CIS 267 WideArea Networks Lecture Chapter 12

1
CIS 267 Wide-Area NetworksLecture Chapter 12

• Vaughn L. Lucas

2
Wide Area Networking Issues

• Trend towards distributed processing
  architectures to support applications and
  organizational needs.
• Expansion of wide area networking technologies
  and services available to meet those needs.

3
WAN Alternatives
4
High Speed WAN Services

• Frame relay
• ATM
• Asynchronous transmission mode
• SMDS
• Switched multi-megabit data service

5
Integrated Network AccessUsing Dedicated Channels
6
Integrated Network AccessUsing Public Switched
WAN
7
Frame Relay Characteristics

• Designed to eliminate excessive X.25 overhead
• Control signaling takes place on a separate
  logical connection (nodes dont need state tables
  for each call)
• Multiplexing/switching take place at layer 2,
  eliminating a layer of processing
• No hop-by-hop flow/error control

8
ATM and FR Growth Rates, 1998
(ATM Customer base 2,000 Frame Relay Customer
base 45,000)
9
WAN Using Leased Lines
10
WAN Using Frame Relay
11
Frame Relay Networking

• Public switched service, multiple vendors,
  available 1992
• Outgrowth of x.25 newer technology
• Faster than x.25 64kb/s (DS1) to DS3 (45mb/s)
  much cheaper than leased lines
• Many pricing schemes fixed, usage based or
  combinations, may include distance charges

12
Frame Relay Characteristics

• Designed to eliminate excessive X.25 overhead
• Control signaling takes place on a separate
  logical connection (nodes dont need state tables
  for each call)
• Multiplexing/switching take place at layer 2,
  eliminating a layer of processing
• No hop-by-hop flow/error control

13
Some OSI Layer Definitions

• Physical Layer
• Layer 1 of the OSI Model. Concerned with the
  electrical, mechanical, and timing aspects of
  signal transmission over a medium
• Data Link Layer
• Layer 2 of the OSI Model. Converts an unreliable
  transmission into a reliable one
• Network Layer
• Layer 3 of the OSI Model. Responsible for
  routing data through a communication network

14
Traditional Packet Switching
15
Frame Relay Operation
16
Frame Relay Characteristics

• Designed to eliminate excessive X.25 overhead
• Control signaling takes place on a separate
  logical connection (nodes dont need state tables
  for each call)
• Multiplexing/switching take place at layer 2,
  eliminating a layer of processing
• No hop-by-hop flow/error control

17
Frame Relay vs X.25 Error Detection
18
Frame Relay Architecture
19
ATMAsynchronous Transfer Mode

• Also known as cell relay
• Faster than X.25, more streamlined than frame
  relay
• Supports data rates several orders of magnitude
  greater than frame relay
• Data on logical connection is organized into
  fixed-size packets, called cells.
• No link-by-link error control or flow control.

20
ATM Networking

• Asynchronous Transfer Mode BISDN development
• Availability started in 1995
• Private net configurations available now
• ATM LAN switches available now
• Being used as network backbone in many LANs
• Widespread availability as WAN service in
  1998-1999

21
ATM Characteristics

• Uses 53 Byte fixed length packets
• Designed for very fast efficient switching
• Isochronous transmission means guaranteed
  maximum delay
• Can support voice, audio, video streams
• Used for data, voice, multimedia
• Originally designed and intended for WAN use,
  applied to MANs and LANs
• Is a Switched Virtual Circuit service

22
Virtual Channels Virtual Paths

• Logical connections in ATM are virtual channels
• analogous to a virtual circuit in X.25 or a frame
  relay logical connection
• used for connections between two end users,
  user-network exchange (control signaling), and
  network-network exchange (network management and
  routing)
• A virtual path is a bundle of virtual channels
  that have the same endpoints.

23
Advantages of Virtual Paths

• Simplified network architecture
• Increased network performance and reliability
• Reduced processing and short connection setup
  time
• Enhanced network services

24
Virtual-Path/Virtual-Channel Characteristics

• Quality of service
• Switched and semi-permanent virtual-channel
  connections
• Cell sequence integrity
• Traffic parameter negotiation and usage monitoring

25
ATM Cell Format
26
ATM Bit Rate Services
27
FR Rides on ATM on the WAN
28
FR-ATM Interworking
29
Public ATM Network
30
ATM Summary

• High speed, efficiency, and flexible traffic
  control of ATM make it attractive as a universal
  networking technology that can support all types
  of traffic
• Public ATM provider has core network of
  high-performance ATM switches connected with
  high-capacity trunk lines (e.g. SONET)
• Network provider provides smaller ATM switches to
  convert from other protocols