Internet protocols for multimedia
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Internet Protocols for Multimedia. DS VT-00 Jerry Eriksson. Multimedia Networking. Animation, voice and video - not only text distance learning, distributed simulation, distribute work groups Multimedia networks may replace telephone, television, etc

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Internet protocols for multimedia

Internet Protocols for Multimedia

DS VT-00 Jerry Eriksson


Multimedia networking

Multimedia Networking

  • Animation, voice and video - not only text

  • distance learning, distributed simulation, distribute work groups

  • Multimedia networks may replace telephone, television, etc

  • Challenges - Build hardware and software infrastructure and applications to support multimedia


Outline

Real-time challenges

Real-time protocols

RTP, RTCP, RTSP

QoS

Definitions

Goals

Traffic management architectures

IntServ, Diffserv, RSVP

VoIP

H.323, SIP

Outline


Real time challenges

Real-time Challenges

  • High bandwidth

  • Audio and video must be played back at the rate they were sampled (voice may be even more difficult)

  • Multimedia data streams are bursty


Internet

Internet

  • Primary reason: Platform for most networking activities

  • Integrated data and multimedia service over a single network (investments)

  • Not suitable for real-time traffic

    • Offers only best-effort quality


Problems to solve

Provide enough bandwidth

Provide multicast to reduce traffic

Provide protocols that handle that that care of timing issues

Delay, Jitter

QoS- guarantee quality

Reserve resource on the internet

Transport protocols

Presentation of the multimedia data (WAP, Voice)

Charging and policing mechaninsm

Problems to solve


Qos definitions

QoS Definitions

  • Qos is a set of technologies that enables network administrators to manage the effects of congestion on application traffic by using network resources optimally

  • or, allocate different resourses for different data flows


Qos classes

QoS classes

  • Best-effort - No gurantees at all

  • Soft QoS - differentiated guarantess

  • Hard QoS - full guarantees


Rtp real time transport protocols

RTP- Real-time transport protocols

  • Ip-based protocol providing

    • time-reconstruction

    • loss detection

    • security

    • content identification

  • Designed primarily for multicast of real-time data (also unicast, simplex, duplex)


Rtp development

RTP - development

  • December 1992, Henning Schulzrinne, GMD Berlin, published RPT version 1

  • Proposed (version 2) as standard November,1995

  • Netscape and Microsoft uses RTP


How does rtp works

How does RTP works

  • Timestamping - most important information for real-time applications.

    • The sender timestamp according to the instant the first octet in the packet was sampled.

    • The receiver uses timestamp to reconstruct the original timing

    • Also used for synchronize different streams; audio an video in MPEG. ( Application level responsible for the actual synchronization)


How does rtp work

How does RTP work

  • Payload type identifier

    • specifies the payload format as well as encoding/compression schemes

    • The application then knows how to interpret the payload

  • Source identification

    • Audio conference


Where is rpt reside

Where is RPT reside

  • RPT is typically run on top of UDP

    • Uses UDP’s multiplexing and checksum functions

  • RPT is usually implemented within the application (Lost packets and congestion control have to be implemented in the application level


Rtcp real time control protocol

RTCP - Real Time Control Protocol

  • Designed to work together with RTP

  • In an RTP session the participants periodically send RTCP packet to give feedback on the quailty of the data.

  • Comparable to flow and congestion control of other transport protocols.

  • RTP produces sender and receivers reports; statistics and packet counts


Rtct packet types

RTCT packet types

  • Recevier reports: feedback of data delivery

    • Packet lost, jitter, timestamps

  • Sender report:

    • Intermedia synchronization, number of bytes sent, packet counters

  • SDES, BYE, APP


Rtcp provides the following services

RTCP provides the following services

  • QoS monitoring and congestion control

    • Primary function: QoS feedback to the application

    • The sender can adjust its transmission

    • The receiver can determine if the congestion is local, regional, or global

    • Network managers can evaluate the network performance for multicast distribution


Rtcp provides the following services cont

RTCP provides the following services (Cont)

  • Source identification

  • inter-media synchronization

  • control information scaling

    • Limit control traffic (most 5 % of the overall session traffic)


Rtp rtcp features

Provides

end-to-end real-time data delivery (functionality and control mechanisms)

timestamps sequences numbering (up to the application to use it)

Uses UDP

Provides not

timely delivery (needs lower layer reservations)

any form of reliability or flow/congestion control (RTCP)

Not complete - new payload format

RTP/RTCP features


What is streaming

What is Streaming?

  • Streaming breaks data into packets; real-time data through the transmission, decompressing just like a water stream.

    • A client can play the first packet, decompress the second, while receiving the third.

    • The user can start enjoying the multimedia without waiting to the end of the transmission


Rtsp real time streaming protocol

RTSP - real time streaming protocol

  • Client-server multimedia presentation protocol to enable controlled delivery

    • provides ”vcr”-style remote control functionality of streamings over IP.

    • RTSP is an application-level protocol designed to work with RTP (and RSVP) to provide a complete streaming service over internet

    • It provides means for choosing channels (UDP etc) and delivery mechanisms (RTP)

  • Developed by RealNetworks, netscape, and columbia university (still an internet draft)


Rtsp operations and methods

RTSP operations and methods

  • RTSP establish and controls streams

  • A media server provides playback or recording services

  • A client requests continues media data from the media server

  • RTSP is the network is the ”network remote control” between the server and the client


Rtsp provides

RTSP provides

  • Retrieval of media from media server

  • Invitation of a media server to a conference

  • Adding media to an existing presentation

  • Similar services on streamed audio and video, just as HTTP does for text and graphics


Http rtsp differences

HTTP/RTSP differences

  • HTTP stateless protocol; an RTSP server has to maintain ”session states”

  • HTTP is asymmetric; in RTSP both client and server can issue requests

  • It uses URL, like HTTP


Resources reservation and prioriations

Resources reservation and prioriations

  • Any QoS better than best-effort.

    • Routing delays and congestion losses

  • Real-time traffic


Now ip qos networking integrated services

Now IP QoS Networking -Integrated services

  • Defined by an IETF working group to be a key-stone

  • IS was developed to optimize network and resource utilization which require QoS.

  • Divided traffic between into different QoS classes.

  • An internet router must be able to provide an appriopriate QoS for each flow. (according to a service model)


Router function traffic control

Router function: Traffic control

  • Packet scheduler manages forwarding of different packet streams.

    • Service class, queue management, algorithms

    • Police and shape traffic

    • must be implemented at the point where the packets are queued.


Router function traffic control1

Router function: Traffic control

  • Packet classifier indentifies packets of an IP flow in hosts and routers that will receive a certian level of service.

    • Each packet is mapped by the classifier into a specific class. (same class, same treatment)

    • The choice of class is based upon the source and destination, and port number in packet header


Admission control

Admission control

  • Decision algorithms that a router uses to determine if there are routing resources to accept the requested QoS for a flow

    • If the flow is accepted; the packet classifier and packet scheduler reservs the requested Qos for this flow.

  • Checks user authentification

  • Will play an important role for charging


Intserv cont

IntServ (cont)

  • Communicates with RSVP to create and maintain flow-specific states in the endpoint hosts and in routers along the path of a flow

  • RSVP/Intserv are complementary

  • Not suitable for high volume traffic (speech)


Differentiated services

Differentiated services

  • IETF working group (draft, no RFC)

  • Simplify scheduling and classification using the priority bits in the IP header.

  • Packet flow must be marked according to SLA; Servive Level Agreements at the edge of the network

  • The ISP must assures that a user gets his requsted QoS.

  • Improves scalability greatly.


Mechanisms needed

Mechanisms needed

  • Setting bits in DS at the network edges and administrative boundaries

  • Using those bits to determine how packets are treated by routers inside the network

  • DS architecture is currently asymmetric;

    • on-going research for symmetric architecture


Diffserv architecture

Diffserv architecture

  • Static and long-term

    • Not need to set up QoS reservation for specific data packets

    • DS routing example (it is not that easy)

  • Handle aggregate traffic (not per-conversation)

    • require significantly less sates and processing power than per-conversation.


Rsvp reservation protocol

RSVP - reservation protocol

  • Internet control protocol - not routing protocol

  • Runs on top of IP and UDP

  • Key concepts: flows and reservations

  • Applies for a specific flow of data packets on a specific path. Each flow has a flow descritpor.

  • Both unicast and multicast.

  • Doesn’t understand the content of the flow descriptor


Rsvp reservation protocol1

RSVP - reservation protocol

  • Simplex protocol; reservation is done in one direction;

  • Receiver-initiated. The sender sends QoS wanted to the receiver which sends an RSVP message back to the sender.

  • The sender does not need to know the capabilities along the path or at the receiver


Rsvp reservation protocol2

RSVP - reservation protocol

  • The RVSP daemon

    • checks admission and policy control. If either fails the RSVP returns error

    • sets parameters in the packet classifier and packet scheduler

    • communicates with the routing process to determine path


Reservation messages path and resv

Reservation messages PATH and RESV;

  • PATH messages are periodically from the sender to the receiver and contains a flow spec

    • data format, source address, source port

    • traffic characteristics

  • RECV is generated by the receiver and contains flow spec and filter spec

    • follows the exact reverse path setting up reservations for one or or more senders at each node


Intserv drawbacks

Intserv drawbacks

  • Only implemented for UNIX platforms

  • Must be implemented on each node from ’end’-end’ - not scalable

  • No secure policy mechanisms

  • Protecting multimedia - most traffic still are non-multimedia

  • Close to death, September 1997


Rsvp renaissance today

RSVP renaissance today

  • Availability of RSVP signaling on a large number of hosts (Windows 2000)

  • Use Diffserv as well.

  • Availability of policy components and products from many vendors.

  • Recent work on RSVP signalling handle non-multimedia much better


Top down provisioning

Top-down provisioning

  • Low overhead and aggregate traffic handling. Bilateral agreements

  • Difficulty learning the classification criteria that should be configured to specify specific traffic

  • Cannot offer high-quality guarantees required for multimedia applications, unless the network is overdimensioned

  • Top-down provisioning to coordinate traffic handling along a specific path


Youram bernet

Youram Bernet

The combination of RSVP signaling

with aggregate traffic handling mechanisms

is able to address the deficiencies of the

exclusively top-down provisioned approach

without incurring the scalability problems

of classical RSVP/intserv usage


Enhancing efficiency within diffserv network

Enhancing efficiency within diffserv Network

  • Diffserv provider may dedicate resources support SLA

  • Statistical multiplexing

  • Dynamic signalling at certain key points;

    • dynamic admission control


Yoram bernet

Yoram Bernet

When managing a network to offer QoS,

the manager is faced with certain trade-offs.

A given network and its QoS mechanisms can

offer a certain quality of guarantees at a certain

level of efficiency.


Quality efficiency

Quality/efficiency

  • Trade-off; An on-going debate

    • Over-provision the network;Efficiency decreases

    • Lower the resourses;Decrease QoS.

  • It is impossible to aviod the overhead of more sophisticated QoS mechanisms unless on is willing to compromise in the trade-off just mentioned


Yoram bernet qos expert microsoft

Yoram Bernet, QoS expert Microsoft

Despite the astounding rate at which netork

capacity is increasing, we find ourselves

contending with congested networks today and

can expect ot do be doing so for the

foreseeable future


Why ip telephony voip

Why IP telephony (VoIP)

  • Regarded far too unreliable for mass market, but now reliability and quality have quickly improved

  • Advantages: Cheaper

    • No inter-connect charges; 6-8 kb/s (packet) vs 64kb/s

    • Regulation costs

  • New value-added features; conferencing

  • Single network


Internet telephony standards

Internet telephony standards

  • Still immature; latency major issue

  • ITU-T: H.323 (set of protocols)

  • SIP used to initate a session between users. Simple, cheap. Limited, but popular


H 323 standard architectures

H.323 Standard architectures

  • Protocol stack (fig. 9-4)

    • Audio, video over RTP/RTCP/UDP

    • Data over TCP

    • System Control over TCP


H 323 architecture

H.323 Architecture

  • Components

    • Gateway

    • Gatekeeper

    • MCU

  • Interwork with SS7


Signalling within h 323

Signalling within H.323

  • H.323 uses a logicla channel on the LAN

  • RAS (Registration, admission and status)

    • Gatekeeper Discovery

    • Endpoint registration

    • Call management

    • Admission procedures

    • and several more


Voipow over wireless wcdma

VoIPoW (over wireless (wcdma))

  • Rather important reserach in Ericsson

  • Challenge cube


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