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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
Shumon Huque

University of Pennsylvania


April 15th 2002 - NSF/ITR Scalable QoS Workshop

Some QoS Deployment Issues
university of pennsylvania network
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
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
magpi gigapop cont
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
who wants qos
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
what types of qos
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?
  • 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
interdomain internet qos
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
interdomain internet2 qos
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
deployment challenges
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
deployment challenges 2
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
router support for qos
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
router code support cont
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
parallel network infrastucture
Parallel Network Infrastucture
  • Deploy parallel network infrastructure
  • Place QoS enabled routers on this
  • Researchers are happy, but ..
  • Cost prohibitive
qos policy issues
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
inter domain signalling
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
what we do today
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
bandwidth management alternatives
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
endstation problems
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
  • 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