Unit 10 WANs Chapters 27-29 NT2640.U10.PS1 IP Networking: Unit 10: Slide 1

Class Agenda 11/21/15 Learning Objectives Final Exam is in the next class Unit 9: Discussions and Video Lab Activities will be done in class. Assignments will be given in class. Break Times. 10 Minutes break in every 1 Hour. Note: Submit all Assignment and labs due today.

In this unit, students will demonstrate an: Objectives In this unit, students will demonstrate an: Understanding the WAN Point-to-Point Connections and Protocols Understanding of Frame Relay Concepts, Configuration, and Troubleshooting Steps IP Networking: Unit 10: Slide 3

Point-to-Point WANs Chapter 27 NT2640.U10.PS1 IP Networking: Unit 10: Slide 4 4

WAN types include the following: Point-to-Point Circuit Switching Packet Switching IP Networking: Unit 10: Slide 5

Point-to-Point A point-to-point connection is a single, pre-established path from the customer's network through a carrier network, such as a telco, to a customer's remote network A point-to-point line is usually leased from a carrier and thus is often called a leased line. IP Networking: Unit 10: Slide 6

A circuit switching network allows data connections end points A circuit switched network uses a dedicated connection between sites It is ideal for transmitting data that must arrive quickly in the order it is sent Data is sent in a real time. Mostly for analog data IP Networking: Unit 10: Slide 7

Packet Switching A packet switched network allows data to be broken up into packets and sent across the shared resources Packets are transmitted along the most efficient route to the destination Packet switching is ideal for transmitting data that can handle transmission delays, as is often the case with Web pages and e-mail. IP Networking: Unit 10: Slide 8

Point-to-Point Protocol (PPP) Key features of the Point-to-Point Protocol (PPP): Used on a wide variety of physical interfaces including asynchronous serial, synchronous serial (dial up), and ISDN. Supports multiple Network layer protocols, including IP, IPX, AppleTalk, and numerous others Optional authentication is provided through PAP (2-way authentication) or CHAP (3-way authentication). IP Networking: Unit 10: Slide 9

Point-to-Point Protocol (PPP) It supports multilink connections, load-balancing traffic over multiple physical links. It includes Link Quality Monitoring (LQM) which can detect link errors and automatically terminate links with excessive errors. It includes looped link detection that can identify when messages sent from a router are looped back to that router. This is done through routers sending magic numbers in communications. If a router receives a packet with its own magic number, the link is looped. IP Networking: Unit 10: Slide 10

PPP protocols PPP uses two main protocols to establish and maintain the link. Link Control Protocol (LCP). The Link Control Protocol (LCP) is responsible for establishing, maintaining, and tearing down the PPP link. Network Control Protocol (NCP) The Network Control Protocol (NCP) is used to agree upon and configure Network layer protocols to use (such as IP, IPX, or AppleTalk) IP Networking: Unit 10: Slide 11

PPP Concepts PPP provides several basic but important functions that are useful on a leased line that connects two devices, as reviewed in the following list: Definition of a header and trailer that allows delivery of a data frame over the link Support for both synchronous and asynchronous links A protocol type field in the header, allowing multiple Layer 3 protocols to pass over the same link Built-in authentication tools: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) Control protocols for each higher-layer protocol that rides over PPP, allowing easier integration and support of those protocols IP Networking: Unit 10: Slide 12

The PPP Protocol Field One of the more important features included in the PPP standard, but not in the HDLC standard, is the protocol field. The protocol field identifies the type of packet inside the frame. When PPP was created, this field allowed packets from the many different Layer 3 protocols to pass over a single link. Today, the protocol type field still provides the same function, even for the support of two different versions of IP (IPv4 and IPv6). PPP defines a set of Layer 2 control messages that perform various link control functions. These control functions fall into two main categories: Those needed regardless of the Layer 3 protocol sent across the link Those specific to each Layer 3 protocol IP Networking: Unit 10: Slide 13

PPP Link Control Protocol (LCP) . PPP LCP Features Function LCP Feature Description Looped link detection Magic number Detects if the link is looped, and disables the interface, allowing rerouting over a working route. Error detection Link Quality Monitoring (LQM) Disables an interface that exceeds an error percentage threshold, allowing rerouting over better routes. Multilink support Multilink PPP Load-balances traffic over multiple parallel links. Authentication PAP and CHAP Exchanges names and passwords so that each device can verify the identity of the device on the other end of the link. IP Networking: Unit 10: Slide 14

Basic PPP Configuration VIDEO IP Networking: Unit 10: Slide 15

High Level Data Link Control “Wide Area Networks” introduced the main concepts of HDLC. Briefly, HDLC acts like PPP in many ways. It works on point-to-point serial links. It adds both a header and trailer when encapsulating IP packets, and includes an FCS field in the trailer. And because HDLC and PPP differ, the two routers on both ends of the link must use the same WAN data link protocol (either HDLC or PPP). Because Cisco IOS defaults to use HDLC on serial interfaces, you need to understand it better. However, before leaving the topic of WAN configuration, you should know a little more about HDLC configuration. IOS defaults to use HDLC as the data link protocol, so there are no required commands that relate to Layer 2. IP Networking: Unit 10: Slide 16

Frame Relay Concepts Chapter 28 NT2640-U10-PS1 IP Networking: Unit 10: Slide 17 17

Frame Relay Frame relay is a standard for packet switching WAN communications over high-quality, digital lines. Frame-relay networks: Provide error detection but not error recovery. It is up to end devices to request a retransmission of lost packets. Can provide data transfer up to 1.54 Mbps. Have a variable packet size (called a frame). Can be used as a backbone connection to LANs. Can be implemented over a variety of connection lines (56K, T-1, T-3). Operate at the Physical and Data Link layers of the OSI model IP Networking: Unit 10: Slide 18

Frame Relay Overview Frame Relay networks provide more features and benefits than simple point-to-point WAN links, but to do that, Frame Relay protocols are more detailed. For example, Frame Relay networks are multiaccess networks, which means that more than two devices can attach to the network, similar to LANs. Unlike with LANs, you cannot send a data link layer broadcast over Frame Relay. Therefore, Frame Relay networks are called nonbroadcast multiaccess (NBMA) networks. Also, because Frame Relay is multiaccess, it requires the use of an address that identifies to which remote router each frame is addressed. IP Networking: Unit 10: Slide 19

Components of Frame Relay A leased line is installed between the router and a nearby Frame Relay switch; this link is called the access link. To ensure that the link is working, the device outside the Frame Relay network, called the data terminal equipment (DTE), exchanges regular messages with the Frame Relay switch. These keepalive messages, along with other messages, are defined by the Frame Relay Local Management Interface (LMI) protocol. The routers are considered DTE, and the Frame Relay switches are data communications equipment (DCE). IP Networking: Unit 10: Slide 20

Frame Relay Terms and Concepts Term Description Virtual circuit (VC) A logical concept that represents the path that frames travel between DTEs. VCs are particularly useful when you compare Frame Relay to leased physical circuits. Permanent virtual circuit (PVC) A predefined VC. A PVC can be equated to a leased line in concept. Switched virtual circuit (SVC) A VC that is set up dynamically when needed. An SVC can be equated to a dial connection in concept. Data terminal equipment (DTE) DTEs are connected to a Frame Relay service from a telecommunications company. They typically reside at sites used by the company buying the Frame Relay service. Data communications equipment (DCE) Frame Relay switches are DCE devices. DCEs are also known as data circuit-terminating equipment. DCEs are typically in the service provider’s network. Access link The leased line between the DTE and DCE. Access rate (AR) The speed at which the access link is clocked. This choice affects the connection’s price. Committed Information Rate (CIR) The speed at which bits can be sent over a VC, according to the business contract between the customer and provider. Data-link connection identifier (DLCI) A Frame Relay address used in Frame Relay headers to identify the VC. Nonbroadcast multiaccess (NBMA) A network in which broadcasts are not supported, but more than two devices can be connected. Local Management Interface (LMI) The protocol used between a DCE and DTE to manage the connection. Signaling messages for SVCs, PVC status messages, and keepalives are all LMI messages. IP Networking: Unit 10: Slide 21

Frame Relay Standards The definitions for Frame Relay are contained in documents from the International Telecommunications Union (ITU) and the American National Standards Institute (ANSI). The Frame Relay Forum a vendor consortium, originally defined several Frame Relay specifications, many of which predate the original ITU and ANSI specifications, with the ITU and ANSI picking up many of the forum’s standards. (The Frame Relay Forum has disbanded, because its mission was complete.) IP Networking: Unit 10: Slide 22

Frame Relay Configuration and Troubleshooting Chapter 29 NT2640. U10 Frame Relay Configuration and Troubleshooting Chapter 29 NT2640.U10.PS1 IP Networking: Unit 10: Slide 23 23

Frame Rely VIDEO IP Networking: Unit 10: Slide 24

All answers to overdue labs should be submitted in the next class. Lab Activities. Complete 10 Lab in class. All answers to overdue labs should be submitted in the next class. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 4: Slide 25

Unit 10 assignment will be given in class. © 2011 ITT Educational Services Inc. NT-2640 Wan Technologies: Unit 4: Slide 26