1CSE 123bCSE 123bGraduate NetworkingGraduate NetworkingSpring 2004Spring 2004Last Lecture: PotpourriLast Lecture: PotpourriStefan SavageStefan SavageJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriFinalFinalz Check Studentlink to be sure, but I believe that its Wed Jan 9th11:30-2:30 in this room.z Closed bookz You can bring on 8.5x11 sheet of paper and you can do just about anything to that piece of paper you want (i.e. write on both sides, print on it, etc)◆ You can’t tape your textbook to the sheet of paper though◆ Or your laptopz Same style as midterm◆ FYI: You may be asked questions about projectz Will cover entire classJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriReview sessionReview sessionz Still working on getting a roomz Most likely on Monday at 4-5pmz I’ll post details on the Webboard as soon as I know for sureJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriStuff we can look at todayStuff we can look at todayz Options◆ Skim IPv6◆ Some multimedia + VOIP◆ Example of Network measurement tricks◆ How high-speed routers are designedJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriIPv6IPv6z Originally motivated by crisis in IP address space◆ 32 bits not enough if everything gets an IP address◆ Subnetting and CIDR helped alot, but not a long-term solution (mobile phones)z Solution: Increase the size of IP addresses◆ Originally to 64, then to 128 bits◆ Requires changes to IP headerz If we’re going to change the header, might as well change other aspects of IPz Rule of thumb: IPv6 = IPv4 + big addresses + IPSEC, Mobile IP + DHCP + ARP + improvements to theseJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriIPv6 (2)IPv6 (2)z IP addresses are 128 bits◆ Unicast, multicast, local, etc.◆ 1234:ABCD:1234:ABCD:1234:ABCD:1234:ABCD◆ Registry, provider, subscriber, subnetwork, interface◆ Interface ID used as lowest 6 bytesz Simplified headers◆ 40 bytes (20 for IPv4)◆ Use header extensions for optionsz Autoconfiguration◆ Multiple addresses per host (link-local address)z FlowLabel, priority, security, mobility2June 3, 2004 CSE 123b -- Lecture 17 – PotpourriIPv6 and IPv4 InteroperabilityIPv6 and IPv4 Interoperabilityz Dual-stack operation◆ IPv6 nodes that support both IPv4 and IPv6z Tunneling ◆ IPv6 packets encapsulated within IPv4 packets◆ End-points speak IPv6, but use IPv4 packet to use standard Internet routing◆ Easy mapping if IPv6 embeds IPv4 address, otherwise need to configure a tableJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriMultimedia & IP TelephonyMultimedia & IP Telephonyz Two sets of issuesz How much does the network help in making these applications possible?z How does the application participate?June 3, 2004 CSE 123b -- Lecture 17 – Potpourriz Audio/video is a real-time service in the sense that data must be received by a deadline to be usefulz Real-time apps need assurances from the networkz Q: What assurances does playback require? VOIP?MicrophoneSpeakerSampler,A D converterBuffer,D ANetwork requirementsNetwork requirementsVariable bandwidth and delay (jitter)InternetJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriNetwork Support for PlaybackNetwork Support for Playbackz Bandwidth◆ There must be enough on average◆ But we can tolerate to short term fluctuationsz Delay◆ Ideally it would be fixed◆ But we can tolerate some variation (jitter)z Loss◆ Ideally there would be none◆ But we can tolerate some lossesJune 3, 2004 CSE 123b -- Lecture 17 – Potpourri123Packets (%)90% 97% 98% 99%150 20010050Delay (milliseconds)Example: Delay and JitterExample: Delay and JitterJune 3, 2004 CSE 123b -- Lecture 17 – Potpourriz Buffer before playout so that most late samples will have arrivedSequence numberPacketgenerationNetworkdelayBufferPlaybackTimePacketarrivalTolerating Jitter with Tolerating Jitter with BufferingBuffering3June 3, 2004 CSE 123b -- Lecture 17 – PotpourriApplication requirementsApplication requirementsz Application variations ◆ Rigid – fixed playback point (low jitter)◆ Adaptive – application can vary playback point (jitter ok)◆ Tolerant – can tolerate interrupt/degradation◆ Intolerant – can’tz In reality only two classes◆ Rigid and intolerant applications (e.g. telemedicine, perhaps ip telephony)◆ Adaptive and tolerant (e.g. RealPlayer)June 3, 2004 CSE 123b -- Lecture 17 – PotpourriHow can network provide How can network provide guarantees?guarantees?z Default Internet -> best effortz Two new service models◆ Integrated Services» Multiple service classes with explicit service specification per flow» “I need 500kbps, with a maximum delay of 50ms no more variation than 5ms”» Applications explicitly reserve capacity along path to destination (RSVP protocol)» Lots of state, but precise guarantees◆ Differentiated services» Multiple service classes» “I need my voice packets to be put in the platinum class of service”» Packets are marked to indicate what class they should be in» More scalable, but not guaranteed servicez In all cases routers scheduling modified (no longer FIFO)z Neither widely deployed for general useJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriToken BucketsToken Bucketsz Common, simple descriptorz Use tokens to send bitsz Average bandwidth is R bpsz Maximum burst is B bitsFill rate R tokens/secBucket sizeB tokensSendingdrainstokensJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriUsing Token bucket Using Token bucket traffic conditioningtraffic conditioningz Operation◆ Token bucket size: b (maximum number of tokens)◆ Token bucket rate: r (rate at which new tokens are provided)z Need k tokens to send a packet of k bytesz Applications◆ Shaping (delay packets until k tokens appear)» Long term rate is limited to r, short term bursts to b» Over some interval T, traffic is limited to b+r*T◆ Policing (drop packets if insufficient tokens)◆ Buffer management (mark packets and transmit if > k)» Drop marked (i.e. out-of-spec) packets during congestionJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriToken Bucket OperationToken Bucket OperationTokensPacketOverflowTokens TokensPacketEnough tokens Æpacket goes through,tokens removedNot enough tokens Æ wait for tokens to accumulate, drop or mark packetJune 3, 2004 CSE 123b -- Lecture 17 – PotpourriMultimedia protocolsMultimedia protocolsz Data transport◆ RTP (Real-time protocol)» UDP-based protocol that carries encoded data, specifies the encoding, provide time