© Synergon Informatika Rt., 1999 Chapter 13 WAN Connectivity Overview

2 Objectives Upon completion of this chapter, you will be able to perform the following tasks: List at least four common issue to be considered when evaluating a WAN service Describe Cisco”s implementation of the following WAN connection type, including the key features of each type: Dialin line via modem Leased lines Dial-up connections services Packet-switched services Identify encapsulation and compression methods for each WAN service type

3 WAN Connectivity Options

4 Network Growth As networks expand, remote connection methods must be closely evaluated

5 Connection Considerations Availability Bandwidth Cost Easy of management Application traffic Routing protocol characteristics

6 Types of Connections Async dialin using modems Dedicated (leased) lines Dial-up connections using a router Packet-switched services Async dialin using modems Dedicated (leased) lines Dial-up connections using a router Packet-switched services Access servers Point-to-point over serial lines Dial-on-demand routing and circuit-switched services X.25, Frame Relay, SMDS/ATM Access servers Point-to-point over serial lines Dial-on-demand routing and circuit-switched services X.25, Frame Relay, SMDS/ATM Services DescriptionCisco Offerings

7 Access Servers Async Ports Dialin Client PSTN Network File Server Server Cisco 2511 Asynchronous dial-up connections allow users access to shared data

8 Point-to-Point Serial Lines Dedicated links continuously available

9 Dial-on-Demand Routing Connections are made only when traffic dictates a need PSTN or ISDN A B C

10 Packet-Switched Service Frame Relay X.25 SMDS ATM Packet-switched networks are multiaccess, and data is carried within frames, packets, or cells

11 Frame Relay Networks Use a frame-based digital technology Have error checking but no error notification or retransmissions Are widely available in the United States and Europe Now support PVCs and SVCs (Cisco IOS Release 11.2) Support connection-oriented service Operate at speeds of 56/64 kbps up to 45 Mbps (T3) Have well-defined specifications

12 X.25 Networks Use a packet-based analog technology Have extensive error checking and retransmissions Are widely available in the Europe; some usage in the United States Now support PVCs and SVCs Support connection-oriented service Typically operate at speeds of 56/64 kbps up to T1/T3 Have well-defined specifications

13 SMDS Networks Use a fast packet-based technology Have no end-to-end error checking or retransmissions Available in part of the United States and Europe Support connectionless service (SMDS) Operate at Ds-1 and DS-3 speeds Have well-defined specifications

14 ATM Networks Use a cell-switching technology Have no end-to-end error checking or retransmissions Available in the United States and growing rapidly in Europe Support both PVCs/SVCs and connectionless service Operate at speeds up to 155 Mbps Have still-evolving implementation standards

15 WAN Encapsulation and Compression Options

16 WAN Encapsulation Protocol X.25/LAPB Frame Relay ISDN/LAPD Dial-up Point-to-Point Switched PPP PSTN HDLC, PPP, LAPB Packets Switched Circuit Switched

17 Encapsulation Command Router (config-if) # Encapsulation encapsulation-type  Defines the encapsulation (framing) type  Encapsulation are protocol-specific

18 LAPB Encapsulation Commands Router (config-if) # Encapsulation lapb [ dte | dce | multi | protocol-name ]  Selects LAPB as the encapsulation type  Uses the multi option allows multiple protocols to be carried within the LAPB frame  Using the protocol-name option allows a single protocol to be carried within the LAPB frame

19 Configuring LAPB Parameter RangeDefault Lapb n1 bits largest available lapb t1 milliseconds lapb n2 retries lapb k window-size1-77 lapb modulo modulos8 or 1288  These parameters alter the retransmission characteristics of LAPB

20 Encapsulation Example Interface serial 0 encapsulation ppp ip address ipx network 10 Interface serial 0 encapsulation ppp ip address ipx network 10 PSTN

21 Serial Compression Techniques Uncompressed (default ) Header compression Payload compression Link compression headerPayload More efficient use of bandwidth

22 Compression Commands Router (config-if) # Ip tcp header-compression [ passive ]  Specifies that headers for TCP traffic will be compressed Router (config-if) # Frame-relay payload-compress  Enables payload compression on a specified poitn-to- point interface or subinterface Router (config-if) # Compress [ predictor | stac ]  Configure software compression for LAPB, PPP, and HDLC for a link

23 Summary WAN services are critical to global networks Some available WAN services: Dialin lines via PSTN Leased lines Dial-on-demand routing Packet-switched or cell-switched networks Some WAN encapsulation options: Cisco HDLC, PPP, LAPB Cisco compression options: Header, payload, link