Integrated Services in the Internet Architecture: an Overview

1
Integrated Services in the Internet Architecture
an Overview

• RFC 1633
• R. Braden, D. Clark, S. Shenker
• June 1994

2
Introduction

• proposed extension to the Internet architecture
• protocols to provide integrated services
• Realtime feature is needed.
• Cheep multimedia HW, IP multicasting and
  Highly-sophisticated digital AV application

3
Elements of the Architecture

• Integrated Services Model
• Guaranteed and Predictive Service
• Assumption
• resources must be explicitly managed in order to
  meet application requirements ("resource
  reservation" and "admission control" )
• it is desirable to use the Internet as a common
  infrastructure to support both non- real-time and
  real-time communication.

4
Reference Implementation Framework

• packet scheduler, the admission control routine,
  the classifier, and the reservation setup
  protocol
• Packet scheduler
• Manages the forwarding of different packet
  streams
• Classifier
• each incoming packet must be mapped into some
  class
• classification may be based upon the contents of
  the existing packet header and/or some
  classification number

5
Reference Implementation Framework

• Admission Control
• invoked at each node to make a local
  accept/reject decision, at the time a host
  requests a real-time service
• Reservation setup protocol (RSVP)

6
Integrated Services Model

• Quality of Service Requirements
• Real-Time Application
• Playback application
• the value of the offset delay determines the
  latency of the application
• the delays of individual packets can decrease the
  fidelity of the playback by exceeding the offset
  delay
• Intolerant and tolerant application
• Intolerant applications must use a fixed offset
  delay and be characterized Guaranteed service
• tolerant applications reduce their latency by
  varying their offset delays in response to the
  actual packet delays and is provided by
  Predictive service
• traffic characterization and admission control
  are necessary

7
Quality of Service Requirements

• Elastic Applications
• Elastic applications will always wait for data to
  arrive.
• To provide ASAP service
• Uses the arriving data immediately, rather than
  buffering it
• Not subject to admission control.

8
Resource-Sharing Requirements and Service Models

• Link Sharing service model
• Multi-entity link-sharing.
• Multi-protocol link-sharing
• Multi-service sharing
• Admission control will be necessary to ensure
  that the link-sharing commitments can be met.

9
Packet Dropping and Reservation Model

• "preemptable" packet service
• discarding preemptable packets
• "expendable" packets
• "reservation model"
• how an application negotiates for a QoS level

10
Traffic Control Mechanism

• Basic Functions
• Packet Scheduling
• to reorder the output queue
• Priority scheme, Round-Robin, Weighted Fair
  Queueing
• Packet Dropping
• taken by TCP to improve congestion control
• dropping and scheduling must be coordinated.
• Packet Classification
• complexity and processing overhead.
• Admission Control
• Decision about resource availability
• Router vendor.

11
Applying the Mechanism

• Guaranteed delay bounds
• if the router implements a WFQ scheduling
  discipline, and if the nature of the traffic
  source can be characterized then there will be an
  absolute upper bound on the network delay of the
  traffic
• Link sharing
• WFQ scheme
• Predictive real-time service
• WFQ do not always lead to low bound of delay
• Two tier algorithm is needed.
• first tier separates traffic which has different
  service objectives, and the second tier schedules
  traffic within each first tier class in order to
  meet its service objective

12
An example The CSZ scheme

• a code package has been implemented which
  realizes the services
• WFQ used
• Guaranteed service gets the highest priority
• Predictive service and best effort service are
  separated by priority
• Within the best-effort class, WFQ is used to
  provide link sharing

13
Reservation Setup Protocol

• RSVP overview
• Reservation Styles
• wildcard, fixed-filter and dynamic- filter
• wildcard
• not source-specific, so all packets destined for
  the associated destination (session) may use a
  common pool of reserved resources.
• fixed-filter
• cannot be changed during its lifetime without
  re-invoking admission control
• Dynamic-filter
• allow a receiver to modify its choice of
  source(s) over time without additional admission
  control

14
Reservation Setup Protocol

• Receiver Initiation
• RSVP uses receiver-initiation of reservations
• Soft State
• Hard State(HS) approach (also called
  "connection-oriented"), and the Soft State(SS)
  approach (also called "connectionless")
• RSVP takes the SS approach.
• reservation state is periodically refreshed by
  the end hosts
• simplicity and robustness

15
Routing and Reservations

• When a route changes, there must be some
  mechanism to set up a reservation along the new
  route.
• four issues
• Find a route that supports resource reservation
• Find a route that has sufficient unreserved
  capacity for a new flow
• Adapt to a route failure
• Adapt to a route change (without failure)
• Route pinning