GPRS优化方法、案例培训资料(MOTO)

Sessions are described by: • Session Duration (D) • Session Inter-arrival time (I)
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D
I
t
Definition of A Burst
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Service Telephony: WWW: FTP: Email (download): SMS: Example of Burst Active talk spurt HTTP objects in a WWW page download Transfer of a file between server ↔ client A file containing single email with MIME encoded attachments One text message
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Burst Packet S
τ
T
A
PDP Contexts
A PDP context is a logical pipe that provides the transfer of user data across the UMTS network.
Bursts described by: • Burst Size/Duration (τ) • Inter-burst time (T)
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τ
T
t
Note: Burst duration may be driven by data size/link speed/load
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PDP Contexts vs. Sessions in USTM
A service session needs a connection across the IP networks to operate. Thus a service session needs a PDP context over UMTS for its duration. However, a PDP context may exist before and after a particular service session. More than one service session can use a single PDP context. Different services sessions may share a single PDP context. PDP contexts may change states (active, standby). This is transparent to the service.
1. GPRS业务模型分析 GPRS业务模型分析
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Motorola USTM View of User Services
USTM considers service activity from the GPRS/UMTS user’s point of view: (USTM stands for Unified Simple Traffic Models)
File bursts
Uplink
SMS MO:
Message Burst
Uransmission of the SMS packet.
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A complete View – Example: WWW Traffic Model
Page Downloads
WWW:
Downlink Complex WWW pages may contain multiple objects located on different servers. Downloading an object is an HTTP request/response transaction.
WWW Application Summary:
D I
t
Session Objects
UL
Bursts
DL
t t
D - Session duration I - Session inter-arrival time τ - Burst duration T - Inter-burst time S - Packet size A - Packet inter-arrival time
Layered Traffic Modelling Approach
The traffic characteristics of a service can be very complex. It is often described by a layered service workload model – data application model in USTM. The following is a view of the FTP service:
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Example: Application <-> Protocols Interaction <As the application interacts with different protocols in the network implementation, application traffic becomes packets.
Real Network
User LAN
MS Modem
GGSN
UMTS looks like an IP router
UMTS PDP
UE
Ext. IP
TE
=
TE TE
TE
Note: The PDP context does not really see the user application, but only sees the 2012年3月12日星期一 IP QoS requirements.
Session
t
Burst (File)
t
Packet
t
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Definition of A Session
A service session is a logical entity. Independent of transmission direction. It is basically described as the period where a user is actively using the service. During an active service session, the network must maintain connectivity between the users in that session.
More Examples of Burst
Telephony:
Speech bursts
Uplink Downlink
Speech samples encoded into speech frames. Whilst originator is talking, speech frame activity generates the speech burst.
The Burst represents a block of real traffic that the application sends/receives. The Burst is the activity that the bearer channels in the network see. For many services, a burst equates to the transfer of a file or message. The burst is uni-directional (uplink and downlink bursts are different).
UE Application
UMTS
PDP Context
External Network
Remote Host Application
From either end, the PDP context will look like an IP termination (IP address/port) that offers a given level of IP QoS (e.g. acts as a DiffServ code point).
Application-level Activity Packet Activity
Application Application
TCP/IP
UTRAN
Core Network Internet
UMTS Network
Packet behaviour may be different in different protocol layers, and parts of the network, i.e:
User Application User Application
Application Level Service Activity
Telecommunications Network
At this level the application service behaviour is relatively network implementation independent. However, as the traffic is transported over the network, traffic behaviour within the network will depend on the network implementation and configuration
Service Telephony: WWW: FTP: Email (download): Definition of Session Telephone call duration Web browsing session (difficult to determine finish) Period downloading from single server From connecting to email server to disconnection
• TCP & IP packets • RLC SDU • Radio frames
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• UTRAN • UMTS Core Network • External Packet Data Network