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

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

High-Speed LANs

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)

IEEE 802.3 Frame Format Preamble: 10101010… SFD: Start of Frame Delimiter (10101011) DA: Destination Address SA: Source Address FCS: Frame Check Sequence (32-bit CRC) MAC Address (Physical Address)

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: http://www.cavebear.com/CaveBear/Ethernet/

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

802.3 10BaseX Media Options

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

802.3 100Base-T Options X : Two

802.3 100BaseX Media Options

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

Gigabit Ethernet Media Options

Example 100-Mbps Ethernet Backbone Strategy

Example Gigabit Ethernet Backbone Strategy

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

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 802.5 introduced dedicated token ring (DTR).

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

Fibre Channel Network

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

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

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

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.

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

Multiple-Cell Wireless LAN Configuration

Infrastructure Wireless LAN Ad Hoc LAN

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

IEEE 802.11 Standards Association/Re-Association/Disassociation Authentication Privacy Physical Media Infrared at 1 or 2 Mbps at a wavelength of 850-950 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)

Wireless LAN Standards http://www.networkmagazine.com/article/NMG20020206S0006/2

Discrete Sequence Spread Spectrum

Frequency-Hopping Spread Spectrum

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.

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

IEEE 802.11 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.

4-Way Handshake

http://www.seattlewireless.net/