1 © NOKIA

QoS and Mobility

Rajeev Koodli, Cedric Westphal

and Meghana Sahasrabude

Nokia Research Center

Mountain View, CA

2 © NOKIA

Overview

• Background

• Problem scope

• Current work

• Discussion

3 © NOKIA

The Mobile World

In the future, a major partof personal communication

- be it voice, data, images or video - will be wireless.

The personal mobile devicewill be the main medium and platform!

4 © NOKIA

Applications, platforms, connectivity

Music Bluetooth

Java

Symbian

MP-3

Games

E-money

Streaming

Images

Sync-ML

There will be an explosion of different optimized, personalized products

Location

Messaging

5 © NOKIA

Amount and Types of Mobile Content Will Explode in the Future

• Types of content: • 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.)

ImagesMMSs Audio/musicApplicationsVideoclips

6 © NOKIA

Applications and Platform Convergence

EntertainmentMusic, Games, Fun!

Voice/SMSCalling, Messaging

ImagingMultimedia Messaging

MediaWeb Content Consumption

CommunicatorBusiness Services

7 © NOKIA 2002

QoS and Mobility

•The challenge for us: how to provide appropriate Quality of Service to

applications on mobile devices.

8 © NOKIA

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

9 © NOKIA

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!

• 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

10 © NOKIA

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

11 © NOKIA

Path of a packet

Marker+PacketClassifier

Policy Input

Incomingpacket

To outputqueue

Police/Shape

Meter

12 © NOKIA

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

13 © NOKIA

Mobility..

• On some networks, link layer handles mobility to make subnet mobility transparent

• GPRS, UMTS

• Will consider mobility with IP address change in this talk

GGSN

SGSN

SGSN

PDP context activate

PDP Context Update

IP network

14 © NOKIA

Mobile IP

R1

R2

MN

CN

Internet

Visited domain

HA

MN: Mobile NodeHA: Home AgentCN: Correspondent Node

15 © NOKIA

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

16 © NOKIA

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

17 © NOKIA

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 ‘session-id’ in addition to the standard flow classifier

• nice analysis in draft-thomas-seamoby-rsvp-analysis

18 © NOKIA

End-to-end..

R1

R2

MN

CNSignaling, data

19 © NOKIA

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-qos-01.txt, IEEE Wireless BB Summit, 2001

• “QoS-Conditionalized Binding Update in Mobile IPv6”, draft-tkn-mobileip-qosbinding-mipv6-00.txt, A. Festag et al.

20 © NOKIA

End-to-end….

R1

R2

MN

CNSignaling, data

LMM domain

signaling

21 © NOKIA

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 layer-specific mechanisms

• During handover, • state is re-established by requiring the MN to re-

initiate signaling• state is transferred from an AR to another

22 © NOKIA

Access Link..

R1

R2

MN

CN

Access link signaling

Context Transfer

23 © NOKIA

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-seamoby-ct-03.txt

24 © NOKIA

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”, draft-westphal-seamoby-qos-relocate-00.txt

25 © NOKIA

Performance Improvement with QoS CT

Normalized Packet discarding

0

1

2

3

4

5

0 500 1000 1500

Load on the new Access Router in Kbps

Pa

cke

t d

isca

rd c

o-

eff

icie

nt without Context

Transfer

with Context Transfer

26 © NOKIA

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

27 © NOKIA

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 ?

• QoS accounting state transfer

28 © NOKIA

QUESTIONS??

http://people.nokia.net/~rajeev,~c

edric