Chapter 14 Wide Area Networks

Introduction ►The main difference between LAN and WAN is distance ►Generally WAN services are leased from service providers ►The idea of using WAN protocols is to change networks with large distances between them into LAN-like connected network

Defining WAN Terms

☼Customer premises equipment: (CPE) Customer premises equipment (CPE) is equipment that’s owned by the subscriber and located on the subscriber’s premises. ☼Demarcation point: The demarcation point is the precise spot where the service provider’s responsibility ends and the CPE begins. It’s generally a device in a telecommunications closet owned and installed by the telecommunications company (telco). It’s your responsibility to cable (extended demarc) from this box to the CPE, which is usually a connection to a CSU/DSU or ISDN interface. ☼Local loop: The local loop connects the demarc to the closest switching office, which is called a central office. ☼Central office (CO): This point connects the customer’s network to the provider’s switching network. Good to know is that a central office (CO) is sometimes referred to as a point of presence (POP). ☼Toll network: The toll network is a trunk line inside a WAN provider’s network. This network is a collection of switches and facilities owned by the ISP.

Data Terminal Equipment (DTE) & Data Communicational Equipment (DCE) ►All CISCO serial interfaces are DTE and they need a DCE to provide clock rate to them ►The Channel Service Unit/ Data Service Unit (CSU/ DSU) provides clock rate and makes connection between Digital LAN network & Digital WAN network ►The modem provides clock rate and makes connection between Digital LAN network & Analogue WAN network

Cables Major cables are Serial cables: DB-60 pin from router side and EIA/TIA-232 EIA/TIA-449 V.35 X.21 EIA-530(DTE only) at CSU/DSU side WAN Services focus on: Layer 2 Layer 1 Encapsulation WAN encapsulation protocols HDLC, PPP, Frame Relay, X.25, ATM, LAPB, LAPD, PPPoE, Cable, DSL, MPLS

WAN Connection Types All these encapsulation protocols make error detection since they all use CRC in the FCS of the frame LAPD is the only protocol who by default make Error Correction, PPP also support error correction but it’s not enabled by default

Leased lines ►referred to as a point-to-point or dedicated connection ►pre-established WAN communications ►no hard setup procedures are required ►expensive ►synchronous serial lines ►up to 45Mbps ►frequently use HDLC and PPP

High Level Data Link Control (HDLC) Protocol at Data Link layer. Encapsulate only one Network Layer protocol (IP, IPX, or Apple Talk) at the same link. Work only on Synchronous Interfaces (Serial, BRI) and is the default encapsulation on all CISCO Serial Interfaces. Does not have Authentication, Callback, or Dynamic addressing capability. Work only on similar vendors. Point-To-Point Protocol (PPP) Protocol at Data Link layer. Can Encapsulate several Network Layer protocol (IP, IPX, or Apple Talk) at the same link. Work on Synchronous Interfaces (Serial, BRI) and Asynchronous Interfaces (Aux). Support Authentication, Callback, and Dynamic addressing capability. Can Work on different vendors.

PPP uses 1- LCP Line Control Protocol -It is a method for Establishing, configuring maintaining and terminating PPP connection -LCP offers different PPP encapsulation options: -authentication -compression -error detection -multilink -PPP callback 2- NCP Network Control Protocol allow PPP to simultaneous use of multiple network layer protocols, for example IPCP ( Internet Protocol Control Protocol)

PPP Session Establishment 1. Link establishment phase each router sends LCP packet to configure and test the link, the LCP packet contains the option field to negotiate about authentication, compression, data size 2.Authentication phase using PAP or CHAP 3.Network layer protocol phase the PPP will use NCP to choose the network layer like IP

Password Authentication Protocol (PAP) Two-way Handshake Remote Router sends his user name and password and continue until authentication is acknowledged or connection is terminated Password is sent in clear text Remote Router is in control of the frequency and timing of the login attempts Challenge Handshake Authentication Protocol (CHAP) Three-Way Handshake Local Router sends “Challenge”, the remote router. Response with a value calculated using one-way hash function MD5 based on Password and Challenge message The local router checks the response by his own expected hash if the value match authentication is acknowledged or connection is terminated The hash value is unique and random (actual password is not sent across the link) Local Router controls the frequency and timing of challenges PPP Authentication Methods

Configuring PPP Router(config)#hostname RouterA RouterA(config)#enable secret cisco RouterA(config)#username RouterB password cisco RouterA(config)#int s0 RouterA(config-if)#encapsulation ppp RouterA(config-if)#ppp authentication chap pap RouterA(config-if)#ppp pap sent-username RouterA password cisco

Viewing PPP Status RouterA#sh int s0 1.Authenticated but without checking IPsUP LCPOpen Open: IPCP Check validity of IPs using command: Router#sh cdp neighbors detail 2.Wrong password or user name UPDown LCPClosed Closed: IPCP, CDPCP 3.Mismatched encapsulation UPDown LCPREQsent Closed: IPCP, CDPCP RouterA#debug ppp authentication

Packet Switching ►always connected (like leased line) ►bandwidth sharing ►synchronous serial ►56Kbps to 45Mbps ►use virtual circuit ►to send data constantly DO NOT USE PACKET SWITCHING ►frame relay and X.25 are packet switching technologies

Frame Relay ►saves money ►high performance ►successor of X.25 but does not use error correction ►Non Broadcast Multi Access NBMA (i.e. by default no broadcast is passing through it) ►dynamic bandwidth allocator ►connection oriented data-link technology ►deals with data-link layer and physical layer ►in data-link layer frame-relay encapsulates information from the upper OSI layers, as example IP traffic would be encapsulated into a frame format that can be transmitted over frame-relay link ►in physical layer the same serial cables that support ppp support frame-relay, they are: EIA/TIA-232, EIA/TIA-449, V.35, X.21 EIA/TIA-530

Why we use Frame Relay Frame-relay reserves the leased B.W to you, this B.W is a part of a shared B.W (let’s say 256 Kbps of Mbps) When the rest of the B.W is not used you can use it, this is offered by packet-switch nets Frame-relay sites will share telecommunication company backbone net Telecommunication company switches are responsible of mapping the connections between the sites

Frame Relay Structure

Frame Relay Terminology Access Rate CIR Access Rate: the maximum speed that frame relay interface can transmit CIR (Committed Information Rate): the maximum B.W that your service provider guarantee to be delivered T1 Link Mbps 256 Kbps 128 Kbps 256 Kbps 64 Kbps T1: Mbps a b c

Supposing link a and link b are not transmitting right now then link c can extend beyond the 64 Kbps and use all available B.W that may reach to Mbps Any sent data more than CIR is flagged with the Discard Eligibility (DE)= 1 When congestion happens in frame-relay switch, it sends Backward Explicit Congestion Notification (BECN) to the source, sends Forward Explicit Congestion Notification (FECN) to the destination, and starts deleting any packet with DE= 1 When notifications reach source and destination they both start using flow control

DLCI Data Link Connection Identifier DLCI is a number that identify the logical circuit between router and frame-relay switch ( ), it is supplied by provider. Router(config-if)#frame-relay interface-dlci 400 Local DLCI Global DLCI

LMI Local Management Interface Signaling standard between router and frame relay switch LMI is responsible for managing the connection and maintaining the status between devices It will provides messages about Keepalive: verify that data is flowing Multicasting: allow efficient distribution of routing information and ARP requests over frame relay network. Multicasts use DLCI 1019 – 1022 Global addressing: allow global significant making frame relay cloud to work exactly like LAN Status of virtual circuit: Active: every thing is up and routers can exchange information Inactive: remote router is not working Deleted: no LMI is being received from switch could be line failure

LMI Types: Cisco (also called gang of four) ANSI Q.933A Router(config-if)#frame-relay lmi-type cisco ansi q933a Auto sensed in 11.2 or newer

DLCI Mapping Dynamic Mapping x Static Mapping In order For each router to get to the remote router,it will built Mapping Table in one of two way : 1.Dynamic Mapping using Inverse ARP. 2.Static Mapping. Both map Local DLCI no. with Remote Router IP address.

Router(config)#frame-relay inverse-arp protocol DLCI Protocol: IP, IPX, Apple Talk DLCI: DLCI of the interface we want to exchange IARP IARP is ON by default

Frame Relay switch builds mapping table by doing the following: 1.Reads source DLCI 2.Searches the opposite DLCI 3.Sends the slot port that is connected to the destination

Static Mapping Static mapping is used to spread broadcast (for example to publish RIP) Router(config-if)#frame-relay map protocol destination_address local_DLCI broadcast Frame Relay Encapsulation Types Cisco (default) IETF Internet Engineering Task Force Router(config-if)#encapsulation frame-relay Router(config-if)#encapsulation frame-relay ietf

Frame Relay Topologies

Star (Hub and Spoke) Least expensive Topology Most Poplar Use single interface Must use subinterfaces to connect to multiple PVCs Full Mesh Costly Needs direct connection to each site (many physical interfaces) Redundancy Partial Mesh Not all sites have direct access to all other sites

Configuring Frame Relay RouterA(config)#int s0 RouterA(config-if)#ip add RouterA(config-if)#no shut RouterA(config-if)#encapsulation frame-relay RouterA(config-if)#frame-relay interface-dlci 100 No static mapping is required because IARP is on but if you turn it off then static mapping will be like this: RouterA(config-if)#frame-relay map ip broacast RouterB(config)#int s0 RouterB(config-if)#ip add RouterB(config-if)#no shut RouterB(config-if)#encapsulation frame-relay RouterB(config-if)#frame-relay interface-dlci 400 RouterB(config-if)#frame-relay lmi-type ansi No static mapping is required because IARP is on but if you turn it off then static mapping will be like this: RouterB(config-if)#frame-relay map ip broacast

Configuring Subinterfaces Point-to-Point Each point-to-point subinterface requires it’s own subnet Subinterfaces act like leased lines Multipoint Use single subnet so it saves address space Subinterfaces act like NBMA so they do not solve split-horizon problem

Configuring Point-to-Point RouterA(config)#int s0/0 RouterA(config-if)#no ip add RouterA(config-if)#no shut RouterA(config-if)#encapsulation frame-relay RouterA(config-if)#int s0/0.110 point-to-ponit RouterA(config-subif)#ip add RouterA(config-subif)#frame-relay interface-dlci 110 RouterA(config-subif)#bandwidth 64 RouterA(config-subif)#int s0/0.120 point-to-ponit RouterA(config-subif)#ip add RouterA(config-subif)#frame-relay interface-dlci 120 RouterA(config-subif)#bandwidth 64 S0/ DLCI 110 S0/ DLCI 120 RouterA RouterB RouterC

Configuring MultiPoint RouterA(config)#int s0/0 RouterA(config-if)#no ip add RouterA(config-if)#no shut RouterA(config-if)#encapsulation frame-relay RouterA(config-if)#int s0/0.2 multiponit RouterA(config-subif)#ip add RouterA(config-subif)#bandwidth 64 RouterA(config-subif)#frame-relay map ip broadcast RouterA(config-subif)#frame-relay map ip broadcast RouterA(config-subif)#frame-relay map ip broadcast S0/ DLCI 120 DLCI 130 DLCI

Configuring 2500 Router to act like Frame Relay Switch 2500(config)#frame-relay switching 2500(config)#int s0 2500(config-if)#no ip add 2500(config-if)#no shut 2500(config-if)#clock rate (config-if)#encapsulation frame-relay 2500(config-if)#frame-relay intf-type dce 2500(config-if)#frame-relay route 110 interface s (config-if)#int s1 2500(config-if)#no ip add 2500(config-if)#no shut 2500(config-if)#clock rate (config-if)#encapsulation frame-relay 2500(config-if)#frame-relay intf-type dce 2500(config-if)#frame-relay route 220 interface s0 110

2600A2600B 2500 S0/1 DLCI 110 IP /30 S0/0 DLCI 220 IP /30 S0S1 Frame Relay Switch

Router#sh int s0/0 To view encapsulation, LMI DLCI (default 1023, ansi or q.933a 0), B.W, MTU, Keepalive, MAC, Status of interface Router#sh frame-relay map To view value of DLCI, IP of next hop, MAPPING TYPE [dynamic (IARP), static (broadcast)] Router#sh frame-relay pvc To view PVC status, no. of each type of PVC, value of DLCI, presence of congestion, presence of packets with DE= 1, BECN and FECN Show Frame-relay CMDs

Circuit Switched ►like phone call ►low cost ►no data can transfer before an end-to-end connection is established ►uses dial-up modems or ISDN ►low-bandwidth ►asynchronous serial

ISDN (Integrated Service Digital Network) ►a replacement to the traditional analogue modem ►features: 1.Ability to carry variety of user traffic, video, telex, and telephone, in the same time 2.Faster call setup (less than a second) by using D-channel (Delta-channel) which is responsible of call setup, alarm messages (signaling information) 3.Faster data transfer rate using B-channel (Bearer-channel) (64Kbps), each B- channel can carry one type of data

ISDN Standard Access Methods BRI Basic Rate Interface 2B+1D 2x64K+1x16K(max B.W)= 144Kbps PRI Primary Rate Interface USA and Japan 23B+1D 23x64K+1x64K(max B.W)= T Mbps Europe 30B+1D 30x64K+1x64K(max B.W)= 2.048Mbps ~~~~

BRI and PRI Call Process 1.The D-channel from the local router to the local switch comes up 2.The ISDN switch uses Signaling System 7 SS7 to setup a path to remote switch 3.The remote switch setup the D-channel link to the remote router 4.The B-channels are then connected end to end

ISDN Components BRI U TE1 NT1 U TE1 NT1 S/T U NT1 S/T TA R U S/T TA R NT1 NT2 S/T ‼Function (Devices) Native ISDN (TE1): device with BRI interface Non-native ISDN (TE2): device without BRI interface (serial only) ‼Reference Point (Interface cables) R S T U ISDN Service Provider

Router(config)#isdn switch-type basic-ni to define type of switch of provider Router(config)#int bri0 Router(config-if)#isdn spid1 123… a SPID is a number supplied by the provider to identify line configuration of BRI service Router(config-if)#isdn spid2 123… ISDN Basic Configuration 1.The message reaches the router and be compared with R.T, the router determines the exit interface. If it is the BRI then 2.Check that is the message allowed to pass through DDR, if yes then establishment of call (D-channel is working) 3.The router determines the next hop and determines how to call it 4.Wait 120 sec idle then disconnect if there is no traffic Dial- on Demand Routing DDR

1.Define static routes 2.Define the interest traffic (also known as dialer list) 3.Dialer information (no. to call) + BRI interface (on which dialer list will applied) Configuring DDR ISDN Network BRI1 RouterA BRI0 RouterB Step 1: Define static routes RouterA(config)#ip route RouterA(config)#ip route RouterA(config)#ip route bri1

Step 2: Define the interest traffic (also known as dialer list) RouterA(config)#dialer list 1 protocol IP permit OR RouterA(config)#dialer list 1 protocol IP list 110 RouterA(config)#access-list 110 permit tcp any any eq telnet Step 3: Dialer information (no. to call) + BRI interface (on which dialer list will applied) RouterA(config)#int bri1 RouterA(config-if)#ip address RouterA(config-if)#no shut RouterA(config-if)#encapsulation ppp RouterA(config-if)#ppp authentication chap RouterA(config-if)#dialer-group 1 RouterA(config-if)#dialer string OR RouterA(config-if)#dialer map IP name RouterB RouterA(config-if)#dialer idle-timeout 120 RouterA(config-if)#dialer load-threshold 125

To view current call, phone number, and time left to end call Router#sh isdn active To check for switch connectivity problems Router#sh isdn status To view number of reached dialer string, idle time out of B-channel, and good information about dialer Router#sh isdn dialer To view layer 2 information only Router#sh isdn q921 To view layer 3 information, including call setup and teardown Router#sh isdn q931 To debug using call setup and teardown activity Router#debug dialer Router#isdn disconnect bri0 or Router(config-if)#shutdown Show ISDN CMDs

Cable and DSL How to select 1.Speed 2.Security 3.Popularity 4.Customer Satisfaction

Cable 1.Headend 2.Distribution network: HFC Hybrid Fiber-Coaxial architecture with customers 3.DOCSIS (data over cable service interface specification)

Digital Subscriber Line (DSL) Most popular types are: Symmetrical DSL Asymmetrical DSL But The term xDSL covers a number of DSL variations, such as ADSL, high-bit-rate DSL (HDSL), Rate Adaptive DSL (RADSL), Synchronous DSL (SDSL), ISDN DSL (IDSL), and very-high-data-rate DSL (VDSL) which is employed by cisco to build new technology called Cisco Long Range Ethernet (LRE) with speeds from 5 to 15Mbps (full duplex) at distances up to 5,000 feet traveling over existing twisted-pair wiring