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CORBA based Network Management

By : Sudha MishraB. Tech. CSE 3rd year

Network Management Systems - Research

Brief Overview• What is Corba?• Emergence of the Corba based management• Corba as management technology.• JIDM Standard approach for corba based management: GDMO/ASN.1 to IDL translation Corba/TMN gateway architecture Structure of Corba based network management technology• Research1: architecture of corba based management and

performance of corba .

• Benefits & problems of using Corba based management technology

• Improving Performance of CORBA

• Research2: Approach to improve the performance of Corba based management and find out the sources of the performance overhead in corba.

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What is CORBA ?

• A standard defined by the Object Management Group (OMG)

• It enables communication of software components written in multiple computer languages and running on multiple computers.

Common Object Request Broker Architecture (CORBA)

Object Management Group (OMG)

• Object Management Group (OMG) is an international, open membership, non-profit computer industry standards consortium.

• Standardizes distributed object-oriented systems.

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Emergence of CORBA-based management

• Object-oriented framework for developing distributed systems.

• Satisfies concepts of ODP – Object Distributed Processing.

• Enhances the portability of applications that are developed across multiple network management platforms.

• Uses ORB for the interaction of the different objects over the network.

• ORB facilitates interoperability for communication among different object systems from different vendors.

ORB – object Request Broker - a middleware piece of software that allows to make program calls from one computer to another via network.

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CORBA as a Management Technology

• Fully object-oriented approach for management information modeling.

• Protocol – IIOP - Internet Inter ORB Protocol

• Integration of TMN and CORBA

• Managed objects are discovered by management applications using “Naming Service” provided by CORBA.

• Notification service – event driven management

• Client-server based organization model.

• Interfaces between managed object and manager – specified by IDL (Interface definition language)

• Several approaches – OMG, NMF, X/Open, ISO/OSI, ITU-T etc.

• Most Important approach : JIDM Joint Inter-Domain Management

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JIDM – Joint Inter Domain Management

• Reuse of OSI-SM infrastructure for management

• approach to accommodate existing networks and traditional management devices.

• Including generic gateway between different management technologies.

• Translation of GDMO/ASN.1 to CORBA IDL is needed to implement the Gateway.

• CMIP/SNMP PDU CORBA IDL

• In OSI architecture, MO description GDMO Data definition ASN.1

• In Corba, Description of distributed objects IDL

conversion

Reverse conversion

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JIDM Scenarios

Corba Manager

Gateway

CMIP/SNMP Agent

OSI Manager Gateway

Corba Manager Corba Agent

Corba Manager Corba Agent

Gateway

Gateway

IIOP

CMIP

IIOP

IIOPCMIPIIOP

CMIP/SNMP

Corba AgentIIOP

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Corba Agent• Corba Agent has CORBA server and IDL interfaces for each

GDMO.

• MO’s are not structured in MIB , visible at the same level.

• Each NE has its own ORB to interact with other Management entities.

• IDL interface of each MO defines attributes of MO and the operations supported.

• Interfaces are registered in the ORB Repository.

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Corba based Manager

• Supports distributed deployment of the components.

• Uses OMG defined interfaces to interact with the corba based agent

• The JIDM works can be divided into two main parts: Specification Translation and Interaction Translation.

• Specification Translation describes translation algorithm between CORBA IDL and GDMO/ASN.1

• Interaction translation describes the dynamic converting mechanisms between the protocols in one domain and the protocols within another domain.

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Corba based NM environment

GUI Client Application

Management Application

MO

ORB

MOORB

Embedded agent

MOORB

IIOP

IIOP

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Corba/TMN Gateway Architecture• In OSI, management architecture, CMIS provide services for management operations (such as create, delete, get, set, action and event notification).

CMIP transmission procedure of management information and the syntax of CMIS management services.

• In CORBA, the object implementation component defines operations that implement a CORBA IDL interface.

• When CORBA integrated into OSI management architecture then CORBA/CMIP gateway is needed for interaction of two inter-domain communication protocols and management operations.

• The gateway has OSI protocol stack for communicating with OSI-based TMN agent, and JIDM and OSI management gateway for supporting protocol conversion between CORBA and CMIP. These can support all processing of CMIS primitives.

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Design and Implementation of CORBA based Network Management Applications within TMN Framework from kyunpook national university(Ref [1] )

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Structure of Corba based Network Management Application

• CORBA-based network management application performs general MO operations and management operations associated with SMFAs.

• First, management application establishes connections with gateway for MO using several CORBA common services, such as naming, lifecycle and trader services.

• It performs CMIS operations using JIDM and OSI management gateway APIs provided by CORBA/CMIP gateway and MO Interface APIs provided by GDMO/ASN.1 to CORBA IDL translator.

• Using such MO operations and user-defined operations, SMFs may be composed and perform the management functions of functional areas.

• Management application provides user interface for supporting requests and responses of management behaviors.

• Upper layer management interface provides additional functionality which is necessary to the realization of TMN service management layer.

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Design and Implementation of CORBA based Network Management Applications within TMN Framework from kyunpook national university(Ref [2] )

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Design and Implementation of CORBA based Network Management Applications within TMN Framework from kyunpook national university(Ref [2] )

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• Design and Implementation of CORBA based Network Management Applications within TMN Framework By Kyungpook National university(Ref[1])

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Analysis

• Comparison of figure A with figure B :

• The elapsed time difference of the operation execution on CORBA-based NMS with the other is lager than in figure B.

• Single operation execution time is shorter than scoped operation execution time.

• In addition to this, execution time on CORBA-based NMS is slower than the others.

• Hence a lot of overhead in Corba. Some overhead in time for the connection of CORBA-based management application with CORBA/CMIP gateway.

• Therefore it may be necessary to find out the methods to minimize the connection time for system performance improvement.

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Problems with corba based Management technology

• Not scalable and fault tolerant, if the standard approach is used.

• Scalability is the main issue.

• It is not possible to handle so many objects efficiently using CORBA.• The scalability of the system is almost impossible to achieve,

because the run time requirements for the SNMP gateway servers and the naming service will grow linearly, when the number of managed SNMP agents grows.

• For Network management systems technology has to support bulk information retrieval. But Corba does not support it.

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Improving performance

• caching mechanism - fast and efficient access to the values of attributes of a managed object in corba management application .

• The caching mechanism enables CORBA Managed Object to maintain a local store of attribute values.

• Thus eliminating the need to contact the real underlying managed object when this information is requested.

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Further Research to improve performance

Research paper : Improving the Performance of Distributed CORBA Applications : Proceedings of the International Parallel and Distributed Processing Symposium (IPDPS.02) 1530-2075/02 - 2002 IEEE (Ref [2])

• This paper introduces new technique called “CORBA as needed” to improve the performance of distributed CORBA applications.

• First checks whether the interoperability functionality of CORBA communication methods are indeed needed or not in a particular invocation.

• If not needed for that invocation, then basically bypasses corba.

• Three design techniques :1. service approach2. Integration approach3. wrapper approach

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Designs of alternative approaches

• Bypass service : uses a similar interface as in CORBA, but uses TCP or UDP for communication.

Service approach Integration approach Wrapper approach

Services Bypass service

ORB

GIOP

TCP

IIOP

Services

ORB + Bypass service

GIOP

Wrapper

ORB

Services

GIOP

IIOP

TCP

IIOP

TCP

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Best approach : wrapper

• Best approach is : wrapper approach

Problems with other approaches :• Integration approach : 1. functionality of ORB are overloaded2. Loss of portability & interoperability3. Applications ORB dependent

• Service approach :1. Not clear how ORB interface with bypass service2. Performance overhead

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Further Research to improve performance

• Wrapper approach :• A separate module “wrapper” determining the platform compatibility &

establishing connection .

• Wrapper : interposed between client/server & ORB.• Client Initiates a connection with a server.

• The wrapper intercepts this invocation.

• invokes appropriate ORB methods to determine the server location and server platform.

• If server platform compatible with the client platform, the wrapper uses TCP or UDP to facilitate all the following method invocations

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Wrapper approach(Ref[2])

Client Server

Client-side wrapper Server-side wrapper

corba corba

Server locator

Determine server platform

Alternate connection

ORB(Logical channel)

TCP/UDP(Logical channel)

Network

compatible

incompatible

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Experiment evaluating performance

• Custom middleware(CM) is used for wrapper implementation

• Corba middleware : ORB : Visi-Broker

• Implementation of both is similar. Both provides location transparency.

• Difference : Corba - heterogeneous distributed platform CM - homogeneous distributed platform

• Experiment done for three string lengths : 100B,500B,10KB

• Over Three different networks : LAN, cross subnet, WAN

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Table : Application Performance (msec) (Ref[2])

Network Message size CM(wrapper approach) Corba (ORB : visi broker)

LAN 100B500B10K

86.393.3 187.0

140.6177.3260.0

Cross Subnet 100B500B10K

177.0 196.6433.6

220.3247.0921.3

WAN 100B500B10K

6042.3 6280.0 6685.3

6371.36443.67056.6

• CM outperforms the application implementation in Visibroker by 38% over LAN, 31% over cross subnet, and 5% over WAN.

• Reason for performance improvement: Data mapping, byte stuffing, and other interoperability functions to address the interoperability issue needed by the Visibroker.

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Sources of performance overhead

• To find out the sources of performance overhead , Installed a network sniffer on the network to examine packets sent by visibroker.

• Three important interoperability issues:1. variable byte ordering - no extra overhead2. byte alignment of primitive types - no significant overhead3. complete OMG IDL mapping to language data types - significant source of overhead

• IDL mapping : The parameter marshalling/unmarshalling . (encoding/decoding of parameters & putting it onto the network)

• During a remote invocation, the string parameter is marshalled from the language string type to the IDL string type .

• Similarly, on receiving the result, the IDL String type is unmarshalled to the language data type.

• Similar parameter marshalling / unmarshalling takes place on the server side.

• They did the experiment for several IDL – language data types . They found that this overhead is incurred for all the types.

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Conclusion

• Corba facilitates interoperability over distributed network, but it incurs performance overhead that can be reduced by using “corba as needed:wrapper approach” by research paper[2].

• The main source of performance overhead due to interoperability functionality in CORBA is parameter marshalling and unmarshalling needed in remote method invocation.

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References[1] Design and Implementation of CORBA based Network Management Applications within TMN Framework – By Moon- Sang Jeong , Jeong-Hwan Kim, Joon-Hyub Kwon and Jong-Tae Park - School of Electronic and Electrical Engineering , Kyungpook National University

[2] Improving the Performance of Distributed CORBA Applications : Proceedings of the International Parallel and Distributed Processing Symposium (IPDPS.02) 1530-2075/02 - 2002 IEEE [3] Network Management : Principles & Practices(2nd addition) by Mani subrimanian.