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Signaled Provisioning of the IP Network Resources Between the Media Gateways

in Mobile Networks

Leena Siivola

10.12.2004

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Problem Description

• For circuit switched (CS) traffic the delay and the jitter requirements are strict. That is why the amount of voice calls must be controlled not only from radio networks (RN) side but also from IP multiservice backbone’s point of view.

• The backbone edge nodes, i.e. the Media Gateway, must have ways to control the amount of traffic injected to the network– This must make it possible to give some QoS guarantees for the

voice calls– The network resources will be used more efficiently

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Objectives and Scope

• The objective of this Thesis is to

– describe the current Call Admission Control (CAC) mechanisms in the 3G IP multiservice backbone

– to evaluate the suitability of the NSIS signaling protocol framework for the CAC solution.

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The functional architecture of the 3G network

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The Call Admission Control Mechanism

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Provisioning Methods in the IP Multiservice Backbone

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MBAC = Measurement Based Admission ControlMPLS = Multiprotocol Label Switching

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Static Provisioning Methods in the Media Gateway

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Signaled Provisioning

Signaled provisioning is a tempting approach for CAC because it can give ’hard’ QoS guarantees for traffic flows and it can increase the network utilization.

Many QoS signaling protocols exist:• Tenet & ST-II• RSVP with its extensions• YESSIR (Yet another Sender Session Internet Reservations)• Boomerang

RSVP has been the most famous one• Has said to bee too complex and suffering scalability problems-> also other simulation results exist!

The work with the NSIS signaling protocol framework was started, because there was a need for a more lightweight signaling protocol.

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The NSIS Signaling Framework

NSLP = NSIS Signaling Application LevelNTLP = NSIS Transport Level

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The NSIS Signaling for Quality of Service (QoS)

The NSIS QoS signaling framework is based on a two layered architecture:

• NTLP (NSIS Transport Layer Protocol) • NSLP (NSIS Signaling Layer Protocol)

• QoS Model that is being signalled (e.g. Intserv or RMD)

• NSIS without QoS Model is only a framework with many optional features.

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Comparison Between the NSIS QoS Signaling and RSVP

• NSIS can be both sender- and receiver-oriented• NSIS does not support multicast• Mobility support• Bi-directional reservation possible

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NSIS(RMD) ArchitectureIt is not possible to evaluate the NSIS signaling without taking the QoS model into account. The NSIS framework consists of several optional features that can be taken into use.

• Resource Management in Diffserv (RMD) implemented with NSIS

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Successful Reservation

Initiator ReceiverEdge EdgeInterior Interior

Resv(QSpec)

Resv(E2E ignore, QSpec)

Resv(QSpec)

Resv(LQSpec)

Resv(LQSpec) Resv(LQSpec)

ResponseResponse

Response

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One Possible Implementation of NSIS to the 3G

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Evaluation

+ NSIS framework is flexible and modular

-> it can be used in different ways

+ There are several optional features that can be taken into use

- The resulting QoS protocol is even more complex than RSVP

-> what do we gain with the abstraction level?

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Evaluation: The NSIS(RMD) Implementation as an Example

• Evaluation criteriors:– Per-hop Performance Metrics

• Signaling message processing delay – Per-Reservation Performance Metrics

• Signaling Bandwidth Overhead• Abortive Provisioning• Blocking Probability• Reservation Setup Time

– Applicability of the NSIS(RMD) Signaling to the IP Multiservice Backbone

SCALABILITY AND ROBUSTNESS

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Per-hop Performance Metrics:

Signaling message processing delay

• ts = signaling message processing delay

• tS0 = the base parameter

• fR = a component dependent of the session load (LR)

• fT = a component dependent of the session (LR) and the signaling load (LT)

Signaling message processing delay

In the edge routers: proportional to the number of sessions

In the core routers: a constant

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Per-Reservation Performance Metrics:

Signaling Bandwidth Overhead

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Per-Reservation Performance Metrics:

Abortive Provisioning

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Per-Reservation Performance Metrics:

Blocking Probability

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Per-Reservation Performance Metrics:

Reservation Setup Time

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Conclusions

•The Intserv type (RSVP-like) per-flow end-to-end signaling brings nothing new when comparing to RSVP

• The message processing times have been estimated to be approximately same (1 ms)

• In the IP multiservice backbones some Intserv over DiffServ approach, such as RMD, could be the solution

• The message processing time in the core routers is approximately 5 microsec.• The system bottleneck is the signaling load on the edge routers

• There’s only approximately 0,9 msec time to process one reservation message in the edge router

• The link utilization is the same than with per-flow reservations• The response time is lower because of the sender-oriented approach

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Conclusions (continued)

• NSIS in itself has failed to meet its design criteria:• It is not simple and ligthweight -> It is too modular• There is a serious risk that NSIS will become only one signaling

protocol amoung others

• Too much politics involved in the protocol design work

• The router vendors are not actively participating the work -> the possibility to implement NSIS in networks is dependent of the router implementation

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Future research

• Router vendors’ interests• NSIS(RMD) / RSVP(RMD) with MPLS-tunnels• DCCP -> the adjustment of voice codecs with network

congestion, ECN marking

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THANK YOU!

• Any questions?

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ADDITIONAL INFORMATION

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Dynamic Provisioning Methods in the Media Gateway

• Measurement Based Admission Control (MBAC)+ CAC is fast+ no extra signaling load+ implementation costs low- cannot guarantee anything- the measurement result arrives always too late

• Probing+ no actual traffic will be lost- additional traffic -> the probe packets can overload the network- Setup delay - the routers do not support ?

• Bandwidth Broker (BB)+ high utilization- complex new node in the network

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RSVP vs. RMD PerformanceRSVP NSIS (RMD)

Response time

(bi-directional)

1 – 1.5 RTT 0.5 – 1 RTT

Processing time < 1 ms Edge: < 1ms

Int.: < 5 s

Link utilization ~100% ~100%

Scalability limited yes

Cost High processing capacity is required in

each nodes

Edge nodes: same as for RSVP

Int. nodes: simple functionality

Source: A. Bader et al.:Presentation in the 11th International Telecommunications Network Strategy and Planning Symposium (Networks2004)