1 / 25

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?).

feleti
Télécharger la présentation

WAN’s and Routers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related