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Some QoS Deployment Issues

Shumon Huque University of Pennsylvania MAGPI GigaPoP April 15th 2002 - NSF/ITR Scalable QoS Workshop. Some QoS Deployment Issues. University of Pennsylvania network. Large research university in Philadelphia, PA 22,000 students, 4,000 faculty, 10,000 staff 48,000 registered IP addresses

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Some QoS Deployment Issues

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  1. Shumon Huque University of Pennsylvania MAGPI GigaPoP April 15th 2002 - NSF/ITR Scalable QoS Workshop Some QoS Deployment Issues

  2. University of Pennsylvania network • Large research university in Philadelphia, PA • 22,000 students, 4,000 faculty, 10,000 staff • 48,000 registered IP addresses • 200 switched subnets • Central routing between them and out to Internet and Internet2

  3. MAGPI GigaPoP • An Internet2 GigaPoP • Value added services • Commodity Internet transit • Facilitator of regional edu/research initiatives • Subscribers • UPENN, Lehigh U, Princeton U, PA county school units, J&J Pharmaceuticals

  4. MAGPI GigaPoP (cont) • External Connectivity • Internet2 • OC-12c POS to Abilene • Commodity Internet • UUNET: OC-3 • Cogent: Gigabit Ethernet • Yipes: Gigabit Ethernet (rate limited) • DCANet: Fast Ethernet

  5. Who wants QoS? • University researchers • QoS researchers in CS department • Research applications needing strict guarantees on latency, b/w, jitter etc • Networking staff (Univ and gigaPoP) • Manage exploding b/w needs • Enable new classes of applications • Eg. VoIP, video conferencing, streaming • Run non-mission critical traffic at lower priority • Eg. File sharing apps, dorm traffic, bulk transfers

  6. What types of QoS? • DiffServ in routing core and gigaPoP • Layer2 priority (802.1p) in the switched portions of the campus network • Mapping L3 QoS to/from L2 QoS • Signalling and admission control? • RSVP intra-domain? Aggregate reservations & map to Diffserv traffic class at edge? • Bandwidth Broker signalling?

  7. DiffServ • Types of forwarding behavior we are most interested in: • EF (Expedited Forwarding) • BE (Best Effort - default PHB) • LBE/Scavenger (eg. QBSS) • ABE - low delay form

  8. Interdomain Internet QoS • Not very optimistic • Some ISPs are starting to offer services • Multiplicity of providers • Need for them to run interoperable QoS implementations • Mechanisms to ask for QoS reservations across administrative domains • Peering/SLA issues

  9. Interdomain Internet2 QoS • More optimistic • Typically one or a few QoS enabled I2 backbone networks (eg. Abilene) • Agreed upon QoS architecture • Common set of operational practices and procedures • Some provisioning procedures in place • Existing demand from researchers

  10. Deployment Challenges • I2 backbone is an R&E network, but .. • Universities are using it to transport production traffic between them • And not just traffic associated with meritorious research applications (one of the original ideas) • GigaPoP is a production network providing access to I2 and Commodity Internet

  11. Deployment Challenges (2) • So, we need to be very careful about changes we introduce to the network to facilitate QoS • Don’t jeopardize existing production traffic

  12. Router support for QoS • Not mature or well tested • Often the features are in experimental code trains, unsuitable for deployment in a production network • Marking, re-marking, policing, traffic shaping, appropriate queue scheduling disciplines etc • Insufficient #queues to support large scale service differentiation • Often software implementations of required queueing disciplines instead of hardware • Obviously this situation will improve in the future

  13. Router code support (cont) • Example: Juniper routers • 4.x release: • Can police DS BA’s but not much more • 5.x release: • More queue scheduling disciplines • Per queue traffic shaping • DSCP marking and re-marking • DSCP based prioritization and forwarding • Eg. Assigning EF BA to a high priority queue • Mapping of 802.1p to Layer-3 QoS

  14. Parallel Network Infrastucture • Deploy parallel network infrastructure • Place QoS enabled routers on this • Researchers are happy, but .. • Cost prohibitive

  15. QoS policy issues • Where does marking occur? • Endstations • First hop routers or switches • Edge routers • Who’s allowed to mark? How to validate? • Complexity of deploying policies • Additional controls and checks to enforce the policies • Policy servers: COPS, bandwidth brokers etc

  16. Inter-domain signalling • No suitable mechanisms today for end2end inter-domain signalling of QoS reservations, call admission control • Manual/static provisioning • Bandwidth brokers/SIBBS work ongoing

  17. What we do today • To facilitate researchers doing wide-area QoS experimentation: • Conscious effort not to impede • Provide research labs with an uncongested path though campus/gigapop to QoS enabled Abilene network • Make sure intervening routers don’t mark or re-mark DSCP code points

  18. Abilene QoS testbed

  19. Bandwidth Management Alternatives • University has experienced rapidly increasing bandwidth requirements • Overprovision the campus network • Buy more commodity Internet bandwidth through the gigaPoP • Employ rate limiting where appropriate • Employ lightweight QoS, eg. LBE/Scavenger

  20. Endstation problems • Network apps often unable to use available bandwidth because of problems on end-stations: • Poorly designed applications, application protocols • Insufficiently sized socket buffers • Inefficient, insufficiently tuned network stacks • Duplex mismatch • MTU mismatch • Having QoS in the network does not address this class of performance problems

  21. Conclusion • We’re interested in QoS • Too early to deploy end2end reservation based QoS in many production networks • Intra-domain QoS a near-term possibility • Both reservation based and lightweight • VoIP, degrading non-mission critical traffic • End2End Inter-domain QoS difficult • Co-ordination, SLAs, inter-domain signalling

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