Item 2005L A Rønningen

Reservation Model

• Pessimistic or Optimistic Approach

• 1-N Senders and 1-M Receivers

• Sender-oriented or Receiver-oriented

• Immediate or Advanced reservation (for future use)

• Centralized or Distributed

Reservation, genericSender-oriented, Single Sender and Single Receiver

QoS &ResourceManager

ResourceManager

Sender

ResourceManager

ResourceManager

QoS &ResourceManager

Receiver

Dataflow

1

2

3

45

67

8Networknode

Networknode

Networknode

Reservation of e.g.,link capacity

1 – 4 Reservation Request5 – 8 Reservation Response

Admission when all resources are reserved

Rejection and cancellationimmediately when resource is not available

QoS &ResourceManager

QoS &ResourceManager

ResourceManager

ResourceManager

ResourceManager

Reservation Protocol, generic

(URL, StreamID QoS req list)

(URL, StreamID QoS req list)

User(URL, StreamID QoS req list, de- allocate) (URL,

StreamID QoS req list, allocated)

1

4

5

8

User

RSVP – Resource Reservation Protocol

• The Essence of RSVP– Provides reservations for link capacities in

multicast trees– Is receiver-oriented

RSVP

• Path - Path message– Sent by senders to tell the routers where to

send Resv messages

• Resv - Reservation message– Sent by the receivers towards senders to

specify the wanted receiving data rate. Senders and routers reserve the corresponding link capacity. Follows the same route as Path

RSVP example

S 1

D 1

D 5D 4

D 3

D 2

R 1

R 3

R 2

S 2

R - R ou te rS - S enderD - D es tina tion , rece ive r

P a th m essage , da ta

R esv m essage

ITEM, 1nov00 Leif Arne Rønningen

RSVP

• Reservation styles– Wildcard-filter: Receiver wants to receive all flows

from all senders, the reserved link capacity shall be shared

– Fixed-filter: Receiver wants to receive from a group of senders, each with a reserved link capacity for each sender of the group

– Dynamic-filter: Receiver wants to receive from a group of senders, with a reserved link capacity for the group. Receiver can change the senders, new reservation of paths is not needed (just like switching TV channels)

RSVP – Filters

fixed

Wild-card dynamic

Error Control

• Human Perception– Too low quality, Temp. loss of data

• Decompression Technology– Packet loss critical for synch

• Data Integrity– Errors in stored material, less acceptable than

a non-reproduceable data error

Error Detection

• System and transport layer may detect errors, but let the application layer take action

Error Correction

• Retransmission, acknowledgement

• Window flow- and error control

• Go-back-N Retransmission

• Selective Retransmission

• Can be applied for control-type of data, but

• Non of the above are suitable for real-time multimedia content!

Error Correction

• Partially Reliable Streams– Only the last n packets of the stream in a certain time

intervall will be retransmitted (n given by the timing contraints of the application and the network reliability)

• Forward Error Correction – FEC– N check bits added to the original S bits of data– Code efficiency, R = S/(S +N)– Can correct up to a certain number of errors– Low delay, hardware

Error Correction

• Priority Channel Coding– Packet streams are given different priorities,

and during congestion, low-priority packets are dropped first

– Example, in MPEG-2, I and P frames may be given higher priority than B frames

• Slack Automatic Repeat ReQuest (read)

QoS and Resource Monitoring

• Part of Resource Management• Ensure that QoS requirements are

satisfied• Measurements in Network and at end-

points• Measured data stored in Data Base• Calculation and presentation of

measurements• Connected to maintenance system

QoS Renegotiation

• User Request for Renegotiation

• Host System Request for Renegotiation

• Network Request for Renegotiation

QoS Adaptation

• Network Adaptation– Load balancing

• Load balancing control• QoS routing• Dynamic rerouting• Performance monitoring

QoS Adaptation

• Source and Application Adaptation– Adapt source packet rate

• Feedback from measurements in the network• Keep bottleneck link queue at a constant length • Control theory (PID, prediction,,)

– Adapt source packet rate locally (queueing)

Graceful degradation of media content during congestion

QoS Management Architectures

• Many proposals (read)

• Example, Quality Shaping of DMP