1. Business Data Communications, 4e
Chapter 15: LAN Systems
Business Data Communications, 4e

2. High-Speed LANs Why? Examples
Extraordinary growth in speed, power, and storage capacity of PCs
Increasing use of LANs as computing platforms
Examples
Server farms
Workgroups with “power” requirements
High-speed backbones

3. High-Speed LANs

4. Traditional Ethernet Ethernet and CSMA/CD (IEEE 802.3)
Carrier sense multiple access with collision detection
Four step procedure
If medium is idle, transmit
If medium is busy, listen until idle and then transmit
If collision is detected, cease transmitting
After a collision, wait a random amount of time before retransmitting
Carrier Sense
See P. 405
Collision Detection
Back-Off
(Binary Exponential Back-Off Algorithm)

5. IEEE 802.3 Frame Format Preamble: 10101010…
SFD: Start of Frame Delimiter ( )
DA: Destination Address
SA: Source Address
FCS: Frame Check Sequence (32-bit CRC)
MAC Address
(Physical Address)

6. MAC Address Format 00-E0-18-2C-B9-DE Example: 00:E0:18:2C:B9:DE
24 bits
24 bits
Vendor
Interface
00-E0-18-2C-B9-DE
Example:
00:E0:18:2C:B9:DE
Broadcast Address: FF-FF-FF-FF-FF-FF
Vendor Code:

7. 802.3 Medium Notation
10Base-T
Notation format: <data rate in Mbps><signaling method><maximum segment length in hundreds of meters>
e.g 10Base5 provides 10Mbps baseband, up to 500 meters
T and F are used in place of segment length for twisted pair and fiber

8. BaseX Media Options

9. Fast Ethernet (100Mbps) Easy to integrate with existing systems
Can use UTP (-TX) or fiber (-FX)
Uses star-wired topology, using a central multiport repeater (broadcast method)
If NICs support full-duplex mode, switched hub must be used

10. Base-T Options
X : Two

11. BaseX Media Options

12. Gigabit Ethernet Still under development
Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path
Uses optical fiber over short distances
1-gbps switching hub provides backbone connectivity

13. Gigabit Ethernet Media Options

14. Example 100-Mbps Ethernet Backbone Strategy

15. Example Gigabit Ethernet Backbone Strategy

16. Token Ring LANs (802.5): Medium Access Control
Based on the use of a small frame, called a token, that circulated when all stations are idle.
Token “seized” by changing a bit on the circulating frame to indicate start of frame rather than token
Default configuration requires sender to complete transmission and begin receiving transmitted frame before releasing the token
“Early token release” allows release of token after transmission but before receipt of frame

18. 802.5 Transmission Media
Original specified shielded twisted pair with data rates of 4 and 16mbps
New addition to standard allows use of UTP for 4mbps
Utilizes differential Manchester encoding
1997 update to IEEE introduced dedicated token ring (DTR).

19. Fibre Channel
combine the best features of channel and protocol-based technologies
the simplicity and speed of channel communications
the flexibility and inter-connectivity that characterize protocol-based network communications.
more like a traditional circuit-switched or packet-switched network, in contrast to the typical shared-medium LAN

20. Fibre Channel Network

21. Fibre Channel Goals Full-duplex links with two fibers per link
Performance from 100 Mbps to 800 Mbps on a single link (200 Mbps to1600 Mbps per link)
Support for distances up to 10 km
Small connectors
High-capacity utilization with distance insensitivity
Greater connectivity than existing multidrop channels
Broad availability (i.e., standard components)
Support for multiple cost/performance levels, from small systems to supercomputers
Ability to carry multiple existing interface command sets for existing channel and network protocols

22. Fibre Channel Elements
Nodes
The end systems
Includes one or more N_ ports for interconnection
Fabric
Collection of switching elements s between systems
Each element includes multiple F_ ports
Responsible for buffering and for routing frames between source and destination nodes

23. Fibre Channel Protocol Architecture
FC-0 Physical Media: Includes optical fiber, coaxial cable, and shielded twisted pair, based on distance requirements
FC-1 Transmission Protocol: Defines the signal encoding scheme
FC-2 Framing Protocol: Defines topologies, frame format, flow/error control, and grouping of frames
FC-3 Common Services: Includes multicasting
FC-4 Mapping: Defines the mapping of various channel and network protocols to Fibre Channel

24. Wireless LANS LAN extension Cross-building interconnect Nomadic access
Wireless network connected to a main wire-based network
Cross-building interconnect
Point-to-point link between networks in separate buildings
Nomadic access
Wireless link between a LAN hub and a mobile data terminal
Ad hoc networks
a peer-to-peer network (no centralized server) set up temporarily to meet some immediate need.

25. Single-Cell Wireless LAN Configuration
CM: Control Module (Access Point)

26. Multiple-Cell Wireless LAN Configuration

27. Infrastructure Wireless LAN
Ad Hoc LAN

28. Wireless LAN Requirements
Throughput
Number of nodes:
Connection to backbone LAN
Service area
Battery power consumption
Transmission robustness and security
Co-located network operation
License-free operation
Handoff/roaming
Dynamic configuration

29. IEEE 802.11 Standards Association/Re-Association/Disassociation
Authentication
Privacy
Physical Media
Infrared at 1 or 2 Mbps at a wavelength of nm
Direct-sequence spread spectrum in the 2.4-GHz ISM band (DSSS)
Frequency-hopping spread spectrum in the 2.4-GHz ISM band, at data rates of 1 and 2 Mbps. (FHSS)

30. Wireless LAN Standards

31. Discrete Sequence Spread Spectrum

32. Frequency-Hopping Spread Spectrum

33. ISM Band ISM stands for Instrumentation, Scientific, and Medical.
An unlicensed publicly owned part of the radio spectrum in the 900MHz, 2.4GHz and 5GHz ranges.

34. Hidden Terminal ※ C cannot hear from A.B
※ C cannot hear from A.
 Collision at B cannot be detected by A and C.

35. IEEE MAC - CSMA/CA
Carrier Sense Multiple Access / Collision Avoidance
Listen before talk. If the medium is busy, the transmitter backs off for a random period.
Send a short message: Ready to send (RTS), including dest. address and duration of transmission.
Destination sends: Clear to send (CTS)
Send data.
Receive acknowledgement.

36. 4-Way Handshake