3G SGSN Element Management 0 1

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3G SGSN Element Management


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COPYRIGHT INFORMATION

© Copyright Hughes Software Systems, 2004

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C o n t e nt s

1 . 3 G Wi r e l e s s N e t w o r ks 51.1. Management Modules 61.2. Challenges 71.3. 3G-SGSN Managers 81.4. Future Roadmap 81.5. Conclusion 91.6. References 9


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F i g ur es

F igur e 1 : The SGSN in the 3G N e twor k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5F i g u r e 2 : Man a g e m e n t o f a 3 G S GS N Mo d u l e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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1. 3 G Wireless NetworksServing GPRS Support Node (3G-SGSN) is

an integrated system consisting of severalmodules. 3G SGSN provides a framework forcomplete element management intended for afield-deployable system. The 3G-SGSN ElementManagement involves management of thesystem as well as its constituent modules. Thepaper summarizes element managementframework of 3G-SGSN. It also highlights thechallenges involved in development of theelement management framework and solutionsto various challenges faced

The 3G-SGSN is the network entity in a 3G GPRS

network primarily responsible for managing the

mobility of a served GPRS capable UE in the 3Gmobile network. It also performs session management

procedures for packet routing and transfer functions

and is responsible for the delivery of data packetsfrom and to the mobile stations within its geographical

service area.

The figure below gives an architectural overviewof a 3G network, illustrating the important

components of the network and the logical interfaces

between these components

PDN

Other PLMN

Uu

Um

GERANBTS

UTRAN

BTS

BSC

RNC

RNC

BTS

NB

NB

NB

Abis

Iub

Iur

SGSN

MSC

Gb

IuCS

IuPS

A

GGSN

GMSC

PSTN

E

Gn Gi

HLR/AUC

Gf

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OtherSGSN

OtherMSC

BorderGateway

BG GSNGp

Gn

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SMSGateway

SM-SC

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Figure 1: The SGSN in the 3G Network


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The system exports a public-interface to the

external network for IP and SS7 connectivity on adistinguished system entity called System Controller.

The public interface for node management also

terminates on the System Controller. The 3G-SGSNarchitecture separates the signaling and the traffic

processing on other distinguished system entities

referred to as Signaling slots and Traffic slotsrespectively. The System Controller is also responsible

for controlling and managing different Signaling slots

and Traffic slots configured on the system.

Each slot consists of several modules, each

providing a definite functionality defined for 3G-SGSN.

These modules include protocol stacks and elementmanagement modules.

The management of 3G-SGSN includes the

following functions

� Read configuration parameters of the 3G-SGSN at

startup.

� Modify configuration parameters of the 3G-SGSN

and handle consequent modifications in

operation.

� Read status values and tables of the 3G-SGSN.

� Retrieve (and possibly atomically reset) statistics

data collected at the 3G-SGSN.

� Report alarm conditions asynchronously.

� Detect faults and take necessary corrective

actions.

� Accept and perform imperative commands.

The basic principle here is that the public element

management interface will be accessible from thesystem controller through a proprietary suite of APIs

based on OIDs generated from SMIv2C MIBs.

Internally, each management function is available atthe system level as well as on individual slots.

1.1. Management ModulesThis section describes the various management

modules of 3G-SGSN.

1.1.1. Configuration Manager (CM)

The CM reads the configuration parameters of the

3G-SGSN from a configuration file at the startup and

configures the system and the correspondingmodules. At the system level it is also responsible to

serve the configuration requests received from an

external manager and configures the various modulesappropriately. Additionally the CM is also responsible

to serve requests from the external manager for

statistics collection, status query and trigger necessaryactions based on imperative commands received from

the external manager.

1.1.2. Health Manager (HM)

The HM periodically monitors the health status of

various modules in the system and in case of failure

reports the faults to a fault manager. This module isalso responsible to report startup of different slots

configured on the 3G-SGSN to FM.

1.1.3. Fault Manager (FM)

Any fault in the system is reported to the FM. TheFM takes necessary actions depending on the severity

of the fault. The different levels of severity identified

for the faults reported are Critical, Major, Minor andInformational. The Critical faults trigger a restart of

the system. All the faults that occur in the system are

further reported to the Event Manager.

1.1.4. Event Manager (EM)

The EM receives information for various events

and alarms that have occurred in the system from therespective modules or the FM. All the events and

alarms are reported to the configured external

element manager.

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1.2. Challenges3G-SGSN consists of several modules, which have

been developed independently. All these modules

individually export different APIs towards the

management interface. The biggest challengeinvolved in managing the 3G-SGSN and its modules,

was to address these several disjoint management

APIs through a common management point.

To address this mammoth management task a

uniform interface has been used to manage all the

modules irrespective of the APIs exported by them.The API interface for 3G-SGSN management has also

been adaptable enough to suite a standard

management technique. This has been achieved usingthe MIBs defined for the 3G-SGSN system as well as

all the constituent modules. Hence the management

interface is completely based on these MIBs.

1.2.1. Management Interface of 3G-SGSN

The MIBs defined for 3G-SGSN and its constituent

modules provided unique OIDs for each management

attribute. Internally 3G-SGSN addresses these OIDsfrom the level of 3G-SGSN OID. Hence it is possible to

modify the MIBs to generate OIDs for any network in

which the OIDs for any management attribute belowthe level of 3G-SGSN OID did not change.

Example:

The PLMN Id attribute of GMM module MIB in the3G-SGSN has the OID 1.3.6.1.4.1.303.1.1.1.1.1.7

defined for a 3G-SGSN with its MIBs defined for HSS

(OID 1.3.6.1.4.1.303). Internally 3G-SGSN processesthe OID after the prefix OID for HSS

(1.3.6.1.4.1.303). If this MIB is later defined for any

other network the prefix (1.3.6.1.4.1.303) can changebut the suffix (1.1.1.1.1.7) will remain unchanged.

Hence there is no change required in the

management functionality of 3G-SGSN when placed ina different network.

The stripping-off of the prefix OID digits isexternal to 3G-SGSN.

3G-SGSN management API is defined for a basicset of following 5 commands

� Set Request – This API corresponds to any

request received to set a particular management

attribute to a particular value.

� Set Response – This API contains the response to

the corresponding Set Request received indicating

a success or failure. In case of success the value

configured is also present in the API.

� Get Request– This API corresponds to any

request received to receive the value

corresponding to a particular management

attribute.

� Get Response– This API contains the response to

the corresponding Get Request received

indicating a success or failure. In case of success

the value is also present in the API.

� Trap – This API is used to asynchronously report

occurrence of any event or alarm in the 3G-SGSN.

All the management attributes are identified bytheir OIDs in the above APIs. Hence the management

interface is independent of the API expected by the

corresponding modules. Each module has a smallencapsulation layer which translates these generic

APIs (based on OIDs) to the module specific APIs and

vice-versa. This ensures that any changes in themodule specific management APIs require minimal

change in the 3G-SGSN management modules.

The Iu interface is split into 2 parts: circuitswitched and packet-switched. The Iu interface is

based on ATM with voice traffic embedded on virtual

circuits using AAL2 technology and IP-over-ATM fordata traffic using AAL5 technology. These traffic types

are switched independently to either 3G SGSN for

data or 3G MSC for voice.


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CoreModule

Porting Code of moduleincludes stack wrapper

Stack Wrapper Code

Module Specific API

Generic API

Figure 2: Management of a 3G SGSN Module

1.2.2. Management Information Base

As stated earlier the MIBs defined for 3G-SGSN

and its constituent modules generate unique OID

corresponding to each attribute. The leading digits ofthe attributes OID (prefix stripped-off) identify the

module for which the API is received. The

corresponding management module then routes themessage, unchanged, to the module using the 3G-

SGSN IPC. This ensures that any change in the MIB

specific to a module does not impact the operation ofthe management modules. However in case of

addition of new module minimal change is required in

the management modules to enable the managementof the new modules.

1.3. 3G-SGSN Managers1.3.1. SNMP Management

3G-SGSN can be bundled with a SNMP Agent,which exports the SNMP interface to the external

manager and the 3G-SGSN specific management API

towards the 3G-SGSN. The SNMP Agent is responsibleto strip off the prefix OIDs, which are specific to the

network.

1.3.2. CLI

3G-SGSN is available with a CLI (generated from

HSS CLI Toolkit). CLI is based on the 3G-SGSN

System MIBs and MIBs of the constituent modules of3G-SGSN. Corresponding to each MIB attribute the

CLI provides basic set of commands to configure the

attribute or retrieve its value from the system. CLIexports a telnet interface using, which the 3G-SGSN

can be managed remotely.

1.4. Future RoadmapCurrently 3G-SGSN supports a single

management interface, thus limiting the management

from a single external manager. In future 3G-SGSN

shall be enhanced to support management frommultiple managers simultaneously.

HSS FlexNM™ shall be available to manage the

3G-SGSN over the SNMP interface through the SNMPAgent.

Currently MIBs are defined for 3G-SGSN system

parameters and individual MIBs are defined for eachof the constituent module of 3G-SGSN. Some of the

modules’ MIBs have the same parameter hence

requiring multiple configuration of the same attribute

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for the system. A proxy MIB will be defined for 3G-SGSN, which shall require a single configuration for

such attributes and internally 3G-SGSN management

modules can configure appropriate modules based onthe module specific MIBs.

1.5. ConclusionElement management system of HSS 3G SGSN

provides a uniform management interface of all theintegrated stack components. Being MIB based NM

interface, this can be adapted to interface with a

standard NM framework

1.6. References� HSS Internal Approach Papers for 3G-SGSN

Feature Development

� IETF RFC 1157 Simple Network Management

Protocol (SNMP). J.D. Case, M. Fedor, M.L.

Schoffstall, J. Davin. May-01-1990.

� 3GPP TS 32.106, 3G Configuration Management:

Concepts and Requirements

� 3GPP TS 32.111-1, 3G Fault Management

Architecture

� ITU-T Recommendation X.733, Alarm Reporting

Function

E-mail: info@h

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