Transcript QoS and Mobility in IP Networks

QoS and Mobility
Rajeev Koodli, Cedric Westphal
and Meghana Sahasrabude
Nokia Research Center
Mountain View, CA
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Overview
• Background
• Problem scope
• Current work
• Discussion
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The Mobile World
In the future, a major part
of personal communication
- be it voice, data, images or video will be wireless.
The personal mobile device
will be the main medium and platform!
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Applications, platforms, connectivity
Games
Symbian
Images
Java
Location
Sync-ML
Messaging
Streaming
MP-3
Music
Bluetooth
E-money
There will be an explosion of different
optimized, personalized products
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Amount and Types of Mobile Content Will
Explode in the Future
MMSs
Images
Videoclips
Audio/music Applications
• Types of content:
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• User created
(images, videoclips, music etc.)
• Personal
(music, movies, movieclips, games,
applications, etc.)
• Group
(family, friends, daughter's soccer team etc.)
• Community
(greyhound owners' image album etc.)
• Subscribed
(Manchester United Multimedia news
service etc.)
• Network provided
(location-based weather info etc.)
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Applications and Platform Convergence
Voice/SMS
Calling, Messaging
Entertainment
Music, Games, Fun!
Imaging
Multimedia Messaging
Media
Web Content Consumption
Communicator
Business Services
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QoS and Mobility
• The challenge for us: how to
provide appropriate Quality of
Service to applications on
mobile devices.
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QoS and Mobility
• Pessimist’s view
• Lots of literature, little understanding
• Combine the two, there is even more confusion!
• On the other hand,
• the relative merits are better understood
• QoS is mostly Connection Admission Control (CAC) and
Scheduling problem (transport issues)
• Mobility is a routing problem
• So, transport and routing interplay opens up new issues
• We will consider the two separately first
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QoS
• How do you provide desirable treatment for certain flows (as
opposed to others) ?
• Connection Admission Control decides whether resources can
be provided without affecting existing flows
• generally a hard problem: flow models, flow aggregation,
end-to-end resource admission issues
• SLAs are typically used for exchanging traffic across
operator domains; intra-domain CAC is the domain’s
problem!
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• Scheduling ensures that packet treatment (Per-Hop Behavior
or PHB) is according to the admitted parameters
• multiple well-known scheduling algorithms, WFQ, WF2Q,
DRR, CSFQ
• most vendors support multi-class queues
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QoS...
• What does QoS entail then ?
• Classify an incoming packet
• Meter (if needed)
• (Re)Mark the packet for appropriate treatment
• schedule packet for transmission
• means state at a router
• Intserv requires all Intserv-compliant nodes on the end-to-end
path to have (soft) state and update it via periodic refresh
messages
• signaling (e.g., RSVP) necessary
• Diffserv moves all state to the edge while leaving core routers
to provide PHBs based on Behavior Aggregates
• signaling may be necessary at the edge
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Path of a packet
Incoming
packet
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Marker
Meter
Police/
Shape
Policy Input
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+
Packet
Classifier
To output
queue
Mobility
• How to allow transport protocols to use a “fixed” IP address
while the device changes subnets ?
• IP address never changes despite movement across subnets
• burden on the network to route packets to topologically
inconsistent addresses (host based routing)
• ad hoc network routing is based on host routing
• IP address changes when subnet prefix changes
• burden on the Mobile Node (MN) to ensure it receives
packets; normal prefix-based routing
• mobile ip requires a MN to update its home network router
(actually a Home Agent) to receive packets
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Mobility..
• On some networks, link layer handles mobility to make subnet
mobility transparent
• GPRS, UMTS
PDP context activate
SGSN
IP network
GGSN
SGSN
PDP Context Update
• Will consider mobility with IP address change in this talk
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Mobile IP
HA
MN
CN
R1
R2
Visited domain
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Internet
MN: Mobile Node
HA: Home Agent
CN: Correspondent Node
Mobility...
• So, what does mobility involve ?
• The MN should detect that it has moved to a new subnet
• typically done through router advertisements
• fast handovers allow a MN to be notified a priori
• MN must configure a new topologically correct IP address
• Inform its home network agent about its new co-ordinates
• The MN may directly inform its correspondent nodes
• There is connectivity latency and route update latency
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QoS and Mobility problem
• Since QoS implies state at a router and mobility means routing
path change, how is the QoS state re-established due to
mobility ?
• Possible approaches to solving the problem
• End-to-end state re-establishment (for Intserv)
• Only access link state re-establishment (for Diffserv)
• hybrid of the above two
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End-to-end state re-establishment
• Needs signaling
• RSVP
• the most well-known end-to-end QoS signaling protocol
• mobility-unaware; does not necessarily know that handover
has happened
• latency before the messages are even sent
• mobility-blind; i.e, if an IP address changes, the flow is new
• end-to-end signaling
• admission control
• unable to make use of localized mobility management
• extensions possible; e.g., use Home Address or a ‘sessionid’ in addition to the standard flow classifier
• nice analysis in draft-thomas-seamoby-rsvp-analysis
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End-to-end..
MN
Signaling, data
R1
R2
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CN
End-to-end...
• Mobile IP extension
• when a MN configures a new IP address (due to handover),
it sends a Binding Update message to its Correspondent
Node
• provides a natural point to initiate QoS signaling
• piggyback on Binding Update
• fast initiation of signaling
• an existing flow needs to be identified by a mobility invariant attribute such
as a “session-id”, “flow-label”
• provides ability to make use of localized mobility
• signaling confined to nodes affected by mobility
• state re-use
• provides performance benefits compared to RSVP
• “A Framework for QoS Support in Mobile IPv6”, draft-chaskar-mobileip-qos01.txt, IEEE Wireless BB Summit, 2001
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• “QoS-Conditionalized Binding Update in Mobile IPv6”, draft-tkn-mobileipqosbinding-mipv6-00.txt, A. Festag et al.
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End-to-end….
MN
Signaling, data
R1
R2
signaling
LMM domain
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CN
Access Link state establishment
• An Access Router ensures that the flow entering into the
network is conformant
• The state at the AR may be by RSVP, ICMP or by link layerspecific mechanisms
• During handover,
• state is re-established by requiring the MN to re-initiate
signaling
• state is transferred from an AR to another
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Access Link..
Access link signaling
MN
CN
R1
R2
Context Transfer
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Context Transfer
• Mobile Nodes establish network state at their access routers
• AAA, QoS, Header Compression, IPSec
• State needs to be re-established at the new access router
• Transferring state during handovers
• saves signaling overhead over the air interface
• provides performance benefits for transport protocols
• makes handovers “seamless”
• “Fast Handovers and Context Transfers in Mobile Networks”, R. Koodli and
C. E. Perkins, ACM CCR, October 2001
• “A Context Transfer Protocol for Seamless Mobility”, draft-koodli-seamobyct-03.txt
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QoS CT
• QoS state established via access link signaling
• QoS context = {QoS Profile Type, QoS Profile}
• QPT = Diffserv, Intserv, Best-Effort
• QoS Profile = attribute values corresponding to a QPT
• packet classifier, meter, marker
• Link-specific Profile Types could also be defined
• “Context Relocation of QoS Parameters in IP Networks”, draftwestphal-seamoby-qos-relocate-00.txt
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Performance Improvement with QoS CT
Packet discard coefficient
Normalized Packet discarding
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4
3
without Context
Transfer
2
with Context Transfer
1
0
0
500
1000
1500
Load on the new Access Router
in Kbps
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CT and Signaling
• CT works when state is restricted to an access router (or a
single node)
• When state needs to be re-established along multiple nodes,
signaling is necessary
• CT across access routers and signaling upstream may be
useful
• saves air interface signaling overhead
• when accomplished “sufficiently in advance”, all the relevant
nodes could have the state
• end-to-end signaling not ideal for seamless handovers
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Open problems
• New router interface capability
dissemination
• extrapolating this at the previous router
?
• What should be the QoS given ?
• E.g., should TCP be allowed to
continue with the rate before handover
?
• QoS authorization during handovers; how
does the new router know it is allowed to
support QoS for the MN ?
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QUESTIONS??
http://people.nokia.net/~rajeev,~cedric
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