Recap
                   Lecture 03:
                   Networking                                 Architecture, what? and...
LAN example: the old SoCS                                                                                                 ...
Switching schemes                                                                                             Protocol
 Br...
Routing example                                                                              Routing tables
 Routings from...
Exercises:
will be included in the next lecture




                       Lecture 03      25




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Lecture03 H

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Lecture03 H

  1. 1. Recap Lecture 03: Networking Architecture, what? and why? Tiered Architecture Various software layer: middleware client/server Architecture Multiple servers, Proxy servers, Peer Distributed Systems processes Behzad Bordbar Design requirements of DS: Performance, School of Computer Science, University of Birmingham, UK QoS, Dependability Lecture 03 1 Lecture 03 2 Overview of the lecture Requirements of Networks design and implementation Requirements for networks performance Various types of networks Scalability How does it work? network principles Reliability Mode of transformation Security Protocols, what is a protocol? Mobility OSI Multicast Routing and RIP Lecture 03 3 Lecture 03 4 Types of Networks LAN messages are carried in high speed between connected PAN (Personal Area Network) nodes by a single communication medium LANs (Local Area Networks) Suitable for home office ,… radius of 1-2 km WANs (Wide Area Networks) • High bandwidth 10-1000Mbps (total amount of data MANs (Metropolitan Area Networks) per unit of time) • Low latency 1-10 ms (time taken for a bit to reach WPAN (Wireless PAN) destination) WLAN (Wireless LAN) Technology: predominantly Ethernet WMAN (Wireless MAN) WWAN (Wireless WAN) Lecture 03 5 Lecture 03 6 1
  2. 2. LAN example: the old SoCS WAN Campus router subn et router/ firewall Covers Worldwide, Staff subnet Student subnet compute servers perky pinky file server/ Low bandwidth 0.01-600 Mbps, Eswitch Eswitch Data gateway wallace printers high latency (100-500 ms) tinky-winky gromit other Satellite/wire/cable, use of routers which also file server Data servers laa-laa introduce delays casper web server felix po MAN hub hub Wire/cable, uses Digital Subscriber Line (DSL) and cable desktop computers The Simpsons The Muppets modem 10 Mbps Ethernet 100 Mbps Ethernet Range of technologies (ATM, Ethernet) Eswitch: Ethernet switch Lecture 03 7 Lecture 03 8 Wireless networks Network comparison WLANs (Wireless Local Area Networks) to replace wired LANs Range Bandwidth (Mbps) Latency (ms) LAN 1-2 kms 10-1000 1-10 WaveLAN technology (IEEE 802.11) WAN worldwide 0.010-600 100-500 WPANs (Wireless Personal Area Networks) MAN 2-50 kms 1-150 10 Wireless LAN 0.15-1.5 km 2-11 5-20 variety of technologies Wireless WAN worldwide 0.010-2 100-500 Internet worldwide 0.5-600 100-500 GSM, infra-red, BlueTooth low-power radio WAP (Wireless Applications Protocol) Lecture 03 9 Lecture 03 10 Network principles Mode of transmission Mode of transmission Packet Transmission Switching schemes messages divided into packets. Example: 01101110 Protocol suites packets queued in buffers before sent onto link Routing QoS not guaranteed Congestion control Data streaming links guarantee QoS (rate of delivery) for multimedia traffic higher bandwidth Lecture 03 11 Lecture 03 12 2
  3. 3. Switching schemes Protocol Broadcasts (Ethernet, wireless) well-known set of rules and formats to be used for send messages to all nodes communication between processes to perform a nodes listen for own messages (carrier sensing) given task Circuit switching (phone networks) Packet switching (TCP/IP) Two parts: store-and-forward specification of sequence of messagegs that unpredictable delays must be exchanged Frame/cell relay (ATM) bandwith & latency guaranteed (virtual path) specification of the format of the data in each small, fixed size packets (padded if necessary) message avoids error checking at nodes (use reliable links) Lecture 03 13 Lecture 03 14 Protocols (OSI view) Message encapsulation HTTP, FTP, ... Message sent Message received External data representation., encryption Application-layer message Layer n Failure detection and recovery Presentation header TCP, UDP Session header Layer 2 IP, ATM Transport header Layer 1 Sender Communication Recipient Network header medium Definition: set of rules and formats for exchanging data, arranged into layers called protocol suite/stack. Headers appended/unpacked by each layer. Lecture 03 15 Lecture 03 16 OSI protocol summary Routing Layer Description Example Necessary in non-broadcast networks (cf Internet) Application Protocols for specific applications. HTTP, FTP, Distance-vector algorithm: each node SMTP Presentation Protocols for independent data representation and Secure Sockets, stores table of state & cost info of links, cost infinity for encryption if required. CORBA CDR faulty links Session Protocols for failure detection and recovery. determines route taken by packet (the next hop) Transport Message-level communication between ports TCP, UDP attached to processes. Connection-oriented or periodically updates the table and sends to neighbours connectionless. may converge slowly [Bellman-Ford] Network Packet-level transmission on a given network. IP, ATM Requires routing in WANs and Internet. RIP-1 for Internet similar except Data link Packet-level transmission between nodes connected Ethernet MAC, use default routes, plus multicast and authentication by a physical link. ATM cell transfer better convergence Physical transmit sequence of binary data using Signalling, various mediums ISDN Lecture 03 17 Lecture 03 18 3
  4. 4. Routing example Routing tables Routings from A Routings from B To Link Cost To Link Cost A local 0 A 1 1 B local 0 Routings from A Routings from B Routings from C B 1 1 C 1 2 C 2 1 To Link Cost To Link Cost To Link Cost D 3 1 D 1 2 A local 0 A 1 1 A 2 2 E 1 2 E 4 1 B 1 1 B local 0 B 2 1 A 1 B C 1 2 C 2 1 C local 0 2 D 3 1 D 1 2 D 5 2 Hosts E 1 2 E 4 1 E 5 1 3 Links 4 or local C networks 5 D 6 E Routings from D Routings from E To Link Cost To Link Cost Routers A 3 1 A 4 2 B 3 2 B 4 1 C 6 2 C 5 1 D local 0 D 6 1 E 6 1 E local 0 Lecture 03 19 Lecture 03 20 RIP routing algorithm RIP routing algorithm Variables: Tl local table, Tr table received. Send: Each t seconds or when Tl changes, send Tl on each non-faulty Update: Each 30 seconds or when local table changes, send outgoing link. update 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) { Propagation:When router X finds that router Y has a Rr.cost = Rr.cost + 1; shorter and faster path to router Z, then it will update its Rr.link = n; local table to indicate this fact. Any faster path is quickly if (Rr.destination is not in Tl) add Rr to Tl; propagated to neighbouring rotes through the Update // add new destination to Tl else for all rows Rl in Tl { process. if (Rr.destination = Rl.destination and (Rr.cost < Rl.cost or Rl.link = n)) Rl = Rr; Shown to converge by mathematicians (Bertsekas). // Rr.cost < Rl.cost : remote node has better route See next slide for details. // Rl.link = n : remote node is more authoritative } } Lecture 03 21 } Lecture 03 22 Sample routes Summary Send from C to A: Various types of Networks (LAN, WAN, …) to link 2, arrive at B to link 1, arrive at A Switching Schemes Send from C to A if B table OSI layers and protocol modified to: Routing and RIP algorithm to link 5, arrive at E Routings from C to link 4, arrive at B To Link Cost to link 1, arrive at A B 2 1 Further reading: page 65-96 NB extra hop. C local 0 E 5 1 default 5 - Lecture 03 23 Lecture 03 24 4
  5. 5. Exercises: will be included in the next lecture Lecture 03 25 5

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