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WANs and Router Basics
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  1. WANs and Router Basics Semester 2 Chapter 2: WANs & Routers Chapter 3: Router CLI By: Allan Johnson

  2. Table of Contents • WAN Devices • WAN Standards • WAN Technologies • Router Basics • Router User Interface

  3. WAN Devices Table of Contents

  4. WAN Services • WANs provide for the exchange of data packets/frames between routers/bridges and the LANs they support. • A WAN interconnects LANs that are usually separated by large geographic areas. • WANs connect devices. Such devices include...

  5. Routers • Routers offer many services including: • Internetworking • WAN serial interfaces • Routers can operate as... • Internal Routers • Backbone Routers • Area Border Routers • Autonomous System Boundary Routers

  6. WAN Bandwidth Switches • Service provider equipment that connects to WAN bandwidth for voice, data and video communications.

  7. Modems • Also called CSU/DSUs (channel service units/digital service units) • Interface with voice-grade connection in order to convert analog signal to digital. • Represents the DCE side of the DTE/DCE connection. • More on DTE/DCE later

  8. Communication Servers • Concentrates dial-in and dial-out services. • Equipment is usually at the service provider’s site.

  9. WAN Standards Table of Contents

  10. WAN Standards • What layers of the OSI model do WAN standards describe? • Physical and Data Link Layers

  11. WAN Physical Layer • Protocols that describe how to provide electrical, mechanical, operational, and functional connections for WAN services. • These services are most often obtained from WAN service providers such as RBOCs, alternate carriers, post-telephone, and telegraph (PTT) agencies. • Describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE).

  12. WAN Physical Layer • Typically, the DCE is the service provider and the DTE is the attached device. • In this model, the services offered to the DTE are made available through a modem or a CSU/DSU.

  13. WAN Physical Layer • Several physical layer standards specifying this interface between the DTE & DCE are... • EIA/TIA-232 • EIA/TIA-449 • V.24 • V.35 • X.21 • G.703 • EIA-530

  14. WAN Data-Link Layer • WAN data link protocols describe how frames are carried between systems on a single data link. • They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services. • WAN standards are defined and managed by a number of recognized authorities, including the following agencies: ITU-T, ISO, IETF, & EIA

  15. WAN Data-Link Encapsulations • High-Level Data Link Control (HDLC) • Cisco default encapsulation; typically used between routers running Cisco IOS; replacing SDLC • Streamlined: no windowing or flow control • may not be compatible with different vendors because of the way each vendor has chosen to implement it. • HDLC supports both point-to-point and multipoint configurations with minimal overhead

  16. WAN Data-Link Encapsulations • Frame Relay • uses high-quality digital facilities; • uses simplified framing with no error correction mechanisms (connectionless!!); • it can send Layer 2 information much more rapidly than other WAN protocols

  17. WAN Data-Link Encapsulations • PPP (Point-to-Point Protocol) • Developed by IETF; replacing SLIP • Contains a field to identify the network layer protocol • PPP can check for link quality during connection establishment • Supports PAP (Password Authentication Protocol) & CHAP (Challenge Handshake Authentication Protocol)

  18. WAN Technologies Table of Contents

  19. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  20. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  21. Dedicated Digital Services Dedicated Digital Services provide full-time connectivity through a point-to-point link • T series in U.S. and E series in Europe • Uses time division multiplexing to “slice up” data and assign time slots for transmissions • T1 = 1.544 Mbps • T3 = 44.736 Mbps • E1 = 2.048 Mbps • E3 = 34.368 Mbps • Uses twisted pair & fiber • Extremely popular • Moderate cost

  22. Dedicated Digital Services • Digital Subscriber Lines (xDSL); the x stands for a family of technologies • New WAN Technology for home use; decreasing bandwidth with increasing distance from the phone companies CO. • Data rates as high as 51.84 Mbps but more common to be in the 100s of Kbps • Varieties include HDSL, SDSL, ADSL, & VDSL • Moderate expense and getting cheaper

  23. Dedicated Digital Services • Synchronous Optical Network (SONET) • Specialized high bandwidth technology for use at various Optical Carrier speeds (OC) ranging from 51.84 Mbps (OC-1) to 9,952 Mbps (OC-192) • Uses lasers to divide the wavelength of the light into sections that can carry large amounts of data (Wave Division Multiplexing) • Very expensive; used by large ISPs and other Internet backbone entities.

  24. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  25. Analog Services • Dial-up Modems (switched analog) • Limited to 56 kbps • Works with existing phone network • Low cost and widespread usage

  26. Analog Services • Cable Modems (Shared Analog) • Puts data signals on the same cable as television signals • Increasing in popularity • Maximum bandwidth can be 10 Mbps, though this degrades as more users attach to a given network segment (behaving like an unswitched LAN) • Cost is relatively low; usage is small but increasing; the medium is coaxial cable.

  27. Terrestrial Bandwidths typically in the 11 Mbps range Cost is relatively low Line-of-sight is usually required Usage is moderate Satellite Can serve mobile users and remote users Usage is widespread Cost is very high Analog Services Wireless

  28. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  29. Circuit Switched Services • Plain Old Telephone System (POTS) • Not a computer data service but... • POTS is an important component of our communication infrastructure and • It is still the standard for designing reliable networks

  30. B D B Circuit Switched Services • Integrated Services Digital Network (ISDN) • Historically important--first dial-up digital service • Cost is moderate; max. bandwidth = 128 kbps for BRI (Basic Rate Interface) • 2 B channels @ 64kps and 1 D channel @ 16kps • B channels are voice/data channels; D for signaling

  31. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  32. Packet Switched Services • X.25 (Connection-oriented) • Older WAN technology developed in 1970s • Reliable--X.25 has been extensively debugged and is now very stable--literally no errors in modern X.25 networks • Store & Forward--Since X.25 stores the whole frame to error check it before forwarding it on to the destination, it has an inherent delay (unlike Frame Relay) and requires large, expensive memory buffering capabilities.

  33. Packet Switched Services • Frame Relay (Connectionless) • More efficient and much faster than X.25 • Packet switched version of ISDN (which is circuit switched); data rates up to 44.736Mbps with 56kbps and 384kbps being the most popular • Used mostly to forward LAN IP and IPX packets but can be used to forward other types of traffic • Primary competitive advantage is its low cost

  34. WAN Technologies Overview • Analog • Dial-up modems • Cable modems • Wireless • Dedicated • T1, E1, T3, E3 • xDSL • SONET Switched • Packet Switched • X.25 • Frame • Relay • Circuit Switched • POTS • ISDN • Cell Switched • ATM • SMDS

  35. Cell Switched Services • Asynchronous Transfer Mode (ATM) • Relatively new WAN Technology related to broadband ISDN; max. bandwidth = 622 Mbps • Developed in order to provide one technology for both WANs and LANs to transport data, video, and voice. (High Cost) • Key Benefits: • One network for all traffic--voice, data, video • Compatible with current wiring infrastructure (cable plant) • Very flexible and scalable • Simplifies network management

  36. Cell Switched Services • Switched Multimegabit Data Service (SMDS) • Closely related to ATM; SMDS is the MAN (Metropolitan Area Network) implementation of ATM • High Cost with max. bandwidth 44.736 Mbps

  37. WAN Technologies Review

  38. Router Basics Table of Contents

  39. RAM NVRAM Flash ROM Console Interfaces Auxiliary Internal Components

  40. RAM • Temporary storage for router configuration files • RAM content is lost on power down or restart • Stores... • Routing tables • ARP cache • Fast switching cache • Packet buffering • And Packet hold queues

  41. NVRAM • Non-volatile RAM • Stores backup/startup configuration files • Content is not lost when router is powered down or restarted.

  42. Flash • EEPROM (Electronically Erasable Programmable Read-Only Memory) • Holds the Cisco IOS (Internet Operating System) • Allows updating of software without replacing the Flash chip • Multiple versions of IOS can be stored • Retained on power down

  43. ROM • Contains POST (Power On Self Test) • A bootstrap program (loads the Cisco IOS) • And operating system software • Backup, trimmed down version of the IOS • Upgrades require installing new chip set

  44. Interfaces • Network connections through which packets enter and exit the router • Attached to the motherboard or as separate modules.

  45. Labs • Before moving on to Ch. 3, make sure you have done both of the required labs for Ch. 2 • Lab 2.2.2 • Lab 2.2.3.2

  46. Router User Interface Table of Contents

  47. Means you’re in user mode User EXEC Modes • User mode • Limited mode used for checking the routers status, looking at routing tables, etc. • You cannot configure the router • Once you’ve typed the password to enter user mode, you will see the > prompt. The word “Router” will be the name of the router. Password: Router>

  48. Means you’re in privileged mode Privileged EXEC Modes • Privileged mode • Does everything User mode does • Full power to configure the router • In user mode, you enter the command “enable” and then the privileged password Router> enable Password: Router#

  49. Command Lists • To get a list of commands available in either user mode or privileged mode, enter a ? at the prompt. Router> ? Router# ? • Since the available commands will be more than the screen can hold, you will get the --More-- message at the bottom. • Hitting the space bar will advance the screen to show the next page.

  50. The Router returned all the available commands for “show” Getting Help on a Command • The ? can be used with a partial command to learn all the available commands that match what you entered. • To use this help feature, enter the partial command, then tap the space bar, then type ? • For example... Router# show ? ip flash: interfaces ipx version parser