High Speed LANs 3BA33 David Lewis 2 nd Semester 2006-07 3BA33 D.Lewis 2007 1 Characteristics of High Speed LANS 3BA33 D.Lewis 2007 3 Introduction Fast Ethernet and Gigabit Ethernet Fibre Channel High-speed Wireless LANs Text ch. 6, High-Speed Networks and Internets, 2 nd Ed, William Stallings 3BA33 D.Lewis 2007 2 Emergence of High-Speed LANs 2 Significant trends Computing power of PCs continues to grow rapidly Network computing Examples of requirements Centralized server farms Power workgroups High-speed local backbone 3BA33 D.Lewis 2007 4
Classical Ethernet Bus topology LAN 10 Mbps CSMA/CD medium access control protocol 2 problems: A transmission from any station can be received by all stations How to regulate transmission 3BA33 D.Lewis 2007 5 Ethernet Bus 3BA33 D.Lewis 2007 7 Solution to First Problem Data transmitted in blocks called frames: User data Frame header containing unique address of destination station 3BA33 D.Lewis 2007 6 CSMA/CD Carrier Sense Multiple Access/ Carrier Detection 1. If the medium is idle, transmit. 2. If the medium is busy, continue to listen until the channel is idle, then transmit immediately. 3. If a collision is detected during transmission, immediately cease transmitting. 4. After a collision, wait a random amount of time, then attempt to transmit again (repeat from step 1). 3BA33 D.Lewis 2007 8
CSMA/CD Operation T0 A transmits T1 B&C ready to transmit B senses and defers, C proceeds T2 C detect collision and desists T3 A detects collision and desists 3BA33 D.Lewis 2007 9 Medium Options at 10Mbps Naming scheme <data rate in Mbps> <signaling method> <max length 100 metres> 10Base5 10 Mbps 50-ohm coaxial cable bus Maximum segment length 500 meters 10Base-T Twisted pair, maximum length 100 meters Star topology (hub or multipoint repeater at central point) 3BA33 D.Lewis 2007 11 Frame Format 3BA33 D.Lewis 2007 10 Hubs 3BA33 D.Lewis 2007 12
Hubs and Switches Hub Transmission from a station received by central hub and retransmitted on all outgoing lines Only one transmission at a time Star wiring bus operation Layer 2 Switch Incoming frame switched to one outgoing line Many transmissions at same time 3BA33 D.Lewis 2007 13 Bridge Frame handling done in software Analyze and forward one frame at a time Store-and-forward Layer 2 Switch Frame handling done in hardware Multiple data paths and can handle multiple frames at a time Can do faster cutthrough switching 3BA33 D.Lewis 2007 15 Hub Use existing wiring Isolate faulty hosts Same capacity as bus L2 Switch Full capacity per link Analyze and forward one frame at a time Store-and-forward 3BA33 D.Lewis 2007 14 Layer 2 Switches Flat address space Broadcast storm Only one path between any 2 devices Solution 1: subnetworks connected by routers Solution 2: layer 3 switching, packetforwarding logic in hardware 3BA33 D.Lewis 2007 16
Typical configuration Divide into L3 subnets Fast backbone Regular s/w router to WAN Figure 6.6 3BA33 D.Lewis 2007 17 Figure 6.8 3BA33 D.Lewis 2007 19 Fast Ethernet Options 3BA33 D.Lewis 2007 18 Gigabit Ethernet Configuration Extend fast ether Smooth migration Skills Management software Topologies New media and transmission specs 3BA33 D.Lewis 2007 20
Gigabit Ethernet Media Options 3BA33 D.Lewis 2007 21 MAN: Benefits of 10 Gbps Ethernet over ATM No expensive, bandwidth consuming conversion between Ethernet packets and ATM cells Network is Ethernet, end to end IP plus Ethernet offers QoS and traffic policing capabilities approaching those of ATM Wide variety of standard optical interfaces for 10 Gbps Ethernet 3BA33 D.Lewis 2007 23 Ethernet Data Rate and Distance Summary 3BA33 D.Lewis 2007 22 Fibre Channel 2 methods of communication with processor: I/O channel Network communications Fibre channel combines both Simplicity and speed of channel communications Flexibility and interconnectivity of network communications 3BA33 D.Lewis 2007 24
Figure 6.12 3BA33 D.Lewis 2007 25 Fibre Channel Network-Oriented Facilities Full multiplexing between multiple destinations Peer-to-peer connectivity between any pair of ports Internetworking with other connection technologies 3BA33 D.Lewis 2007 27 I/O channel Hardware based, high-speed, short distance Direct point-to-point or multipoint communications link Data type qualifiers for routing payload Link-level constructs for individual I/O operations Protocol specific specifications to support e.g. SCSI 3BA33 D.Lewis 2007 26 Fibre Channel Requirements Full duplex links with 2 fibres/link 100 Mbps 800 Mbps Distances up to 10 km Small connectors high-capacity Greater connectivity than existing multidrop channels Broad availability Support for multiple cost/performance levels Support for multiple existing interface command sets 3BA33 D.Lewis 2007 28
Figure 6.13 3BA33 D.Lewis 2007 29 Wireless LAN Requirements Throughput Number of nodes Connection to backbone Service area Battery power consumption Transmission robustness and security Collocated network operation License-free operation Handoff/roaming Dynamic configuration 3BA33 D.Lewis 2007 31 Fibre Channel Protocol Architecture FC-0 Physical Media FC-1 Transmission Protocol FC-2 Framing Protocol FC-3 Common Services FC-4 Mapping 3BA33 D.Lewis 2007 30 Comparison: infrastructure vs. ad-hoc networks infrastructure network AP AP: Access Point AP wired network AP ad-hoc network 3BA33 D.Lewis 2007 32
STA 1 ESS Architecture of an infrastructure network 802.11 LAN BSS 1 Access Point BSS 2 Portal Distribution System Access Point 802.x LAN Station (STA) terminal with access mechanisms to the wireless medium and radio contact to the access point Basic Service Set (BSS) group of stations using the same radio frequency Access Point station integrated into the wireless LAN and the distribution system Portal bridge to other (wired) networks Distribution System interconnection network to form one logical network (EES: Extended Service Set) based on several BSS STA 2 802.11 LAN STA 3 3BA33 D.Lewis 2007 33 IEEE standard 802.11 mobile terminal fixed terminal infrastructure network application access point application TCP TCP IP IP LLC LLC LLC 802.11 MAC 802.11 MAC 802.3 MAC 802.3 MAC 802.11 PHY 802.11 PHY 802.3 PHY 802.3 PHY 3BA33 D.Lewis 2007 35 Architecture of an ad-hoc network STA 1 802.11 LAN IBSS 1 STA 2 STA 3 Direct communication within a limited range Station (STA): terminal with access mechanisms to the wireless medium Independent Basic Service Set (IBSS): group of stations using the same radio frequency IBSS 2 STA 5 STA 4 802.11 LAN 3BA33 D.Lewis 2007 34 IEEE 802.11 Services Association Reassociation Disassociation Authentication Privacy 3BA33 D.Lewis 2007 36
Figure 6.16 3BA33 D.Lewis 2007 37