cs 414 - spring 2011 cs 414 – multimedia systems design lecture 22 – multimedia extensions to...

CS 414 - Spring 2011

CS 414 – Multimedia Systems Design

Lecture 22 – Multimedia Extensions to Existing IP Protocols

Klara Nahrstedt

Spring 2011

Outline

Multimedia IP Extensions (Layer 3)


Internet Multimedia Protocol Stack


AAL3/4

IP Version 4, IP Version 6

UDP

Media encaps(H.264, MPEG-4)

RTP

ATM/Fiber Optics Ethernet/WiFi

TCP

SIP RTSP RSVP RTCP

AAL5

KE

RN

EL

AP

PLIC

AT

ION

Layer 4(Transport)

Layer 3(Network)

Layer 2(Link/MAC)

Layer 5(Session)

MPLS

DCCP

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


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


IP Packet Headers


Version Header Length TOS Total length

identification Flag Fragment offset

Time to Live (TTL) Protocol Header Checksum

32 bit Destination IP Address

32-bit Source IP Address

Version Traffic Class Flow Label

Payload Length Next Header Hop limit

128-bit Source IP Address

128-bit Destination IP Address

IPv4

IPv6

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


Integrated Services (IntServ) Architecture


Appl.RSVPdaemon

Policycontrol

Admissioncontrol

Packetscheduler

Packetclassification

Routing.RSVPdaemon

Policycontrol

Admissioncontrol

Packetscheduler

Error Handling

Reservation Protocol (RSVP)End-system Router

Control Plane

Data Plane

RSVP Provides reservation for data flows

Flow specification is represented via

Traffic specification, TSpec Characteristics of the data flow

Request specification, Rspec Description of required QoS (desired flow behavior)

Is receiver-oriented and unidirectional Uses two types of messages:

PATH messages and RSVP messages

Protocol 1. Send PATH message with TSpec from Sender to Receiver(s)

2. Send RESV message with Rspec from Receiver(s) to Sender

3. Send DATA with resulting reserved QoS


Flow Specification (1)(Traffic Shape General Parameters)

Peak rate – highest rate at which a source can generate traffic

Average rate – average transmission rate over a time interval

Burst size – max amount of data that can be injected into network at peak rate


Flow Specification (2)(in IntServ)

Traffic described in terms of token bucket parametersToken arrival rate ‘r’Bucket depth ‘b’

Amount of bits transmitted during any interval of length t: A(t) ≤ r * t + b


Service Requirements (Application-specific)

Minimum Bandwidth - min. amount of BW required by application

Delay – can be specified as average delay or worst case delay Propagation delay + Transmission delay + Queuing

delay Delay Jitter – specifies max. difference between the

largest and smallest delays that packets experience Loss Rate – ratio of lost packets and total packets

transmitted


RSVP Control and Data Flow


RESV messages

PATH messagesDATA

S1

D3

D1

D2

R1 R2

R3 R4

(1) TSpec

(2) TSpec,RSpec

(1) TSpec

(1) TSpec

(2) Tspec,RSpec

(2) Tspec,RSpec

(1)

(1) (2)(2)

(3)

(3)(3)

(3)

(3)

Mixing Reservations


RESV messages

PATH messagesDATA

S1

D3

D1

D2

R1 R2

R3 R4

15MB

10MB

15MB

15MB

3MB

12MB

Mixing

3MB10MB

15MB

12MB

Mixing

12MB

Reservation Structures

Resource Reservation TableStores admitted/reserved resources

RSVP Messages


Version Flags

Send TTL

Message Type

Reserved

RSVP Checksum

RSVP Length

RSVP Features Simplex Reservation

Reservation only in one direction (simplex flow) Receiver Oriented

Supports multicast communication Routing Independent Policy Independent Soft State

Reservation state has timer associated with the state When timer expires, state is automatically deleted RSVP periodically refreshes reservation state to maintain state along the

path


Service Models

Describe interface between network and its users in resource allocation architecture

Describe what services users can ask from network and what kind of resource commitments the network can offer

IntServ standardGuaranteed ServiceControlled-load Service


Guaranteed Service(in IntServ) Provides guaranteed BW and strict bounds on end-to-

end queuing delay for conforming flows Controls max. queuing delay TSpec – describes traffic sources

Bucket rate (‘r’) (bytes/second) Peak rate (p) (bytes/second) Bucket depth (b) (bytes) Minimum policed unit (m) (bytes) – any packet with size smaller

than m will be counted as m bytes Maximum packet size (M) (bytes) – max, packet size that can be

accepted


Guaranteed Service (2) Rspec

Service rate (R) (bytes/second) – service rate or BW requirement

Slack term (S) (µsec) – extra amount of delay that a node may add that still meets the EED (end-to-end delay) requirement.

This service does policing and shaping Resources are reserved at worst case For bursty traffic sources – low network utilization


Controlled Load Service(in IntServ) No quantitative guarantees on delay bound or BW This service model allows statistical multiplexing –

statistical guarantees Very high % of transmitted packets will be successfully delivered Transit queuing delay experienced by a very high % of delivered

packets will not greatly exceed min. delay

Invocation and Policing Specify TSpec (average values) and do admission, reservation,

policing based on average TSpec


IntServ (Error Handling - Early Congestion Avoidance)


Packet Scheduler

Input Queue

IP packet

IP packet

IP packet

IP packet

IP packet

IP packet

MinThres – Min. Queue Length Threshold

MaxThres – Max QueueLength Threshold

Avr – Average Queue Length

IntServ (Error Handling) Discard Algorithms RED: Random Early Detection

single FIFO queue is maintained for all packets and packets are dropped randomly with a given probability when the average queue length exceeds minimum threshold (MinThresh).If max. threshold (MaxThres) is exceeded, all packets are dropped

WRED – Weighted RED Drops packets selectively based on IP precedence



Incoming IP packet

Compute Avr

Calculate Packet drop probability

Drop packetEnqueue packet

Avr < MinThres Min < Avr < Max Avr > MaxThres

Low probability High

RED

Packet Scheduling (in IntServ)

Isolation versus Sharing Circuit-switched network (e.g., telephone network) – all

flows are isolated, i.e., each connection has dedicated resource

Datagram-based Internet – all resources are shared on per-packet basis without any form of isolation and protection

IntServ requires scheduling algorithms to support delay bounds Deterministic or statistical delay bounds Deterministic and statistical bounds reflect trade-offs between

isolation and sharingCS 414 - Spring 2010

Packet Scheduling(in IntServ) Simple Priority

Be careful – a large volume of higher-priority packets can easily starve lower-priority packets

Fair queuing approach Allocate BW proportional to active flows based on their weights

Deadline-based schemes Use EDF on packets

Rate-based scheduling framework Has two components: regulator and scheduler Example: token bucket with fair queuing



IntServ/RSVP

IntServ/RSVP vs DiffServ

BB BB

DiffServ

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 2011 cs 414 – multimedia systems design lecture 22 – multimedia extensions to...

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