SIPSIP ServicesSetting up a call to a known IP addressSetting up a call (more)Example of SIP messageName translation and user locataionSIP RegistrarSIP ProxyExampleComparison with H.323Improving QOS in IP NetworksPrinciples for QOS GuaranteesPrinciples for QOS Guarantees (more)Slide 14Slide 15Summary of QoS PrinciplesScheduling And Policing MechanismsNeed for a Scheduling DisciplineFIFO SchedulingRequirementsMax-Min Fair ShareSchedulable RegionDesigning a scheduling disciplinePriority SchedulingSlide 25Round Robin SchedulingWeighted Fair QueueingPolicing MechanismsTraffic RegulatorsSlide 30Policing Mechanisms (more)IETF Integrated ServicesIntserv: QoS guarantee scenarioRSVPCall AdmissionIntserv QoS: Service models [rfc2211, rfc 2212]Chapter 6 outlineIETF Differentiated ServicesDiffserv ArchitectureSlide 40Classification and ConditioningSlide 42Forwarding (PHB)Slide 44Multimedia Networking: SummarySIPSession Initiation ProtocolComes from IETFSIP long-term visionAll telephone calls and video conference calls take place over the InternetPeople are identified by names or e-mail addresses, rather than by phone numbers.You can reach the callee, no matter where the callee roams, no matter what IP device the callee is currently using.SIP ServicesSetting up a callProvides mechanisms for caller to let callee know she wants to establish a callProvides mechanisms so that caller and callee can agree on media type and encoding.Provides mechanisms to end call.Determine current IP address of callee.Maps mnemonic identifier to current IP addressCall managementAdd new media streams during callChange encoding during callInvite others Transfer and hold callsSetting up a call to a known IP address• Alice’s SIP invite message indicates her port number & IP address. Indicates encoding that Alice prefers to receive (PCM ulaw)• Bob’s 200 OK message indicates his port number, IP address & preferred encoding (GSM)• SIP messages can be sent over TCP or UDP; here sent over RTP/UDP. •Default SIP port number is 5060.t i m e t i m eB o b ' st e r m i n a l r i n g sA l i c e1 6 7 . 1 8 0 . 1 1 2 . 2 4B o b1 9 3 . 6 4 . 2 1 0 . 8 9p o r t 3 8 0 6 0L a w a u d i oG S Mp o r t 4 8 7 5 3Setting up a call (more)Codec negotiation:Suppose Bob doesn’t have PCM ulaw encoder. Bob will instead reply with 606 Not Acceptable Reply and list encoders he can use. Alice can then send a new INVITE message, advertising an appropriate encoder.Rejecting the callBob can reject with replies “busy,” “gone,” “payment required,” “forbidden”.Media can be sent over RTP or some other protocol.Example of SIP messageINVITE sip:[email protected] SIP/2.0Via: SIP/2.0/UDP 167.180.112.24From: sip:[email protected]: sip:[email protected] Call-ID: [email protected]: application/sdpContent-Length: 885c=IN IP4 167.180.112.24m=audio 38060 RTP/AVP 0Notes:HTTP message syntaxsdp = session description protocolCall-ID is unique for every call.• Here we don’t know Bob’s IP address. Intermediate SIPservers will be necessary. • Alice sends and receives SIP messages using the SIP default port number 506. • Alice specifies in Via:header that SIP client sends and receives SIP messages over UDPName translation and user locataionCaller wants to call callee, but only has callee’s name or e-mail address.Need to get IP address of callee’s current host:user moves aroundDHCP protocoluser has different IP devices (PC, PDA, car device)Result can be based on: time of day (work, home)caller (don’t want boss to call you at home)status of callee (calls sent to voicemail when callee is already talking to someone)Service provided by SIP servers:SIP registrar serverSIP proxy serverSIP RegistrarREGISTER sip:domain.com SIP/2.0Via: SIP/2.0/UDP 193.64.210.89 From: sip:[email protected]: sip:[email protected]: 3600When Bob starts SIP client, client sends SIP REGISTER message to Bob’s registrar server (similar function needed by Instant Messaging)Register Message:SIP ProxyAlice send’s invite message to her proxy servercontains address sip:[email protected]Proxy responsible for routing SIP messages to calleepossibly through multiple proxies.Callee sends response back through the same set of proxies.Proxy returns SIP response message to Alice contains Bob’s IP addressNote: proxy is analogous to local DNS serverExampleCaller [email protected] with places a call to [email protected] (1) Jim sends INVITEmessage to umass SIPproxy. (2) Proxy forwardsrequest to upenn registrar server. (3) upenn server returnsredirect response,indicating that it should try [email protected](4) umass proxy sends INVITE to eurecom registrar. (5) eurecom regristrar forwards INVITE to 197.87.54.21, which is running keith’s SIP client. (6-8) SIP response sent back (9) media sent directly between clients. Note: also a SIP ack message, which is not shown.S I P c l i e n t2 1 7 . 1 2 3 . 5 6 . 8 9S I P c l i e n t1 9 7 . 8 7 . 5 4 . 2 1S I P p r o x yu m a s s . e d uS I P r e g i s t r a ru p e n n . e d uS I Pr e g i s t r a re u r e c o m . f r123456789Comparison with H.323H.323 is another signaling protocol for real-time, interactiveH.323 is a complete, vertically integrated suite of protocols for multimedia conferencing: signaling, registration, admission control, transport and codecs.SIP is a single component. Works with RTP, but does not mandate it. Can be combined with other protocols and services.H.323 comes from the ITU (telephony).SIP comes from IETF: Borrows much of its concepts from HTTP. SIP has a Web flavor, whereas H.323 has a telephony flavor. SIP uses the KISS principle: Keep it simple stupid.Improving QOS in IP NetworksThus far: “making the best of best effort”Future: next generation Internet with QoS guaranteesRSVP: signaling for resource reservationsDifferentiated Services: differential guaranteesIntegrated Services: firm guaranteessimple model for sharing and congestion studies:Principles for QOS GuaranteesExample: 1MbpsI P phone, FTP share 1.5 Mbps link. bursts of FTP can congest router, cause audio losswant to give priority to audio over FTPpacket marking needed for router to distinguish between different classes; and new router policy to treat packets accordinglyPrinciple 1Principles for QOS Guarantees (more)what if
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