Chapter 8 Wide Area Networks

Announcements and Outline Announcements Outline 8.1 Introduction 8.2 Services 8.21 Circuit-Switched Networks 8.22 Dedicated-Circuit Networks 8.23 Packet-Switched Networks 8.24 Virtual Private Networks 8.3 Best practice MAN/WAN design 8.4 Improving MAN and WAN Performance 8.5 Implications for Management 2 Copyright 2010 John Wiley & Sons, Inc

8.1 Introduction Wide area networks (WANs) Typically built by using leased circuits from common carriers such as AT&T

8.1 Introduction (Cont.) Regulation of services  Federal Communications Commission (FCC) in the US  Canadian Radio Television and Telecomm Commission (CRTC) in Canada  Public Utilities Commission (PUC) in each state Common Carriers  Local Exchange Carriers (LECs) like Verizon  Interexchange Carriers (IXCs) like Sprint

8.2 MANs/WANs Services 1)Circuit-Switched Networks 2)Dedicated-Circuit Networks 3)Packet-Switched Networks 4)Virtual Private Networks

8.21 Circuit Switched Networks – Architecture

8.21 Circuit Switched Networks Oldest and simplest WAN approach Uses the Public Switched Telephone Network (PSTN), or the telephone networks Provided by common carriers Basic types in use today:  POTS (Plain Old Telephone Service) Via use of modems to dial-up and connect to ISPs  ISDN (Integrated Services Digital Network ) Basic Rate Interface (BRI) – 128 Kbps Primary Rate Interface (PRI) – 1.5 Mbps

8.21 Circuit Switched Services Simple, flexible, and inexpensive  When not used intensively Main problems  Varying quality Each connection goes through the regular telephone network on a different circuit,  Low Data transmission rates Up to 56 Kbps for POTS, and up to 1.5 Mbps for ISDN An alternative  Use a private dedicated circuit Leased from a common carrier for the user’s exclusive use 24 hrs/day, 7 days/week

8.22 Dedicated Circuit Services – Basic Architecture

8.22 Dedicated Circuits

8.22 Ring Architecture Reliability Performance

8.22 Star Architecture Easy to manage Reliability Performance

8.22 Mesh Architectures

8.22 Dedicated Services - T-Carrier Most commonly used dedicated digital circuits in North America Units of the T-hierarchy T-1 T-2 T-3 T-4

8.22 T-Carrier Digital Hierarchy 15 T-Carrier Designation DS Designation Data Rate DS-064 Kbps T-1DS Mbps T-2DS Mbps T-3DS Mbps T-4DS Mbps

8.22 Dedicated Services - Synchronous Optical Network (SONET) ANSI standard for optical fiber transmission in Gbps range  Similar to ITU-T-based, synchronous digital hierarchy (SDH)  SDH and SONET can be easily interconnected SONET hierarchy  Begins with OC-1 (optical carrier level 1) at Mbps  Each succeeding SONET hierarchy rate is defined as a multiple of OC-1

8.22 SONET Digital Hierarchy SONET DesignationSDH DesignationData Rate OC-1STM Mbps OC-3STM Mbps OC-9STM Mbps OC-12STM Mbps OC-18STM Mbps OC-24STM Gbps OC-36STM Gbps OC-48STM Gbps OC-192STM Gbps

8.23 Packet Switched Services – Basic Architecture

8.23 Packet Switched Services Recap: In both circuit switched and dedicated services… Packet switched services 

8.23 Packet Switching Interleave packets from separate messages for transmission  Most data communications consists of short burst of data  Packet switching takes advantage of this burstiness Interleaving bursts from many users to maximize the use of the shared network

8.23 Packet Switched - Service Protocols X.25 Oldest packet switched service (widely used in Europe) Not in widespread use in North America Low data rates (64 Kbps) (available now at Mbps) Asynchronous Transfer Mode (ATM) Newer than X.25; also standardized Data Rates Same rates as SONET: 51.8, 466.5, Mpbs New versions: T1 ATM (1.5 Mbps), T3 ATM (45 Mbps) Provides extensive QoS information Enables setting of precise priorities among different types of transmissions (i.e. voice, video & )

8.23 Packet Switched - Service Protocols Frame Relay Faster than X.25 but slower than ATM NO QoS support (under development) Common CIR speeds: 56, 128, 256, 384 Kbps, 1.5, 2, and 45 Mbps Ethernet Services Most organizations use Ethernet and IP in the LAN and BN. Currently offer CIR speeds from 1 Mbps to 1 Gbps at 1/4 the cost of more traditional services No need to translate LAN protocol (Ethernet/IP) to the protocol used in MAN/WAN services X.25, ATM, & Frame Relay use different protocols requiring translation from/to LAN protocols

8.24 Virtual Private Networks Provides equivalent of a private packet switched network over public Internet Provides low cost and flexibility Disadvantages of VPNs:

8.24 VPN – Basic Architecture

8.24 Layer 3 VPN Using IPSec

8.24 VPN Types Intranet VPN Extranet VPN Access VPN

8.3 WAN Design Practices Difficult to recommend best practices Factors used Design Practices

8.3 MAN/WAN Services Summary

8.3 Recommendations Best Practices MAN/WAN

8.4 Improving Performance MAN/WAN: Handled in the same way as improving LAN performance  By checking the devices in the network,  By upgrading the circuits between computers  By changing the demand placed on the network Device: Upgrade the devices (routers) and computers that connect backbones to the WAN Examine the routing protocol (static or dynamic) Dynamic routing Increases performance in networks with many possible routes from one computer to another Better suited for “bursty” traffic Imposes an overhead cost (additional traffic) – Reduces overall network capacity – Should not exceed 20%

8.4 Improving Circuit Capacity

8.4 Reducing Network Demand