSUs and TA/NT1 devices that interface ISDN services. • Communications Servers - concentrate dial-in and dial-out user communication

  6. WAN Standards • EIA/TIA-232: developed by TIA/EIA, supports signal speeds of up to 64kbps, formerly called RS-232 • EIA/TIA-449: a faster version of EIA/TIA-232 (up to 2 Mbps), capable of longer cable runs. • EIA/TIA-612/613: A standard describing HSSI, which provides access to services at T3 (45 Mbps), E3 (34 Mbps), SONET (51.84 Mbps) rates. • V.35 : An ITU-T standard describing a synchronous, physical-layer protocol used for communications between a network access device and a packet network. For speeds up to 48kbps • X.21 -- An ITU-T standard for serial communications over synchronous digital lines. • G.703 - Connections between telephone company equipment and DTE using British Naval connectors (BNCs) Operating at E1 data rates. • EIA-530 - Two electrical implementations of EIA/TIA-449: RS-422 (for balanced transmission) and RS-423 (for unbalanced transmission).

  7. WAN Standards • High-Level Data Link Control (HDLC) • A proprietary Cisco format • It is the default encapsulation on Point to Point and Circuit switched connections • Only use HDLC with other Cisco equipment • Frame Relay • Uses high quality digital facilities • NO ERROR CORRECTION!!! • Handles multiple virtual circuits

  8. WAN Standards • Point-to-Point (PPP) • Built in authentication such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) • PPP can check for link quality during connection establishment • Link Access Procedure Balanced (LAPB) – used by X.25 and has extensive error checking • Link Access Procedure on the D channel (LAPD) – used for signaling and call setup on ISDN

  9. WAN Connection Services

  10. Circuit vs. Packet Switched • Circuit Switched – A PHYSICAL connection through a carrier is established, maintained, and terminated • Packet Switched – Units of data called packets are routed through a network based on the destination address in the packet

  11. Typical Packet Switched Network

  12. Packet/Cell Switched Packet • X.25 – old standard, extensive error correction • Frame Relay – no error correction, moderate cost, very popular CELL • ATM – uses fixed 53 byte length cells to carry data, cost is high • SMDS – Used in MAN’s, high cost, not in widespread use

  13. Dedicated Digital Services • T1, T3, E1, E3 – Widespread, moderate cost, 1.544 Mbps – 44.736Mbps for T1 – T3 • xDSL – Many types such as AsynchronousDSL (ASDL), High Bit RateDSL (HDSL), etc., cost is moderate, bandwidth is high • SONET – very high speed, designed to run on fiber, not for home users

  14. Nationwide SONET Network

  15. Miscellaneous WAN Technologies • Dialup modem – (switched analog) widespread use, low speed, low cost, 56k max bandwidth • Cable Modem – (shared analog) low cost, bandwidth varies, uses coaxial cable • Wireless – requires no cable, use is widespread, cost is high (satellite or microwave)

  16. WAN Routers (Router Internals) • Random Access Memory (RAM/DRAM) • Stores Routing Tables • Packet buffering • Provides temporary memory for running configuration • ARP Cache is kept here • Fast Switching Cache • Packet-hold Queues • All content is LOST when power is lost

  17. WAN Routers (Router Internals) • Nonvolatile random Access Memory (NVRAM) • Stores Backup/Startup Configuration • Retains content when router is powered down

  18. WAN Routers (Router Internals) • Flash Memory • Erasable Programmable Read Only Memory (EPROM) • Holds the Operating System and microcode • Allows software to be updated without removing chips • Content remains when powered down • Multiple Cisco IOS Software can be stored here (depending on space)

  19. WAN Routers (Interface) • Interface • Network connection where packets enter and exit the router • Located either on the motherboard or a separate interface module

  20. WAN Routers- Physical Components • Routers are specialized computers containing: • Central Processing Unit (CPU) • Random Access Memory (RAM) • Basic Input Output System (BIOS) • Operating System (OS) • A motherboard • Physical Input/Output Ports • A power supply and chassis

  21. WAN Routers- Functions of a Router • Physical Interconnectivity • ports • Logical Interconnectivity • Default Routes, Routing Tables • Route calculation and maintenance • Identify Potential routes • Calculate best route based on a formula • Monitor and detect topology changes • Security • Access Control Lists (ACL’s)

  22. WAN Routers- Evaluating Routing Protocols for Performance • Optimality – ability to choose best route • Efficiency – Best use of RAM, CPU, etc. • Robustness – Does the protocol work well even during network failures? • Convergence – How fast can routers agree on network topology? • Scalability – Can my network grow?

  23. WAN Routers- Router Functions • Best Path Determination – routers build routing tables with a list of paths to networks • Switching of packets to proper outgoing interface – routing tables list the interface with the network

  24. WAN Routers- Important Terms • WAN – A collection of LAN’s • Network – a generic collection of related networking mechanisms belonging to a single organization • Internetwork – A collection of loosely related networks that are interconnected • Autonomous system – A network that is relatively self-contained and maintained by one person. You may have connections to other networks.

  25. WAN Routers- Internetworking Scenarios • Routing Within a Network – interior routers, minimal router overhead, possible static routes • Routing Between Adjacent Networks – Networks that are directly connected, Border routers may have summarized information • Routing Between Nonadjacent Networks – most complicated, risk of intrusion is much higher, border routers summarize internal network

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