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Page 1: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

CMSC691C Multimedia Networking

A Course OverviewPadma Mundur

CSEE, UMBC

[email protected]

Page 2: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

List of Topics

Multimedia Networking: Source Representations, Networks, and Applications

Multimedia Compression Fundamentals & Coding Standards

Scalable Video Coding for Heterogeneous Networks Fundamentals of IP Routing IETF QoS Efforts Existing Solutions for Scalable Multimedia QoS

Page 3: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

The Telephone (Voice) Network• Circuit switched network:

– Analog (since1890): manually switching– Digital: voice bit stream (64 Kbps)– Better channel utilization by time-division multiplexing:– Reservation fixed for the whole transmission

A

B

C

Page 4: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

The Internet (Data) Network• Packet-switched network:

– packets share resources (buffers, links)– reservation not fixed, but on-demand– multiple links (connectivity, reliability)– buffers (store, process, forward)– control information in packets (s,d,seq#)

Page 5: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Internet Users Growth

Source: www.isc.org

1B mobile users by 2005 and 1B Internet users by 200590% of all new mobile phones will have internet access by 2003 (Morgan Stanley Dean Witter, May 2000)

Page 6: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Multimedia over IP Networks

Music Streaming

Information SearchMovies

StreamingFinance,

Brokerage

Digital Photos

Internet

E-mail

Video ClipAttachment

VideoConference

VoIP

Wireless Wireless BrowsingBrowsing

Page 7: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Multimedia Networking Applications

• Media Broadcast: simultaneous pushing of content to multiple recipients– Network IP Multicast – Multicast enabled routers and

switches

• Hosted Streaming: content users initiate requests and content networks/providers push content through network

• Interactive Conferencing: no centralized source of contents

Page 8: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Internet

content provider

clients

Multimedia Broadcast over IP

IP (internet protocol) makes it

possible to link all (global) nodes together independent of applications and terminal devices

Page 9: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Hosted Multimedia Streaming

MediaEncoding

AudioVideoAnimation

Clients

Send RequestTo ServersWeb

Server

Send Request to Media Server

MediaServer

ProprietaryFormat

•Multicast capable•More Robust•Access to Storage•Relieves Web Server

Send StreamTo Clients

•Standalone player•Java based player•Browser plug-in player•Appliance

•Decode•Buffer•Sync.

To hear or view a media file without downloading it

Page 10: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Bandwidth concern for multipoint interaction

Internet

Interactive Conferencing and Meeting Server

Page 11: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Meeting Client

Token

Meeting Token Holder

How A Server Distributes the Data

Page 12: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Meeting Client

Token

Old Token Holder New Token Holder

Dynamic Token Passing

Page 13: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Multimedia Signals and Bitrates

96 Kbps

224 Kbps

1.412 Mbps

(2 channels)

90 Kb/inch2

6.3 Mb/image

248.8 Mbps

248.8 Mbps

31 Mbps

37 Mbps

2.3 Mbps

12

14

16/channel

1

24

24

24

12

12

12

8000 samples/sec

16,000

44.1 Ks/sec

300 dpi (dots/inch)

512x512

720x480x30

720x576x25

360x240x30

352x288x30

176x144x7.5

200—3400

50—7000

20—20,000

Telephone Voice

Wideband speech

Wideband audio

(2 channels)

B/W documents

Color Image

CCIR-601 (NTSC)

CCIR-601 (PAL)

SIF (standard)

CIF (common)

QCIF (quarter)

Bit RateBits per

Sample

Sampling

Rate

Bandwidth

(Hz)

Source

Page 14: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Audio & Video Quality Requirements

Page 15: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IP Networks• IP uses packet switching

– Suitable for unexpected burst of data without establishing an explicit connection.

– Bandwidth is shared statistically so data can be sent at any time.

• IP is not reliable nor delay-bounded.– Best effort– Queuing delay, especially when congested.– Network failures can cause temporary packet loss. Time critical applications cannot operate well due to large e-mail

attachments and Web surfing Delay and jitter degrade voice and video performance

Page 16: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Multimedia Signals

• Text• Speech • Audio• Image (B/W and color)• Video• Graphics & Animation• Documents (various formats)

Page 17: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Image & Video Coding Standards• Combination of lossy (transform coding) and lossless (run-

length, Huffman, Arithmetic coding, LZW, etc) coding techniques along space and time.

• JPEG - Joint Photographic Experts Group•Still image compression, intraframe picture technology

•Motion JPEG (MJPEG) is sequence of images coded with JPEG

• MPEG - Moving Picture Experts Group•Defined by ISO/IEC, several standards MPEG1, MPEG2, and now MPEG4

• H.263/H.263+/H.26L - Videophone/Conferencing•Low to medium bit rate, quality, and computational cost defined by ITU

•Used in H.320 and H.323 video conferencing standards

Page 18: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

A Complete JPEG Encoding DCT

Zig-zag Quantize

Run-length Code

Huffman Code

011010001011101...

Page 19: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

From Image to Video Coding• Intra-frame compression (similar to JPEG)

•Remove redundancy within frame (spatial)

• Inter-frame compression (motion compensation)•Remove redundancy between frames (temporal)

• Rate Control (constant bit-rate or constant SNR)

Page 20: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Video Coding Standards MPEG1 – VHS quality, VCD (1992)

•CIF images, 4:2:0 sampling, 1.5 Mbs, Frame encoding MPEG2 - broadcast quality, HDTV and DVD (1994)

•CCIR 601 images, 4:2:2 sampling, 4-15 Mbs•Interlaced and progressive scanning, Frame and field

H.261 for videotelephony (p=1,2) & videoconferencing (p>= 6) (1992)•Improve JPEG through temporal redundancy

H.263 – low bitrate video coding (1995)•Half pixel motion compensation, 4 (optional) modes•Optimized VLC tables & better motion vector prediction

H.26L(H.264) – flexible, high quality video applications (2002)•1/4 pixel accuracy for MC, 7 different block sizes for ME/MC•Residual coding uses 4x4 blocks & an integer transform

Page 21: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

MPEG-4: An Emerging Standard

• For multimedia applications – Interactive natural & synthetic contents– Various access conditions: low bit-rate, error prone, heterogeneous

(scalable)– Management and protection of media contents

• Standard– 1st generation (1998-2000): 1st+2nd versions, frame based content

creation & communication, 64-384 Kbps, mobile videophone (3G and IP) and digital camcorder

– next generation (2001-): upto 2Mbps, frame/object based, scalable streaming, interactive set-top box

Page 22: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Heterogeneous IP Networks Adaptive Rate Control Scalable Coding

Real-time bandwidth estimation Receiver feedback Adaptive Multicast control

Page 23: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Video Scalable Coding• Why a scalable video codec?

– Compression efficiency– Robustness with respect to packet loss– Adaptation to the changing bandwidth

• Techniques of scalable video coding– Temporal– Spatial– Signal-to-Noise Ratio (SNR)– Data Partition– Wavelet– Fine Granularity Scalability (FGS)

Page 24: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IP Stack: A Layered Architecture

Application

Transport

Network

Physical

usersnetwork

Web (HTTP), E-mail (SMTP),File transfer (FTP), Name resolution (DNS), Remote terminal (TELNET), …

Reliable multi-connection bit-stream (TCP),unreliable multi-connection (UDP).

Unreliable end-to-end delivery ofpackets up to 64 KB.

Point-to-point links (PPP, SONET, …),LANs (Ethernet, FDDI, wireless, …)

Page 25: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IP Packet Routing: Delay and Loss

A

B

propagation

transmission

nodalprocessing queue management

A

B

propagation

transmission

nodalprocessing queue management

Hello

Hello

IPNetwork

Router

Router

Router

Router

Router

Router Router

Router

Router

Page 26: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Queuing and Scheduling (1) FIFO - First In First Out queuing, definitely not

compatible with QoS since high priority packets can get stuck behind low priority packets

Page 27: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Queuing and Scheduling (2) Priority Scheduling - services higher priority queue

whenever there are packets present, can lead to starvation of lower priority queues

Page 28: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Queuing and Scheduling (3) Custom Queuing (or Weighted Round Robin Scheduling) - services all

queues (with different service time) within a traffic class, round robin assuring that all queues get appropriate treatment

Page 29: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Queuing and Scheduling (4) Weighted Fair Queuing (WFQ) - queue is serviced based on a weight

proportional to the bandwidth dynamically allocated to it

Page 30: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Congestion Control & Queue Discard

Tail Drop– Drops arriving packets when buffers in queue are full, can

lead to network meltdown due to TCP global synchronization

RED = Random Early Detection– Queuing algorithm for congestion avoidance that randomly

discards packets from queues in an attempt to prevent TCP retransmits simultaneously on all flows

Page 31: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Congestion Control & Queue Discard

WRED = Weighted Random Early Discard– A variant of RED that attempts to weight queues for random

early discard

Tri-Color Marking (deterministic)

RedDrop

Threshold

YellowDrop

Threshold

QueueLimit

Page 32: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IP QoS and Multimedia

• Quality of Service (QoS) methods aim at trading quality vs. resources to meet the constraints dictated by the user, the functionality and the platform.

• QoS originally developed in network communication, and recently extended to the domain of multimedia communication.

• QoS relevant in multimedia scalable systems, where the resources and the functionality can be controlled by a set of parameters.

Page 33: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IP Quality of Service (QoS) Techniques to intelligently match the performance needs of applications to available network resources

QoS Metrics•availability

•delay (latency)

•delay variation (jitter)

•throughput (average and peak rates)

•packet loss

Page 34: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IETF IP QoS Efforts

• Policy based IP QoS Solutions– Integrated Services (RSVP protocol): flow based– Differentiated Services (DiffServ byte settings): packet based– Multi-Protocol Label Switching (MPLS): flow+packet based

• IP Multicast and Anycast• IPv6 QoS Support

Page 35: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Connection Oriented QoS Int-Serv (Integrated Services): IETF RFC 1633

Defined by RSVP requires resource reservation at each hop end-to-end for each IP packet flow, and end-to-end signaling along nodes in the path

Reserve resources at the routers so as to provide QoS for specific user packet stream

This architecture does not scale well (large amount of states) Many Internet flows are short lived, not worth setting up VC

Page 36: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Integrated Services / RSVP Sender sends a “PATH” message to the receiver specifying characteristics of traffic

• every intermediate router along the path forwards the “PATH” message to the next hop determined by the routing protocol

Receiver responds with “RESV” message after receiving “PATH”. “RESV” requests resources for flow

Page 37: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Connectionless QoS: IP Diff Serv Mark IP packet to specify treatment: IETF RFC 2474, e.g., first

class, business class, coach, standby Per Hop Behaviors (PHBs) based on network-wide traffic classes Flows are classified at the edge router based on rules, and are

aggregated into traffic classes, allowing scalability Diff Serv uses the IP header TOS byte (first 6 bits), which is

renamed the DS field Diff Serv defines code points (DSCP) for the DS field, DE (default)

= 000000 = best effort, and EF (Expedited Forwarding) = 101110 = low latency, etc.

Page 38: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

DiffServ Operation Each ISP configures its own routers to match the service that it offers, and each ISP has its own DiffServ Domain.

DS DomainDS DomainDS DomainDS Domain

VoiceVoice

ASPASPVideoVideo emailemail

Customer SiteCustomer Site

SLA(service level agreement) SLA

SLA

PHB PHBPHB

Edge RouterInterior Nodes

Page 39: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

MPLS Fundamentals MPLS is a forwarding scheme that tags packets with labels

(independent of layers 2,3) that specify routing and priority (IETF RFC 3031)

Enables scalability by alleviating IP over ATM problems• Defines a homogeneous network based upon label-switching• Requires all devices (i.e., ATM switches) to be capable of routing

Enables differentiated services via QoS-aware label switched paths (LSPs)

Designed to run over a wide range of media• ATM, frame relay, and Ethernet

Page 40: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Unicast/Multicast

Host

Router

Unicast

Host

Router

Multicast

Page 41: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Why multicast?• When sending same data to multiple receivers• Better bandwidth utilization • Lesser host/router processing• Receivers’ addresses unknown

Applications• Video/audio conferencing• Resource discovery/service advertisement• Media streaming and distribution

Multimedia IP Multicast

Page 42: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IETF RFC 1112, each multicast group is identified by a class D IP address

•Range from 224.0.0.0 through 239.255.255.255

Well known addresses designated by Internet Assigned Number Authority (IANA)

•Reserved use: 224.0.0.0 through 224.0.0.255

Members join and leave the group and indicate this to the routers

Multicast routers listen to all multicast addresses and use multicast routing protocols to manage groups

IP Multicast Service Model

Page 43: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

What IPv6 can Offer?

• Global Addressing (128 bits): – 1 million networks per human– 20 hosts per m2 of Earth

• Plug and play: • Efficient mobility (instant-on ad-hoc networking)

128-n bitsn bits

who you are where you are connected to

Page 44: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IPv6: Key Features and Advantages• Increased Address Space (128 bits)• Efficient and extensible IP datagram• Improved host and router discovery• Plug and Play• Enhancements for Quality of Service (QoS) • Improved Mobile IP support• Coexistence with IPv4• Built in security (authentication and encryption) in IP layer

Page 45: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

IPv6 Support of QoS• IPv6 Flow Labels provide support for Data Flows

– Packet Prioritizing-- sure that high priority traffic is not interrupted by less critical data

• IPv6 supports Multicast & Anycast– Multicast delivers data simultaneously to all hosts that

sign up to receive it

– Anycast allows one host initiate the efficient updating of routing tables for a group of hosts.

Page 46: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Existing Scalable Multicast Solutions

• Content Distribution Networks• Receiver-Driven Layer Multicast (RDLM)• Source Adaptive Multi-Layer Multicast (SAMM)• Filtering Method• Destination Set Grouping (DSG)• Multiple Description Coding (MDS) of Multimedia

Page 47: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Distributing Content to the Edges

Adding backbone bandwidth is not the best solution, the last mile (edge) connection is even more critical.

How to direct traffic to the site (routing) and resolve the appropriate server (load balancing) that will perform best for a particular query (front-end content delivery).

How to keep content updated efficiently (back-end content delivery)

Page 48: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Getting Contents to the Edge Caching (on-demand “pull”)

– Contents may be “pulled” from another proxy cache in the hierarchy or the origin of the contents.

– Problems: stale content delivery, hit statistics loss, dynamic contents Replication (changes made on the origin server)

– Updates are “pushed” to replica using a “back-end” content delivery system.

– The origin server is in total control (database keep track of content changes), with scalable architecture (multicast or packet-relay).

Page 49: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Getting Contents to the Edge Resolution Problem

– The best site: geographic vs. network proximity (quickest service)

– Domain Name Service (DNS) criteria: # of authoritative servers (domain) hops, # of router hops, health/load of site, round trip latency, packet loss rate, etc.

Hybrids of Caching/Replication Reverse Proxy Cache: all queries directed to proxy caches by

load balancer for front-end delivery. Pre-Filling of Proxy Caches: parts of the Web site are pre-filled

to the cache – i.e., replica in proxy cache form

Page 50: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Content Distribution Network (CDN) Service providers using proprietary caching/replication

technologies to build overlay networks (internet or satellite) to deliver contents – application level multicast

Page 51: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Receiver-driven Layer Multicast (RLM)

• RLM Protocol Concepts (McCanne 1996): Source: No active role in the protocol. Receivers: On congestion, drop a layer.

On spare capacity, add a layer. When to drop a layer:

Whenever congestion happens. Congestion is expressed explicitly in the data stream through lost packets.

• When to add a layer:Join-experiment: To carry out active experiments by spontaneously adding layers at “well chosen” time.

Page 52: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

RLM Characteristics

A fixed number of multicast groups. Lack of granularity adaptation Severe quality degradation when pack loss

on base layer. Slow adaptation to changes of varying

network bandwidth (Liu, Hwang 2002) Synchronization is crucial Well-developed protocol is crucial

Page 53: CMSC691C Multimedia Networking A Course Overview Padma Mundur CSEE, UMBC pmundur@csee.umbc.edu.

Source Adaptive Multi-layer Multicast SAMM Protocol Concepts (Suda

1998):

Video is encoded into several layers and each layer has an unique discarding priority.

When a network link experiences congestion, packets from the lowest priority layer are discarded.

The video source obtains backward feedbacks from receivers to adjust the number of video layers and also the encoding rate for each layer.