1、Wide Area Networking Protocols,Overview,1.0 Wide Area Networks 2.0 High-Level Data-Link Control Protocol (HDLC) 3.0 Point-to-Point Protocol (PPP) 4.0 Frame Relay 5.0 Integrated Services Digital Network 6.0 Dial-on Demand Routing (DDR),1.0 Wide Area Networks,1.1 Introduction to Wide Area Services 1.2
2、 Defining WAN Terms 1.2 WAN Connection Types 1.3 WAN Protocols,1.1 Introduction to Wide Area Services,To extend LANs to other LANs at remote sites Connecting sites together so information can be exchanged Service providers lease or share their already installed connections,1.2 Defining WAN Terms (WA
3、N Service Providers),Customer Premises Equipment (CPE) Equipment that is owned and located at the subscribers premises Demarcation (demarc) The place where the CPE ends and the local loop portion of the service begins (usually in the “phone-closet”) Local Loop Connects the demarc to the closest swit
4、ching office (CO) Central Office (CO) / Point of Presence (POP) Connects the customers to the providers switching network. Toll Network The switches and facilities, (trunks), inside the WAN providers “cloud”.,Synchronous serial,Asynchronous serial, ISDN,Synchronous serial,1.3 WAN Connection Types,De
5、dicated Leased lines (Point to Point Connection) A pre-established WAN communications path from the CPE, through the DCE switch, to the CPE of the remote site, allowing DTE networks to communicate at any time with no setup procedures before transmitting data.,Circuit Switching Sets up line like a ph
6、one call. No data can transfer before the end-to-end connection is established. Use dial-up modems and ISDN. It is used for low-bandwidth data transfers.,Packet Switching Share bandwidth with other companies to save money. For not constantly data transmission (otherwise using leased line),Telephone
7、Company,Service Provider,Speed up to 45 Mbps,Low-bandwidth data transfers,Speed range from 56K to 2.048M,1.4 WAN Protocols,Frame Relay Packet-switched technology with Data Link and Physical Layer specification Provide Dynamic-bandwidth allocation and congestion control ISDN (Integrated Services Digi
8、tal Network) Voice and Data transmission over existing phone lines Higher speed than analog dial-up link; good choice as a backup link LAPB (Link Access Procedure, Balanced) A connection-oriented protocol at the Data Link layer for use with X.25 Very high overhead; only used if link is very error pr
9、one HDLC (High-Level Data Link Control) Derived from Synchronous Data Link Control (SDLC) created by IBM A connection-oriented protocol at the Data Link Layer, low overhead Each vendors HDLC is proprietary for their equipment PPP (Point-to-Point Protocol) An industry-standard protocol, to create poi
10、nt-to-point links between different vendors equipment Allow authentication and multi-link connections, run over asyn. & syn. links,2.0 High-Level Data-Link Control Protocol (HDLC),ISO standard, bit-oriented Data Link layer protocolA point-to-point protocol used on leased lines Default encapsulation
11、used by Cisco routers over synchronous serial links; or type the following commands Router(config-if)# Encapsulation hdlc Each vendor has a different way for the HDLC protocol to communicate with the Network layer protocol No authentication,Bit-oriented protocols use single bit as control informatio
12、n (byte-oriented use entire byte),3.0 Point-to-Point Protocol,3.1 Introduction to PPP 3.2 Point-to-point Protocol Stack 3.3 Link Control Protocol (LCP) Configuration Options 3.4 PPP Session Establishment 3.5 PPP Authentication Methods 3.6 Configuring PPP on Cisco Routers 3.7 Verifying PPP Encapsulat
13、ion,3.1 Introduction to PPP,A Data-link, point-to-point protocol used Over asynchronous serial (dial up) Over synchronous serial (ISDN, Leased line) LCP (Link Control Protocol) to build and maintain data-link connections Use to transport layer-3 packets across a Data-link layer Components: EIT / TIA
14、-232-C (formerly RS-232) physical layer international standard for serial communication HDLC A method for encapsulating datagrams over serial links LCP A method of establishing, configuring, maintaining, and terminating the point-to-point connection NCP Encapsulating different Network layer protocol
15、 across a PPP data link,3.2 Point-to-point Protocol Stack,PPP,Service Provider,TCP/IP,AppleTalk,PPP Encapsulation,TCP/IP,IPX,AppleTalk,IPX,3.3 Link Control Protocol (LCP) Configuration Options,LCP offers PPP the following options: Authentication PAP & CHAP Compression to increase the throughput of P
16、PP connection (Stacker & Predictor) Error Detection Quality & Magic Number Multi-link starting in IOS 11.1 Splits the load for PPP over two or more parallel circuits (bundle),3.4 PPP Session Establishment,Three phases of session establishment Link-establishment phase LCP packets are sent by each PP
17、device to configure and test the link Authentication phase (optional) CHAP or PAP is used to authenticate a link Network-layer protocol phase NCP to encapsulate multiple Network-layer protocols and then send over a PPP data link,3.5 PPP Authentication Methods,Password Authentication Protocol (PAP) L
18、ess secure Passwords are sent in clear text Only perform upon the initial link establishment When the PPP link is first established, the remote node sent back the username and password for authentication at the sending router Challenge Authentication Protocol (CHAP) Used at the initial startup of a
19、link and at periodic checkup,*MD5 is a one-way hash function,3.6 Configuring PPP on Cisco Routers,Router(config-if)# Encapsulation ppp Configuring PPP encapsulation on an interface (serial) Router(config)# Hostname Username password Case-sensitive and Plain-text password The password on both routers
20、 must be the same Both the local and remote router must be configured Router(config-if)# ppp authenticaiton chap | pap Configuring the authentication type on an interface (serial) If both are chosen, the first one will be used. If the first one failed, the second one will be used.,3.7 Verifying PPP
21、Encapsulation,Router# Show int s0 Show the encapsulation method, protocol support, etc. Router# Debug ppp authentication Verify the PPP authentication configuration,4.0 Frame Relay,4.1 Introduction to Frame Relay 4.2 Frame Relay Terminology 4.3 Data Link Connection Identifiers (DLCIs) 4.4 Local Mana
22、gement Interface (LMI) 4.5 Sub-interface 4.6 Mapping Frame Relay 4.7 Frame Relay Configuration Tasks 4.8 Frame Relay Congestion Control 4.9 Committed Information Rate (CIR) 4.10 Monitoring Frame Relay,4.1 Introduction to Frame Relay,Frame Relay works on physical and data link layer. Frame Relay prov
23、ides connection-oriented, Data Link layer communication via virtual circuits just as X.25 does. These virtual circuits are logical connections created between two DTEs across a packet-switched network, which is identified by a DLCI, or Data Link Connection Identifier. Frame Relay is more efficient a
24、nd faster than X.25 because it assumes error checking will be done through higher-layer protocols and application services. Also, like X.25, Frame Relay uses both PVCs (Permanent Virtual Circuits) and SVCs (Switched Virtual Circuits), although most Frame Relay networks use only PVCs. This virtual ci
25、rcuit provides the complete path to the destination network prior to the sending of the first frame. Frame Relay is used over a variety of network protocols. Frame Relay interface between the user and the network equipment will transmit and receive frames using first-in first-out queuing on a statis
26、tically multiplexed circuit,4.2 Frame Relay Terminology,Hub/Switch,DSU/ CSU,Router DLCI 16,DSU/CSU,User,Demarc,Central Office,Demarc,DSU/ CSU,Hub/Switch,Router DLCI 17,DSU/CSU,User,Frame actually transverse this,PVC Router see this,User only see this,Frame Relay network allow users to communicate be
27、tween two DTE devices through DCE devices.,1,2,3,4,5,6,Remember that before data is sent through the cloud, the virtual circuit is created from end to end.,Central Office,WAN,7,8,4.3 Data Link Connection Identifier (DLCI) Assignment,Frame Relay virtual circuits (PVCs) are identified by DLCIs. Frame
28、Relay provider sets up the DLCI numbers to be used by the routers for establishing PVCs For the IP devices at each end of a virtual circuit to communicate, their IP addresses need to be mapped to DLCIs. This mapping can function as a multipoint deviceone that can identify to the Frame Relay network
29、the appropriate destination virtual circuit for each packet that is sent over the single physical interface. The mappings can be done dynamically through IARP or manually through the Frame Relay map command. Each DLCI is locally significant. That means DLCI numbers do not necessarily need to be uniq
30、ue. Two DLCI numbers can be the same on different sides of a link because Frame Relay maps a local DLCI number to a virtual circuit on each interface of the switch. Each remote office can have its own DLCI number and communicate with the corporate office using unique DLCI numbers. DLCI start at 16.
31、DLCI 1023 is specific for LMI use, DLCIs 1019 to 1022 address multicast Map entry indicates static route to destination,4.4 Local Management Interface (LMI),The LMI is a signaling standard between a CPE device (router) and a frame switch. The LMI is responsible for managing and maintaining status be
32、tween these devices. LMI messages provide information about the following: Keepalives Verify data is flowing Multicasting Provides a local DLCI PVC Multicast addressing Provides global significance Status of virtual circuits Provides DLCI status There are three standard LMI signaling formats are sup
33、ported: Cisco LMI defined by the Gang of Four (default) ANSI Annex D defined by ANSI standard T1.617 ITU-T (q933a) Annex A defined by Q.933 Routers receive LMI information on a frame-encapsulated interface and update the virtual circuit status to one of three different states: Active state Everythin
34、g is up and routers can exchange information. Inactive state The routers interface is up and working with a connection to the switching office, but the remote router is not working. Deleted state This means that no LMI information is being received on the interface from the switch. It could be a map
35、ping problem or a line failure.,4.5 Subinterfaces,Creating Subinterfaces in order to have multiple virtual circuits on a single serial interface and yet treat each as a separate interface (with different configuration). Defines logical sub-interfaces on the serial line Each sub-interface uses a DLCI
36、 to represents the destinations for Frame Relay PVC network Each sub-interface uses its own sub-network Work for Partial mesh Frame Relay network Configuring subinterfaces actually works to subdivide the Frame Relay network into smaller subnetworks. Subinterfaces also solve the problem with routing
37、protocols that use split horizon. There are two types of subinterfaces: Point-to-point Used when a single virtual circuit connects one router to another. Each point-to-point subinterface requires its own subnet. Multipoint Used when the router is the center of a star of virtual circuits. Uses a sing
38、le subnet for all routers serial interfaces connected to the frame switch.,4.6 Mapping Frame Relay,In order for IP devices at the ends of virtual circuits to communicate, their addresses must be mapped to the DLCIs. There are two ways to make this mapping happen: Use the Frame Relay map command for
39、manually mapping. This is also the only way to configure multiple frame encapsulation types on an interface Use the inverse-arp (by default enable) function to perform dynamic mapping of the IP address to the DLCI number but its not as stable as using the map command - because virtual circuits can b
40、e insidiously and dynamically mapped to unknown devices.,4.7 Frame Relay Configuration Tasks (1),Router(config-if# encapsulation frame-relay cisco|ietf Sets frame relay encapsulation for connection to non-Cisco Routers (the default encapsulation is for same Cisco Routers) Router(config-if)# frame-re
41、lay lmi-type ansi|cisco|q933a Selects LMI type Beginning with IOS version 11.2, the LMI type is auto-sensed. This enables the interface to determine the LMI type supported by the switch. Router(config-if)# frame-relay map protocol-address cisco|ietf broadcast Defines how to reach a destination The b
42、roadcast keyword at the end tells the router to forward broadcasts for this interface to this specific virtual circuit. Remember that Frame Relay is a nonbroadcast multiaccess (NBMA) encapsulation method, which will not broadcast routing protocols by default.,4.7 Frame Relay Configuration Tasks (2),
43、Router(config)# interface .sub-interface-number point-to-point|multipoint Creates the logical sub-interface for Frame Relay Generally the subinterface number matches the DLCI number but this is not a requirement it only helps in the administration of the interfaces. Router(config-if)# frame-relay in
44、terface-dlci Assigns a DLCI to the Frame Relay sub-interface on the router,4.8 Frame Relay Congestion Control,Frame Relay switch control congestion as follows: DE (Discard Eligibility) When a Frame Relay router detects congestion on the Frame Relay network, it will turn the DE bit on in a Frame Rela
45、y packet header. If the switch is congested, the Frame Relay switch will discard the packets with the DE bit set first. If your bandwidth is configured with a CIR of zero, the DE will always be on. FECN (Forward-Explicit Congestion Notification) When the Frame Relay network recognizes congestion in
46、the cloud, the switch will set the FECN bit to 1 in a Frame Relay packet header. This will indicate to the destination DCE that the path just traversed is congested. BECN (Backward-Explicit Congestion Notification) When the switch detects congestion in the Frame Relay network, it will set the BECN b
47、it in a Frame Relay packet and send it to the source router, telling it to slow down the rate at which it is transmitting packets.,4.9 Committed Information Control (CIR),Frame Relay is based on the assumption that not all customers need to transmit constant data all at the same time. Frame Relay wo
48、rks best with bursty traffic. Frame Relay providers allow customers to buy a lower amount of bandwidth than what they really might need. This is called the Committed Information Rate (CIR). The CIR specifies that as long as the data input by a device to the Frame Relay network is below or equal to t
49、he CIR, then the network will continue to forward data for the PVC. However, if data rates exceed the CIR, it is not guaranteed. You can use a zero CIR to save money if retransmission of packets is acceptable. However, understand that the DE bit will always be turned on in every frame.,4.10 Monitori
50、ng Frame Relay,show frame-relay lmi command will give you the LMI traffic statistics exchanged between the local router and the Frame Relay switch. show frame pvc command will list all configured PVCs and DLCI numbers. the status of each PVC connection and traffic statistics the number of BECN and F
51、ECN packets received on the router show interface command displays line, protocol, DLCI, and LMI information show frame map command will show you the Network layertoDLCI mappings debug frame lmi command will show output on the router consoles by default. The information from this command will allow you to verify and troubleshoot the Frame Relay connection by helping you to determine whether the router and switch are exchanging the correct LMI information,
