Quality of Service and Asynchronous Transfer Mode in IP - - PowerPoint PPT Presentation

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Quality of Service and Asynchronous Transfer Mode in IP - - PowerPoint PPT Presentation

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Quality of Service and Asynchronous Transfer Mode in IP Internetworks Bruce A. Mah bmah@CS.Berkeley.EDU The Tenet Group University of California at Berkeley T Y O I F S R C E A V A L I I F N O U R L L E E

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Quality of Service and Asynchronous Transfer Mode in IP Internetworks

Bruce A. Mah bmah@CS.Berkeley.EDU The Tenet Group University of California at Berkeley Qualifying Examination 23 November 1994

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Outline

Introduction Previous and Related Work Research Issues Research Plan Summary

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Introduction

Asynchronous Transfer Mode (ATM)

A new networking technology for integrated services networks

Internet Protocol (IP)

Network layer protocol of the Internet Communication over heterogeneous internetworks

IP over ATM

The use of an ATM network to transmit IP datagrams

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Asynchronous Transfer Mode (ATM)

Point-to-point links between switches in a switching fabric Connection-oriented network Potential for quality-of-service guarantees No specific QOS model implied or assumed

Possible to specify general delay, bandwidth, and loss requirements Some number of service classes H H H S S S S

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The Need for Internetworking

ATM is not (will not be?) ubiquitous and dominant

Time to deploy a new technology Legacy networks (e.g. Ethernet) New, non-ATM networks

An internetworking solution is still required

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The Internet Protocol (IP)

Supports heterogeneous internetworks Datagram-oriented network-layer protocol No performance guarantees or quality of service support

ATM AAL FDDI Ethernet IP UDP TCP

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Environment

Conventional data (e.g. ftp, telnet) as well as multimedia traffic (e.g. nv, vat)

R

ATM Network

H R R H FDDI Ethernet Ethernet S S S

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IP over ATM

Question: How can IP applications get the best performance

  • ut of an ATM subnet?

Idea: Use quality of service features of ATM to improve IP performance Different types of virtual circuits to meet needs of different applications

telnet ⇒ low latency bound Video playback ⇒ bandwidth guarantee

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Related Work

Models for IP over ATM

Conventional Model—RFC 1577 (1994) Subnet Model—R. Cole (1994) Connectionless Servers—D. Box, et al. (1993), D. Omundsen, et al. (1994)

Traffic Measurement and Analysis

  • A. Schmidt and R. Campbell (1993)

Traffic Multiplexing

  • R. Cáceres (1992)
  • K. Claffy (1994)

Virtual Circuit Management

  • C. Lund, et al. (1994)
  • S. Keshav, et al. (1994)
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Research Issues

The Use of ATM QOS for IP Conversations

How to map a stream of IP datagrams onto a virtual circuit? What performance requirements do IP conversations have?

Multiplexing

How and when should multiple conversations share a virtual circuit?

Virtual Circuit Management

When should virtual circuits be created? When should virtual circuits be torn down?

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Mapping IP Datagrams onto a Virtual Circuit

“IP Conversation”

A stream of related IP datagrams between common endpoints with some defi nable set of QOS parameters Hosts and routers place packets of IP conversations onto ATM VCs

Examples

All datagrams for a given TCP connection All datagrams between a pair of UDP ports All datagrams on an IP multicast tunnel All ICMP datagrams between a host pair

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Mapping IP Datagrams onto a Virtual Circuit

IP (and TCP, UDP, ICMP) headers to determine conversations

Version Hdr Ln Prec TOS Total Length ID Flags Fragment Offset TTL Protocol Header Checksum Source Address Destination Address Source Port Destination Port TCP Sequence Number TCP Acknowledgment Number Hdr Ln Rsrvd Flags Window Size TCP Checksum Urgent Pointer

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Determination of Requirements

Goal is not end-to-end performance guarantees, but improved performance across ATM subnet Well-known applications

For applications whose needs and traffi c characteristics ar e known Identifi ed by fi elds in upper -layer protocol headers Example: telnet

Monitoring traffi c

Adaptive algorithm for determining bandwidth requirements Long-lived conversations only Example: Video transmission with user adjustments

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Determination of Requirements

Explicit signalling

Disadvantage: needs support by application In-band (e.g. IP TOS/Precedence, IP options) Out-of-band with a signalling protocol (e.g. RCAP, RSVP)

Default requirements

For traffi c not cover ed by other means “Best effort”?

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Datagram to Virtual Circuit and QOS Mapping

R H H TCP/IP 128.32.33.103 (1024) 192.57.128.2 (23) UDP/IP 128.32.33.107 (2049) 198.51.254.130 (1201) Low delay VC for telnet High bitrate VC for NFS

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Multiplexing with QOS Considerations

Tradeoff

Protection of individual IP conversations Increased utilization of reserved resources due to statistical multiplexing

Levels of Multiplexing

Virtual circuit per router pair— Most commer cial ATM LANs Virtual circuit per host pair Virtual circuit per application per host pair—

  • R. Cácer es (1992)

Virtual circuit per IP conversation Combinations

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Virtual Circuit Per Router Pair

All traffi c between a pair of r outers routed over same virtual circuit Statistical multiplexing of conversations over virtual circuit No protection among conversations sharing a router pair Uses:

Low-bitrate or bursty traffi c (ICMP) Background best-effort traffi c (electr onic mail) R R H H H H

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Virtual Circuit Per Conversation

Each IP conversation seen by a router uses a separate virtual circuit IP conversations protected from each other over ATM subnet No statistical multiplexing gain within virtual circuit Uses:

Real-time video Interactive fi le transfer R R H H H H

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Virtual Circuit Management with QOS Considerations

Paradigm shift: ATM connections vs. IP datagrams

When to set up and tear down connections for datagrams?

Tradeoff

Resource reservation for QOS-guaranteed virtual circuits Connection setup latency

Alternatives

Permanent Virtual Circuits (PVCs) Switched Virtual Circuits (SVCs) Switched Virtual Circuits with connection caching Combinations

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Permanent Virtual Circuits

No connection setup latency Resources always reserved Scalability a problem: connections

R R R

O n2 ( )

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Switched Virtual Circuits

Determine start and end of IP conversations

First packet ⇒ start Timeout ⇒ end

Connection setup latency incurred

For fi rst packet of conversation For other packets if SVC closed too early

Enhancement: connection caching for other IP conversations

R R R

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Research Plan

Approach

Evaluate IP over ATM with QOS policies in an actual ATM network

Completed Work

Packet classifi er for XUNET II MBONE Measurements

Future Work

IP over QOS-guaranteed virtual circuits on XUNET Evaluation of policies

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Research Plan— Appr oach

Evaluate policies in an actual wide-area ATM network

Quality of service mapping Multiplexing Virtual circuit management

Implementation and Evaluation: XUNET II

A wide-area ATM backbone network ATM/DS3 connecting FDDI LANs IP over ATM service in place now (PVCs only)

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XUNET II Geographic Topology

Berkeley LBL Bell Labs Wisconsin UIUC LLNL SNL Rutgers

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XUNET II Logical Topology (IP Layer)

R R H H H FDDI Ethernet R R R R R R

XUNET ATM Subnet

Campus Network

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Completed Work— Packet Classifi er

XUNET IP driver modifi ed to discriminate among IP conversations

All TCP connections map to unique virtual circuits All UDP streams map to unique virtual circuits Aggregation of conversations possible No performance degradation observed

XUNET IP over ATM service enhanced to use SVCs

Virtual circuits created on demand Static timeout (15 seconds for initial testing)

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Completed Work— MBONE Measur ements

Traditional data applications (ftp, telnet) well-studied Little published about audio and video on Internet Traces taken of MBONE conversations

Video—nv Audio—vat Image distribution—imm

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Video Bitrate (nv 128 Kbps)

Peak bitrate (one-second samples) 270 Kbps

50 100 150 200 250 300 500 1000 1500 2000 2500 3000 3500 4000 KBits per second Time in Seconds law.cs.berkeley.edu

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Future Work

Obtain QOS-guaranteed virtual circuits over XUNET

Scheduling disciplines—

  • H. Saran, et al. (1993)

Signalling support—

  • S. Keshav (1994)

Formulate IP over ATM policies

Mapping from IP conversation(s) to QOS-guaranteed virtual circuit Multiplexing policy Virtual circuit setup and teardown policy

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Future Work

Experimental setup

Transmit IP traffi c fr om applications Vary intensity and type of cross traffi c Measure performance as seen by applications

Evaluate performance for IP conversations with respect to:

End-to-end latency Throughput Setup latency

Evaluate overall network performance with respect to:

Utilization Effi ciency and over head Best-effort performance

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Contributions

Policies and subpolicies for the transmission of IP datagrams

  • ver QOS-guaranteed ATM virtual circuits

QOS mapping Multiplexing Virtual circuit management

Criteria and a methodology for evaluating IP over ATM policies A working implementation of both a set of IP over ATM policies and any necessary underlying framework An evaluation of policies on a wide-area ATM network

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Summary

ATM will be incorporated into IP internetworks Issue: Can the use of QOS guarantees within an ATM subnet be benefi cial to IP applications?

Use of virtual circuits with QOS parameters to carry IP data Multiplexing Virtual circuit use and management

Evaluate policies on XUNET II, an experimental wide-area ATM network

Performance of individual conversations Performance of network as a whole