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Klara Nahrstedt Spring 2010

CS 414 – Multimedia Systems Design Lecture 22 – Multimedia Extensions to Existing TCP/IP Protocols. Klara Nahrstedt Spring 2010. Administrative. MP3 posted on March 15, Deadline Monday, April 12 Demonstration 5-7pm in 216 SC. Outline. Multimedia Transport Extensions(Layer 4)

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Klara Nahrstedt Spring 2010

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  1. CS 414 – Multimedia Systems DesignLecture 22 – Multimedia Extensions to Existing TCP/IP Protocols Klara Nahrstedt Spring 2010 CS 414 - Spring 2010

  2. Administrative • MP3 posted on March 15, • Deadline Monday, April 12 • Demonstration 5-7pm in 216 SC CS 414 - Spring 2010

  3. Outline • Multimedia Transport Extensions(Layer 4) • Multimedia IP Extensions (Layer 3) CS 414 - Spring 2010

  4. Internet Multimedia Protocol Stack Media encaps (H.264, MPEG-4) APPLICATION RTSP RSVP RTCP Layer 5 (Session) SIP RTP Layer 4 (Transport) TCP UDP KERNEL Layer 3 (Network) IP Version 4, IP Version 6 AAL3/4 AAL5 MPLS Layer 2 (Link/MAC) Ethernet/WiFi ATM/Fiber Optics CS 414 - Spring 2010

  5. TCP- Transmission Control Protocol - Features • Serial communication path between processes exchanging a full-duplex stream of bytes • Sequential delivery (no reordering required) • Reliable delivery • Achieved through retransmission via timeouts and positive acknowledgement on receipt of information • Flow and congestion control is based on window technique CS 414 - Spring 2009

  6. TCP Header CS 414 - Spring 2009

  7. Flow and Congestion Control in TCP • Slow-start algorithm – basic flow and congestion control in TCP • The algorithm requires sender to keep congestion window which is the estimate of how much traffic the network can actually take (in-network traffic) • Congestion window is managed using two-part algorithm: • Sender sends exponentially until TCP segment gets lost • Sender sends exponentially up to half the previous window, then window grows linearly CS 414 - Spring 2009

  8. Techniques for Going Faster • TCP predictions (1987) that TCP/IP cannot go faster than 10 Mbps • Van Jacobson investigated making TCP faster • Techniques: • Memory management – reduce copying • Interrupt handling – clocked interrupts CS 414 - Spring 2009

  9. Techniques for Going Faster • Better lookup techniques • TCP must lookup connection block for each segment received • IP must find a route to be able send IP packet • Use caches of frequently used information • Maximize hit rate, minimize search and maintenance • Most effective – small caches • Packets travel in packet rates • CACHE OF 20 ROUTES SHOWED HIT RATE OF 90% CS 414 - Spring 2009

  10. Techniques for Going Faster • Lookup algorithm • Hashing using open chaining – head of each hashed link list keeps a cache of the last accessed control block • Prediction • TCP behavior is highly predictable and one can take advantage by optimizing the frequent path through TCP code at sender/receiver • Header prediction CS 414 - Spring 2009

  11. Sequence Numbers • High delay-bandwidth product has implication on TCP window size and sequence space; • Delay-bandwidth product means how many bytes (represented via packets) are currently in-flight (i.e., inside the network) • Example: • If EED is 1 second and network bandwidth (inside network) is 10 Mbps, then delay-bandwidth product is equal to 10 Mbits (1second * 10 Mbps) and this means that one can have 10 Mbits worth of data inside the network before seeing it at the receiver • TCP window size is 64 KB – we need possibility to negotiate the window size CS 414 - Spring 2009

  12. Sequence Numbers • Sequencing uses wrap-around counters to put in sequence numbers • Sequence number space is too small • Examples: • In case of 10 Mbps, the IP packet lifetime was designed with 120 seconds and sequence space of 32 bits – takes about 1700 seconds to send 231 bytes • In case of 1 Gbps, it takes 17 seconds to send 231 bytes CS 414 - Spring 2009

  13. Layer 3 Internet Services • Internet Protocol (IP) – IP Version 4 • Provides unreliable deliver of datagrams in a point-to-point fashion • Runs on top of any Layer 2 technologies • Supports • IP address of 32 bits • Different types of services (TOS) • Precedence relation • Services such as minimization of delay, maximization of throughput • Multicast • Internet Group Management Protocol for managing groups CS 414 - Spring 2009

  14. New Internet Protocol - IPng • Next Generation IP – IP Version 6 • Supports new features • New addressing and routing • IP Address 128 bits • Large hierarchical addresses, multicast addresses • More options of flow control and security • Real-time flows • End-to-end security • Provider selection • Host mobility • Auto-configuration/auto-reconfiguration • Traffic Classes CS 414 - Spring 2009

  15. IP Packet Headers Version Header Length TOS Total length identification Flag Fragment offset Time to Live (TTL) Protocol Header Checksum IPv4 32-bit Source IP Address 32 bit Destination IP Address Version Traffic Class Flow Label Payload Length Next Header Hop limit IPv6 128-bit Source IP Address 128-bit Destination IP Address CS 414 - Spring 2009

  16. QoS in Layer 3 - Internet Integrated Services • To provide network QoS in the Internet, IETF reacted by • Creating Working Group (IntServ) • Deploying Internet Integrated Services • Development of Control (Establishment) Protocol to reserve resources per flow • Resource Reservation Protocol (RSVP) • Development of QoS-aware network services within IP • Guaranteed class-of-service • Deterministic QoS guarantees • Controlled-load class-of-service • Statistical QoS guarantees CS 414 - Spring 2009

  17. Integrated Services (IntServ) Architecture Reservation Protocol (RSVP) End-system Router Control Plane Policy control Policy control RSVP daemon RSVP daemon Appl. Routing. Admission control Admission control Packet scheduler Packet classification Packet scheduler Error Handling Data Plane CS 414 - Spring 2009

  18. Conclusion Improvements of existing transport protocols such as TCP are happening to support multimedia real-time traffic Improvements of existing IP protocols such as IP are happening to support multimedia real-time traffic CS 414 - Spring 2010

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