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Static Call Admission Control and Dimensioning of Media Gateways in IP based Mobile Core Networks Mika Isosaari Supervisor: prof Jorma Virtamo Instructor: Harri Lehtomäki, M.Sc.
Slide titleIn CAPITALS
50 pt
Slide subtitle 32 pt
Static Call Admission Control and Dimensioning of Media Gateways in IP based Mobile Core
Networks Mika Isosaari
Supervisor: prof Jorma Virtamo
Instructor: Harri Lehtomäki, M.Sc.
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Slide title 40 pt
Slide subtitle 24 pt
Text 24 pt
Bullets level 2-520 pt
© Ericsson AB 2005 2005-08-032
Contents
Introduction General Structure of UMTS Release 5 Network Media Gateway Multiservice IP Transport Network Network Dimensioning Quality of Service Mechanisms to Guarantee QoS Static Admission Control Simulations Conclutions and Future Work
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Text 24 pt
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© Ericsson AB 2005 2005-08-033
Introduction
Background– VoIP vs. ToIP– How telecom grade speech can be transferred in
connectionless IP network?– Multiservice IP network: speech only one of the services
Objectives– To study how circuit-switched speech can be transferred in
an IP multiservice network so that a certain Quality of Service (QoS) level can be sustained
– How static admission control methods work and what is their influence on network dimensioning
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© Ericsson AB 2005 2005-08-034
Research methods
Literature study– ITU, 3GPP, IETF recommendation and specifications– Books and articles to get a more comprehensive picture of
the subject
Numerical evaluation– Used in comparing different static admission control
methods and their effect on dimensioning
Simulations– Show how the traffic intensity affects the utilization and
resource demand
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© Ericsson AB 2005 2005-08-035
General Structure of UMTS Release 5 Network
Three domains: Circuit-Switched (CS), Packet-Switched (PS) and IP Multimedia Subsystem (IMS)
– This thesis focuses on CS domain
Applications & Services
UTRAN
GERAN
MGW MGW
MSC server GMSC serverNc
Nb
Mc Mc
HLR
PSTN / Legacy / ExternalIu
A/ Iu
A/ Iu
CAP DC Signalling Interface
Signalling and Data Transfer Interface
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© Ericsson AB 2005 2005-08-036
Layered Architecture
Application layer Network control layer Connectivity layer
– MGW– Backbone
Transport Network
Network Control Layer
Application Layer
TSCServer
MSCServer
SCS
SGW
GERAN
ISDN/PSTN
Internet /Intranets
PLMN
HSS
SGW
Signalling
User Plane
UTRAN
GCP
Connectivity Layer
GMSCServer
APIs
MGW
MGW MGW
MGWAccess Networks External NetworksTransport Network
Network Control Layer
Application Layer
TSCServer
MSCServer
SCS
SGWSGW
GERAN
ISDN/PSTN
Internet /Intranets
PLMN
HSS
SGWSGW
Signalling
User Plane
UTRAN
GCP
Connectivity Layer
GMSCServer
APIs
MGW
MGW MGW
MGWAccess Networks External Networks
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© Ericsson AB 2005 2005-08-037
Media Gateway
PSTN/PLMN transport termination point May support media conversion, bearer control and
payload processing (e.g. transcoders and echo cancellers)
Nb User Plane traffic between MGWs is transported either over ATM or IP bearer
Logically resides at the border of the backbone, physically part of site configuration
Basic site infrastructure: Local Area Network (LAN) switches and site routers
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Multiservice IP Transport Network
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© Ericsson AB 2005 2005-08-039
Telephony services in multiservice IP network
Strict requirements for Telephony over IP (ToIP)– when international telecommunication networks interwork
with IP-based networks, the QoS experienced by the users should, as far as practicable, be the same as if there had been no interworking involved
Data Conversions and Protocols– MPLS, IP/UDP/RTP/NbUP, AMR/PCM…
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Network Dimensioning
The whole planning process is influenced by the UMTS architecture and IP backbone when compared to traditional GSM network
– overall architecture is very different– multiservice network– information is transferred in a form of packets in a
connectionless network Dimensioning Challenges
– every traffic flow has an effect on all the other traffic flows and a wrongly configured service can lead to degradation of speech quality, which is not acceptable
– when the speech is packet-based everything comes in practice a matter of probabilities
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© Ericsson AB 2005 2005-08-0311
Quality of Service
Quality of Service (QoS) is the quality of a requested service as perceived by the customer and always meant end-to-end
Information Quality Parameters: delay, jitter, BER, PLR, data rate
QoS Architecture in UMTS Networks vs. QoS in Internet– Mapping of different quality classes important– E.g. with DiffServ: EF conversational, AF streaming /
interactive, BE background Internet QoS: IntServ, DiffServ, MPLS(?), traffic
engineering
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© Ericsson AB 2005 2005-08-0312
Mechanisms to Guarantee Quality of Service
Network Level Mechanisms– Dimensioning– Overprovisioning– Architecture
Flow Level Mechanisms– Static Admission Control– Dynamic Admission Control
Packet Level Mechanisms AdmissionControl
StaticAdmissionControl
DynamicAdmissionControl
Pipe Model
Domain Model
Hose Model
MBAC ProbingBandwidth
BrokerSignalled
Provisioning
AdmissionControl
StaticAdmissionControl
DynamicAdmissionControl
Pipe Model
Domain Model
Hose Model
MBAC ProbingBandwidth
BrokerSignalled
Provisioning
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Static Admission Control
Basic idea: permanently allocated resources in the backbone network set by the service provider
MGW is in practice the most logical choice in the CN for the implementation (may work together with routers in the backbone)
Main advantage of static methods is their simplicity Downside is the inefficient usage of network resources Two most important models: pipe model and hose
model
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Static Admission Control
Pipe model– traditional model how provisioning has been performed in
private networks– point-to-point connection with a given pre-allocated capacity– destination-specific: large number of configuration
parameters– Implementation: MGW or MGW / edge router
Hose model– first proposed as a flexible model for resource provisioning in
VPNs– no individual pipes between nodes but “hoses”, which
contain all incoming or outgoing traffic– Advantages: flexibility, ease of specification, multiplexing
gain and characterization
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© Ericsson AB 2005 2005-08-0315
Simulations
What is the actual gain of statistical multiplexing when the traffic is handled as an aggregate rather than as individual pipes?
Simulations were performed with the NS2 network simulator
– PCM: CBR UDP application– AMR: two Exp on/off UDP apps. N1
N2
R DAccesslink
Core link
N1
N2
R DAccesslink
Core link
PCM AMR/speech AMR/silence
Packet size (bytes) 91 82 56
Sending interval (ms) 5 20 160
Sending data rate (kbps) 145,6 32,8 2,8
Average on/off times (ms) - 600/400 400/600
Average call duration (s) 90 90 90
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© Ericsson AB 2005 2005-08-0316
Simulations - results
101
102
103
104
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Total traffic intensity / Erl
Util
iza
tion
/ %
0% PCM10% PCM33% PCM
Bandwidth limit for link
– PLR 10-4
– Jitter <5ms
Utilization: gained link bw divided with average bw
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Simulations - results
5000 5200 5400 5600 5800 6000 6200 6400 6600 6800 7000500
1000
150050 Erl
5000 5200 5400 5600 5800 6000 6200 6400 6600 6800 70000.9
1
1.1
1.2x 10
4
Ban
dwid
th /
kbp
s
500 Erl
5000 5200 5400 5600 5800 6000 6200 6400 6600 6800 70001
1.02
1.04
1.06
1.08x 10
5
time / s
5000 Erl
34%
13%
3%
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© Ericsson AB 2005 2005-08-0318
Conclusions
Although various mechanisms exist for guaranteeing some QoS level in an IP network there is no particular mechanism that alone could sustain a certain QoS available mechanisms should be used together so that different mechanisms on packet, flow, and network level complement each other
Justifies also the use of static admission control methods, with which a permanent limit can be set for the traffic that a site can offer to a backbone network
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© Ericsson AB 2005 2005-08-0319
Conclusions
Pipe vs. hose– flexibility and easy implementation are clearly
characteristics of the hose model– overprovisioning factor related to configuration parameters
can with high probability be kept under 2 for the hose model– simulations show clearly that the utilization improves when
the traffic intensity is increased, but…
Already 250 Erl traffic has utilization rate of ca. 80 %– gain is not necessarily that significant and does not alone
make a clear difference between the two models
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© Ericsson AB 2005 2005-08-0320
Future work
measurements from a real network are needed to validate any simulation results
edge router based pipe model dynamic resource allocation optimal routing method for the hose model domain model: combine best features from pipe and
hose models
Slide titleIn CAPITALS
50 pt
Slide subtitle 32 pt
Questions?
