Slides for Chapter 3: Networking and Internetworking From Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edition 4, © Pearson Education 2005

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Networking Issues (1) z Performance: yLatency (time between send and start to receive) yData transfer rate (bits per second) yTransmission time = latency + length / transfer rate ySystem bandwidth, throughput: total volume of traffic in a given amount of time yUsing different channels concurrently can make bandwidth > data transfer rate ytraffic load can make bandwidth < data transfer rate ynetwork speed < memory speed (about 1000 times) ynetwork speed > disk speed (high-speed network file servers can beat local disks)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Networking Issues (2) z scalability z reliability y corruption is rare ymechanisms in higher-layers to recover errors yerrors are usually timing failures, the receiver doesn't have resources to handle the messages z security yfirewall on gateways (entry point to org's intranet) yencryption is usually in higher-layers zmobility--communication is more challenging: locating, routing,... zquality of service--real-time services zmulticasting--one-to-many communication

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (1) zLocal Area Networks (LAN) yfloor/building-wide ysingle communication medium yno routing, broadcast ysegments connected by switches or hubs yhigh bandwidth, low latency yEthernet - 10Mbps, 100Mbps, 1Gbps yno latency guarantees (what could be the consequences?) yPersonal area networks (PAN) [ad-hoc networks]: blue tooth, infra-red for PDAs, cell phones, …

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (2) zMetropolitan Area Networks (MAN) ycity-wide, up to 50 km yDigital Subscriber Line (DSL): Mbps, 5.5km from switch yCable modem: 1.5 Mbps, longer range than DSL

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (3) zWide Area Networks (WAN) yworld-wide yDifferent organizations yLarge distances yrouted, latency seconds y1-10 Mbps (upto 600 Mbps)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (4) zWireless local area networks (WLAN) yIEEE (WiFi) y Mbps, 1.5km x (1997): upto 2 Mbps, 2.4 GHz x a (1999): upto 54 Mbps, 5 GHz, 60 feet x b (1999): upto 11 Mbps, 2.4 GHz, 300 feet [most popular] x g (2003): upto 54 Mbps, 2.4 GHz [backward compatible with b, becoming more popular] zWireless metropolitan area networks (WMAN) yIEEE (WiMax) y Mbps, 5-50km

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (5) zWireless wide area networks (WWAN) yworldwide yGSM (Global System for Mobile communications) y9.6 – 33 kbps y3G (“third generation”): kbps to 2Mbps

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Types of Networks (6) zInternetworks yconnecting different kinds of networks yrouters, gateways

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network performance ExampleRangeBandwidth (Mbps) Latency (ms) Wired: LANEthernet1-2 km MANATM250 km WANIP routingworldwide InternetworkInternetworldwide Wireless: WPANBluetooth ( ) m WLANWiFi (IEEE ) km WMANWiMAX (802.16)550 km WWAN GSM, 3G phone netsworldwide

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (1) zPacket transmission ymessage: logical unit of informatio ypacket: transmission unit yrestricted length: sufficient buffer storage, reduce hogging

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (2) zData Streaming yaudio/video yNeed 120 Mbps (1.5 Mbps compressed) yplay time: the time when a frame need to be displayed yfor example, 24 frames per second, frame 48 must be display after two seconds yIP protocol provides no guaranteesIPv6 (new) includes features for real-time streams, stream data are treated separately yResource Reservation Protocol (RSVP), Real-time Transport Protocol (RTP)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (3) zSwitching schemes (transmission between aribitrary nodes) yBroadcast: ethernet, token ring, wireless yCircuit switching: wires are connected yPacket switching: xstore-and-forward xdifferent routes x“store-and-forward” needs to buffer the entire packet before forwarding yFrame relay xSmall packets xLooks only at the first few bits xDon’t buffer/store the entire frame

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (4) zProtocols yKey components xSequence of messages xFormat of messages

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (5) zProtocol layers, why? Layer n Layer 2 Layer 1 Message sent Message received Communication medium SenderRecipient

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (6) zEncapsulation in layered protocols

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (7) zISO Open Systems Interconnection (OSI) model

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (8) yInternet layers xApplication = application + presentation xTransport = transport + session

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (9) zPacket assembly yheader and data ymaximum transfer unit (MTU): 1500 for Ethernet y64K for IP (8K is common because of node storage) zports: destination abstraction (application/service protocol) zaddressing: transport address = network address + port yWell-known ports (below 1023) yRegistered ports ( ) yPrivate (up to 65535)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (10) zPacket delivery (at the network layer) y Datagram packet xone-shot, no initial set up xdifferent routes, out of order xEthernet, IP y Virtual circuit packet xinitial set up for resources xvirtual circuit # for addressing xATM zSimilar but different pairs of protocols at the transport layer (connection-oriented and connectionless)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (11) zRouting yLAN? yRouting Algorithm xdecide which out-going link to forward the packet for circuit switching, the route is determined during the circuit setup time for packet switching, each packet is routed independently xupdate state of the out-going links yRouting Table x fields: link, cost (e.g. hop count) x a record for each destination

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (12) zRouter example Hosts Links or local networks A DE B C Routers

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (13): Routing tables Routings from DRoutings from E ToLinkCostToLinkCost A B C D E local A B C D E Routings from ARoutings from BRoutings from C ToLinkCostToLinkCostToLinkCost A B C D E local A B C D E A B C D E

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (14) zRouter information protocol (RIP) y"Bellman-Ford distance vector" algorithm ySender: send table summary periodically (30s) or changes to neighbors yReceiver: update the table on new destinations, lower cost routes, changes in cost xdoes the remote table has a better route? xremote note is more authoritative (has more up-to-date info)? xwhen a link is faulty, set cost to infinity yRIP-1 (RFC 1058) yMore recent algorithms xmore information, not just neighbors xlink-state algorithms, each node responsible for finding the optimum routes

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 4 © Pearson Education 2005 Network principles (15): Pseudocode for RIP routing algorithm zTl is the table local table; Tr is the received remote table Send: Each t seconds or when Tl changes, send Tl on each non-faulty outgoing link. Receive: Whenever a routing table Tr is received on link n: for all rows Rr in Tr { if (Rr.link != n) { Rr.cost = Rr.cost + 1; Rr.link = n; if (Rr.destination is not in Tl) add Rr to Tl; // add new destination to Tl else for all rows Rl in Tl { if (Rr.destination = Rl.destination and (Rr.cost < Rl.cost or Rl.link = n)) Rl = Rr; // Rr.cost < Rl.cost : remote node has better route // Rl.link = n : remote node is more authoritative }