1. Wide Area Networks

2. Announcements and Outline
Design/Mgmt Quiz on Wednesday
Outline is available on the calendar
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
Copyright 2010
John Wiley & Sons, Inc 2

3. 8.1 Introduction
Wide area networks (WANs) Typically built by using leased circuits from common carriers such as AT&T

4. 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
Google Fiber Network

5. Choosing a WAN Link Connection
Purpose of the WAN? Geographic scope? Traffic Requirements?

6. Choosing a WAN Link Connection
Public or Private infrastructure?

7. WAN Services Private: Public: Circuit-Switched Networks
Dedicated-Circuit Networks
Packet-Switched Networks
Public:
Virtual Private Networks

8. 8.21 Circuit Switched Networks – Architecture

9. 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

10. 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

11. 8.22 Dedicated Circuit Services – Basic Architecture

12. 8.22 Dedicated Circuits

13. 8.22 Ring Architecture
Reliability
Performance

14. 8.22 Star Architecture
Easy to manage
Reliability
Performance

15. 8.22 Mesh Architectures

16. 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

17. 8.22 T-Carrier Digital Hierarchy
T-Carrier Designation
DS Designation
Data Rate
DS-0
64 Kbps
T-1
DS-1
1.544 Mbps
T-2
DS-2
6.312 Mbps
T-3
DS-3
Mbps
T-4
DS-4
Mbps

18. 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
51.84 Mbps
Each succeeding SONET hierarchy rate is defined
as a multiple of OC-1

19. 8.22 SONET Digital Hierarchy
SONET Designation
SDH Designation
Data Rate
OC-1
STM-0
51.84 Mbps
OC-3
STM-1
Mbps
OC-9
STM-3
Mbps
OC-12
STM-4
Mbps
OC-18
STM-6
Mbps
OC-24
STM-8
1.244 Gbps
OC-36
STM-12
1.866 Gbps
OC-48
STM-16
2.488 Gbps
OC-192
STM-64
9.952 Gbps
OC-1 52 Mbps $ ,000/mo
OC Mbps $30,000 + /mo
OC Mbps $50,000 +/mo

20. 8.23 Packet Switched Services – Basic Architecture

21. 8.23 Packet Switched Services
Recap: In both circuit switched and dedicated services…
Packet switched services

22. 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

23. 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 & )

24. 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

25. 8.24 Virtual Private Networks
Provides equivalent of a private packet switched network over public Internet Provides low cost and flexibility Disadvantages of VPNs:

26. 8.24 VPN – Basic Architecture

27. 8.24 Layer 3 VPN Using IPSec

28. 8.24 VPN Types
Intranet VPN Extranet VPN Access VPN

29. 8.3 WAN Design Practices
Difficult to recommend best practices Factors used Design Practices

30. 8.3 MAN/WAN Services Summary

31. 8.3 Recommendations Best Practices MAN/WAN

32. 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%

33. 8.4 Improving Circuit Capacity

34. 8.4 Reducing Network Demand