Wide Area Networking Protocols.ppt

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1、Wide Area Networking ProtocolsOverview1.0 Wide Area Networks2.0 High-Level Data-Link Control Protocol (HDLC)3.0 Point-to-Point Protocol (PPP)4.0 Frame Relay5.0 Integrated Services Digital Network6.0 Dial-on Demand Routing (DDR)1.0Wide Area Networks1.1 Introduction to Wide Area Services1.2 Defining W

2、AN Terms1.2 WAN Connection Types1.3 WAN Protocols1.1Introduction to Wide Area ServicesnTo extend LANs to other LANs at remote sitesnConnecting sites together so information can be exchangednService providers lease or share their already installed connections1.2Defining WAN Terms (WAN Service Provide

3、rs)nCustomer Premises Equipment (CPE)lEquipment that is owned and located at the subscribers premisesnDemarcation (demarc)lThe place where the CPE ends and the local loop portion of the service begins (usually in the “phone-closet”)nLocal LooplConnects the demarc to the closest switching office (CO)

4、nCentral Office (CO) / Point of Presence (POP)lConnects the customers to the providers switching network.nToll NetworklThe switches and facilities, (trunks), inside the WAN providers “cloud”. Synchronous serialAsynchronous serial, ISDNSynchronous serial1.3WAN Connection TypesDedicated Leased lines (

5、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 SwitchingSets up line like a phone call. No data can tra

6、nsfer before the end-to-end connection is established. Use dial-up modems and ISDN. It is used for low-bandwidth data transfers.Packet SwitchingShare bandwidth with other companies to save money. For not constantly data transmission (otherwise using leased line)TelephoneCompanyServiceProviderSpeed u

7、p to 45 MbpsLow-bandwidth data transfersSpeed range from 56K to 2.048M1.4WAN ProtocolsFrame RelaylPacket-switched technology with Data Link and Physical Layer specificationlProvide Dynamic-bandwidth allocation and congestion controlISDN (Integrated Services Digital Network)lVoice and Data transmissi

8、on over existing phone lineslHigher speed than analog dial-up link; good choice as a backup linkLAPB (Link Access Procedure, Balanced)lA connection-oriented protocol at the Data Link layer for use with X.25lVery high overhead; only used if link is very error proneHDLC (High-Level Data Link Control)l

9、Derived from Synchronous Data Link Control (SDLC) created by IBMlA connection-oriented protocol at the Data Link Layer, low overheadlEach vendors HDLC is proprietary for their equipmentPPP (Point-to-Point Protocol)lAn industry-standard protocol, to create point-to-point links between different vendo

10、rs equipmentlAllow authentication and multi-link connections, run over asyn. & syn. links2.0High-Level Data-Link Control Protocol (HDLC)nISO standard, bit-oriented Data Link layer protocolnA point-to-point protocol used on leased linesnDefault encapsulation used by Cisco routers over synchronous ser

11、ial links; or type the following commandslRouter(config-if)# Encapsulation hdlcnEach vendor has a different way for the HDLC protocol to communicate with the Network layer protocolnNo authenticationSynchronous Physical MediaHDLCIPIPXAppleTalkBit-oriented protocols use single bit as control informati

12、on (byte-oriented use entire byte)3.0Point-to-Point Protocol3.1 Introduction to PPP3.2 Point-to-point Protocol Stack3.3 Link Control Protocol (LCP) Configuration Options3.4 PPP Session Establishment3.5 PPP Authentication Methods3.6 Configuring PPP on Cisco Routers3.7 Verifying PPP Encapsulation3.1In

13、troduction to PPPnA Data-link, point-to-point protocol used lOver asynchronous serial (dial up)lOver synchronous serial (ISDN, Leased line)lLCP (Link Control Protocol) to build and maintain data-link connectionsnUse to transport layer-3 packets across a Data-link layernComponents:lEIT / TIA-232-C (f

14、ormerly RS-232) physical layer international standard for serial communicationlHDLC A method for encapsulating datagrams over serial linkslLCP A method of establishing, configuring, maintaining, and terminating the point-to-point connectionlNCP Encapsulating different Network layer protocol across a

15、 PPP data link3.2Point-to-point Protocol StackNetwork LayerIPIPXOthers, e.g. AppleTalkIPCPIPXCPOthersData Link LayerNetwork Control Protocol (NCP)Link Control Protocol (LCP)Authentication, other optionsHigh-Level Data Link Control Protocol (HDLC)Physical LayerSynchronous or Asynchronous Physical Med

16、ia(such as EIA/TIA-232, V.24, V.35, ISDN)PPPServiceProviderTCP/IPAppleTalkPPP EncapsulationTCP/IPIPXAppleTalkIPX3.3Link Control Protocol (LCP) Configuration OptionsLCP offers PPP the following options:nAuthenticationlPAP & CHAPnCompressionlto increase the throughput of PPP connection (Stacker & Pred

17、ictor)nError DetectionlQuality & Magic NumbernMulti-linklstarting in IOS 11.1lSplits the load for PPP over two or more parallel circuits (bundle)3.4PPP Session EstablishmentThree phases of session establishmentnLink-establishment phaselLCP packets are sent by each PP device to configure and test the

18、 linknAuthentication phase (optional)lCHAP or PAP is used to authenticate a linknNetwork-layer protocol phaselNCP to encapsulate multiple Network-layer protocols and then send over a PPP data link3.5PPP Authentication MethodsPassword Authentication Protocol (PAP)nLess securenPasswords are sent in cl

19、ear textnOnly perform upon the initial link establishmentnWhen the PPP link is first established, the remote node sent back the username and password for authentication at the sending routerChallenge Authentication Protocol (CHAP)nUsed at the initial startup of a link and at periodic checkupa challe

20、nge requestA value calculatedwith MD5Check the value, if not match - terminate at once!*MD5 is a one-way hash function3.6Configuring PPP on Cisco RoutersnRouter(config-if)#lEncapsulation ppplConfiguring PPP encapsulation on an interface (serial)nRouter(config)#lHostname lUsername password lCase-sens

21、itive and Plain-text passwordlThe password on both routers must be the samelBoth the local and remote router must be configurednRouter(config-if)#lppp authenticaiton chap | pap lConfiguring the authentication type on an interface (serial)lIf both are chosen, the first one will be used. If the first

22、one failed, the second one will be used.3.7Verifying PPP EncapsulationnRouter#lShow int s0lShow the encapsulation method, protocol support, etc.nRouter#lDebug ppp authenticationlVerify the PPP authentication configuration4.0Frame Relay4.1 Introduction to Frame Relay4.2 Frame Relay Terminology4.3 Dat

23、a Link Connection Identifiers (DLCIs)4.4 Local Management Interface (LMI)4.5 Sub-interface4.6 Mapping Frame Relay4.7 Frame Relay Configuration Tasks4.8 Frame Relay Congestion Control4.9 Committed Information Rate (CIR)4.10 Monitoring Frame Relay4.1Introduction to Frame RelaynFrame Relay works on phy

24、sical and data link layer.nFrame Relay provides 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

25、Identifier.nFrame Relay is more efficient and faster than X.25 because it assumes error checking will be done through higher-layer protocols and application services.nAlso, like X.25, Frame Relay uses both PVCs (Permanent Virtual Circuits) and SVCs (Switched Virtual Circuits), although most Frame Re

26、lay networks use only PVCs. This virtual circuit provides the complete path to the destination network prior to the sending of the first frame.nFrame Relay is used over a variety of network protocols.nFrame Relay interface between the user and the network equipment will transmit and receive frames u

27、sing first-in first-out queuing on a statistically multiplexed circuit4.2Frame Relay TerminologyHub/SwitchDSU/ CSURouterDLCI 16 DSU/CSUUserDemarcCentral OfficeDemarcDSU/ CSUHub/SwitchRouterDLCI 17 DSU/CSUUserFrame actually transverse thisPVCRouter see thisUser onlysee thisFrame Relay network allow u

28、sers to communicate between two DTE devices through DCE devices.123456Remember that before data is sent through the cloud, the virtual circuit is created from end to end.Central OfficeWAN784.3Data Link Connection Identifier (DLCI) AssignmentnFrame Relay virtual circuits (PVCs) are identified by DLCI

29、s.nFrame Relay provider sets up the DLCI numbers to be used by the routers for establishing PVCsnFor 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

30、 network 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.nEach DLCI is locally significant. That means DLCI numbers do not necessarily need t

31、o be unique. 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.nDLCI star

32、t at 16. DLCI 1023 is specific for LMI use, DLCIs 1019 to 1022 address multicastnMap entry indicates static route to destination4.4Local Management Interface (LMI)nThe LMI is a signaling standard between a CPE device (router) and a frame switch. The LMI is responsible for managing and maintaining st

33、atus between these devices. LMI messages provide information about the following:lKeepalives Verify data is flowinglMulticasting Provides a local DLCI PVClMulticast addressing Provides global significancelStatus of virtual circuits Provides DLCI statusnThere are three standard LMI signaling formats

34、are supported:lCisco LMI defined by the Gang of Four (default)lANSI Annex D defined by ANSI standard T1.617lITU-T (q933a) Annex A defined by Q.933nRouters receive LMI information on a frame-encapsulated interface and update the virtual circuit status to one of three different states:lActive state Ev

35、erything is up and routers can exchange information.lInactive state The routers interface is up and working with a connection to the switching office, but the remote router is not working.lDeleted state This means that no LMI information is being received on the interface from the switch. It could b

36、e a mapping problem or a line failure.4.5SubinterfacesnCreating Subinterfaces in order to have multiple virtual circuits on a single serial interface and yet treat each as a separate interface (with different configuration).lDefines logical sub-interfaces on the serial linelEach sub-interface uses a

37、 DLCI to represents the destinations for Frame Relay PVC networklEach sub-interface uses its own sub-networklWork for Partial mesh Frame Relay networknConfiguring subinterfaces actually works to subdivide the Frame Relay network into smaller subnetworks.nSubinterfaces also solve the problem with rou

38、ting protocols that use split horizon.nThere are two types of subinterfaces:lPoint-to-point Used when a single virtual circuit connects one router to another. Each point-to-point subinterface requires its own subnet.lMultipoint Used when the router is the center of a star of virtual circuits. Uses a

39、 single subnet for all routers serial interfaces connected to the frame switch.4.6Mapping Frame RelaynIn order for IP devices at the ends of virtual circuits to communicate, their addresses must be mapped to the DLCIs. nThere are two ways to make this mapping happen:lUse the Frame Relay map command

40、for manually mapping. This is also the only way to configure multiple frame encapsulation types on an interfacelUse 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 c

41、an be insidiously and dynamically mapped to unknown devices.4.7Frame Relay Configuration Tasks (1)nRouter(config-if#lencapsulation frame-relay cisco|ietflSets frame relay encapsulation for connection to non-Cisco Routers (the default encapsulation is for same Cisco Routers)nRouter(config-if)#lframe-

42、relay lmi-type ansi|cisco|q933alSelects LMI typelBeginning with IOS version 11.2, the LMI type is auto-sensed. This enables the interface to determine the LMI type supported by the switch.nRouter(config-if)#lframe-relay map protocol-address cisco|ietf broadcast lDefines how to reach a destinationlTh

43、e broadcast 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.4.7Frame Relay Configuration Tasks (2)

44、nRouter(config)#linterface .sub-interface-number point-to-point|multipointlCreates the logical sub-interface for Frame RelaylGenerally the subinterface number matches the DLCI number but this is not a requirement it only helps in the administration of the interfaces.nRouter(config-if)#lframe-relay i

45、nterface-dlci lAssigns a DLCI to the Frame Relay sub-interface on the router4.8Frame Relay Congestion ControlFrame Relay switch control congestion as follows:nDE (Discard Eligibility) When a Frame Relay router detects congestion on the Frame Relay network, it will turn the DE bit on in a Frame Relay

46、 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.nFECN (Forward-Explicit Congestion Notification) When the Frame Relay network recognizes congestion in t

47、he 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.nBECN (Backward-Explicit Congestion Notification) When the switch detects congestion in the Frame Relay network, it will set the BECN bi

48、t 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.4.9Committed Information Control (CIR)nFrame Relay is based on the assumption that not all customers need to transmit constant data all at the same time. Frame Relay works

49、 best with bursty traffic.nFrame 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).nThe CIR specifies that as long as the data input by a device to the Frame Relay network is below or equal to the

50、CIR, then the network will continue to forward data for the PVC. However, if data rates exceed the CIR, it is not guaranteed.nYou 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.4.10Monitoring Fr