Chapter 11 Wide Area Networking Protocols Objectives Identify PPP operations to encapsulate WAN data on Cisco routers Configure authentication with PPP Understand how Frame Relay works on a large WAN network Configure Frame Relay Local Management Interface maps and subinterfaces Monitor Frame Relay operation in the router Understand the ISDN protocols function groups and reference points Describe how Cisco implements ISDN BRI Defining WAN Terms Customer Premises Equipment CPE Routers Switches FRAD NT1 PC s CSU DSUs Etc Demarcation demarc Point of entry into the Local Loop Point where service providers responsibility begins Usually RJ45 connection Defining WAN Terms Local Loop Connection between Demarc and Central Office Last Mile POTS ISDN ADSL Central Office POP Service providers facilities where traffic enters switching network Toll Network Trunk lines inside the provider s WAN network Switching facilities WAN Connection Types WAN Connection Types Dedicated Usually a leased line Permanent connection T1 T3 Fraction T1 etc Circuit Switched telephone ISDN Dial up service No need for source or destination address Temporary Acts as if a Leased Line for the duration of the connection Packet Switched X 25 Frame Relay ATM PVCs permanent logical circuits Share bandwidth SVC s must be setup each time a connection is required Network Services Hierarchy S w itc h in g C irc u it S w itc h in g L e a s e d L in e s D ia l U p C irc u it s P a c k e t S w itc h in g O rig in a l P a c k e t S w itc h in g X 2 5 F a s t P a c k e t S w itc h in g F ra m e R e la y C e ll re la y Terms Asynchronous Without clocking Events occur in a unpredictable manner Synchronization established with each character Stop Start bits Synchronous Timing provided by a clock signal Modem carrier WAN Support X 25 Frame Packet Switched 3 layer protocol Physical Serial DataLink HDLC Ensures reliable delivery Network PLP Packet Layer Protocol Establish maintain and terminate virtual circuits Up to 9 6 kbs Relay 2 Layer Protocol Physical Serial DataLink Cisco 0r IETF Successor to X 25 Unreliable faster Error Detection Bandwidth on demand T1 maybe T3 speeds Key X 25 Protocols Map to the Three Lower Layers of the OSI Reference Model WAN Support ISDN Voice Data Mulimedia Existing telephone lines Basic Rate Interface BRI 2 64 kbps B earer Channels 128Kbps 1 16 kbps D ata Channel Primary Rate Interface PRI 1 4 Mbps 23 64 kbs B earer Channels 1 64 kbs D ata Channel WAN Support Serial Connection Protocols HDLC Bit oriented Data Link layer ISO standard protocol Specifies a data encapsulation method PtP protocol used on leased lines No authentication can be used No layer 3 protocol identification Proprietary Cisco HDLC LAPB Similar to HDLC More overhead PPP More functional than SLIP Uses NCP to carry different Layer 3 protocols WAN OSI Mapping HDLC Frame Format Point to Point Protocol PPP Purpose Transport layer 3 packets across a Data Link layer point to point link Can be used over asynchronous serial dialup or synchronous serial ISDN media Uses Link Control Protocol LCP Builds maintains data link connections Point to Point Protocol Stack PPP Main Components EIA TIA 232 C Intl Std for serial communications HDLC Serial link datagram default encapsulation method LCP Link Control Protocol Used in P t P connections Establishing Maintaining Terminating NCP Method of establishing configuring Network Layer protocols Allows simultaneous use of multiple Network layer protocols PPP LCP Configuration Options Authentication PAP CHAP Compression Stacker Predictor Error detection Quality Magic Number Aids in detection of loop back conditions down when loopback Multilink Splits the load for PPP over 2 parallel circuits a bundle ppp multilink LCP Link Configuration Link establishment phase Open and configure PPP Authentication phase optional CHAP PAP Verify identity Link quality determination optional Network layer protocol phase Negotiates the proper layer 3 protocol Link Termination PPP Authentication Methods Password Authentication Protocol PAP At start up only Passwords sent in clear text Remote node returns username password username remote router hostname Does not prevent access Challenge Authentication Protocol CHAP Done at start up periodically Challenge Reply Remote router sends a one way hash MD5 Does not prevent access PPP Authentication Password Authentication Protocol PAP PAP is not a strong authentication protocol Passwords are sent across the link in clear text Also known as 2 way handshake PPP Authentication Challenge Handshake Authentication Protocol CHAP CHAP is used to periodically verify the identity of the remote node using a three way handshake CHAP provides protection against playback attacks through the use of a variable challenge value that is unique and unpredictable CHAP does not allow a caller to attempt authentication without a challenge Configuring PPP Step 1 Configure PPP on RouterA RouterB Router config t Router config int s0 Router config if encapsulation ppp Router config if Z Step 2 Define the username password on each router RouterA RouterB RouterA config username RouterB password cisco RouterB config username RouterA password cisco NOTE 1 Username maps to the remote router 2 Passwords must match Step 3 Choose Authentication type for each router CHAP PAP Router Config int s0 Router config if ppp authentication chap Router config if ppp authentication pap Router config if Z Step 4 Verify setup Router sh int s0 PPP Authentication Setup Set hostname on both routers Set username Set password Must be the same on both routers Set authentication type CHAP PAP Both Frame Relay Background High performance WAN encapsulatuon method OSI Physical data Link layer Originally designed for use across ISDN Supported Protocols IP DECnet AppleTalk Xerox Network Service XNS Novell IPX Banyan Vines Transparent Bridging ISO Frame Relay Purpose Provide a communications interface between DTE router DCE equipment teleco switch Connection oriented Data Link layer communication Via virtual circuits Provides a complete path from the source to destination before sending the first frame Frame Relay Terminology Frame Relay Some networks will use a separate router and CSU DSU Some routers have built in cards that allow them to make WAN connections The network device that connects to the frame relay Switch is known as a Frame Relay Access Device FRAD or Frame Relay Assembler Disassembler The frame relay switch is called the Frame Relay
View Full Document
Unlocking...