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rfc:rfc3052

Network Working Group M. Eder Request for Comments: 3052 Nokia Category: Informational S. Nag

                                                          January 2001
        Service Management Architectures Issues and Review

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 Many of the support functions necessary to exploit the mechanisms by
 which differing levels of service can be provided are limited in
 scope and a complete framework is non-existent.  Various efforts at
 such a framework have received a great deal of attention and
 represent a historical shift in scope for many of the organizations
 looking to address this problem.  The purpose of this document is to
 explore the problems of defining a Service management framework and
 to examine some of the issues that still need to be resolved.

1. Introduction

 Efforts to provide mechanisms to distinguish the priority given to
 one set of packets, or flows, relative to another are well underway
 and in many modern IP networks, best effort service will be just one
 of the many services being offered by the network as opposed to it
 being the only service provided.  Unfortunately, many of the support
 functions necessary to exploit the mechanisms by which network level
 service can be provided are limited in scope and a complete framework
 is non-existent.  Compounding the problem is the varied understanding
 of exactly what the scope of "service" is in an IP network.  IP, in
 contrast to connection oriented network technologies, will not be
 able to limit the definition of service management simply to end to
 end connectivity, but will combine service management with regards to
 transport with the service requirements of the actual applications
 and how they are using the network.  The phenomenal growth in data
 networks as well as the growth in application bandwidth usage has had
 the consequence that the existing methods of management are not
 sufficient to handle the growing demands of scale and complexity.

Eder & Nag Informational [Page 1] RFC 3052 Service Management Architectures January 2001

 The network and service management issue is going to be a major
 problem facing the networks of the future.  This realization is a
 significant motivating factor in various efforts within the IP
 community which has been traditionally reluctant to take on issues of
 this type [1].  The purpose of this document is to explore the
 problems of developing a framework for managing the network and
 services and to examine some of the issues that recent efforts have
 uncovered.

2. The Problem of Management Standards

 Network and service level issues traditionally are handled in IP
 networks by engineering the network to provide the best service
 possible for a single class of service.  Increasingly there is a
 desire that IP networks be used to carry data with specific QoS
 constraints.  IP networks will require a tremendous amount of
 management information to provision, maintain, validate, and bill for
 these new services.  The control and distribution of management
 information in complex communications networks is one of the most
 sophisticated tasks a network management framework must resolve. This
 is compounded by the likelihood that devices in IP networks will be
 varied and have differing management capabilities, ranging from
 complex computing and switching platforms to personal hand held
 devices and everything in between.  Scaling and performance
 requirements will make the task of defining a single management
 framework for these networks extremely complex.
 In the past standardization efforts have suggested a simplified model
 for management on the hypothesis that it can be extrapolated to solve
 complex systems.  This premise has often proved to be without merit
 because of the difficulty of developing such a model that meets both
 the operators heterogeneous, multi-vendor need and network equipment
 vendors specific needs.  At the center of efforts to devise a
 standard management model are attempts to develop an architecture or
 framework to control the management information. The same conflicting
 operator vs. vendor forces are present in the effort to establish a
 common framework architecture as are in the efforts to develop a
 common information model.
 Network operators requirements call for a framework that will permit
 centralized management of the network and require the minimal
 resources to operate and maintain while still providing tremendous
 flexibility in choice of equipment and creativity of defining
 services [2].  Operators may be less able to support change in their
 Operational Support Systems (OSS) then they are in the network
 infrastructure because the OSS is tightly integrated into the

Eder & Nag Informational [Page 2] RFC 3052 Service Management Architectures January 2001

 organizations business practices.  The need for flexibility, and the
 other desires identified above, operators expect to have meet by
 having equipment vendors support open and common interfaces.
 Device manufactures have a need for management that will best
 represent the features and capabilities of the equipment they are
 developing and any management solution that hinders the ability of
 the equipment vendors to efficiently bring innovation to the market
 is contrary to their objectives.
 The common framework for solving the management needs of operators
 and equipment vendors has been based on a centralized approach with a
 the manager agent architecture.  While providing a very
 straightforward approach to the problem of information management,
 this approach, and its variations, has not proved to scale well or
 allowed the flexibility required in today's modern data networks.
 Scaling and flexibility are especially a problem where there are many
 sophisticated network devices present.  Methods of control must be
 found that work and scale at the same speeds as that of the control
 plane of the network itself if a major concern of the management
 system is with the dynamic control of traffic in a network.
 Increasingly it is a requirement that customers at the edge of the
 network be able to have access to management functionality.  A
 centralized management approach may not provide the most convenient
 architecture to allow this capability.
 Frameworks based on a decentralized approach to the management
 architecture have gained momentum in recent years, but must address
 the possibility of having redundant management information throughout
 the network.  A decentralized framework may have advantages with
 regards to scaling and speed of operation, but information and state
 management becomes complex in this approach, resulting in additional
 complication in developing such systems.
 The complexity of managing a network increases dramatically as the
 number of services and the number and complexity of devices in the
 network increases.  The success of IP networks can be partially
 traced to the successful separation of transport control mechanisms
 from the complexity of service management, including billing.  As the
 trend in IP is to allow for classes of traffic that will have both
 transport and service dependencies it has become apparent that many
 of the management problems are becoming more complex in nature and
 are starting to resemble those of the traditional telecom provisioned
 service environment.  In the telecom environment no such separation
 exists between transport control mechanisms and service.  The Telecom
 community has struggled for years to come up with a standard solution
 for the problem in national and international standardization bodies
 and achieved a debatable amount of industry acceptance.

Eder & Nag Informational [Page 3] RFC 3052 Service Management Architectures January 2001

 Unfortunately, the hard learned lessons of how to manage the
 interdependencies between service and transport will be of
 questionable use to the IP community because of the much more limited
 concept of service in the telecommunications environment.
 Rules based management has received much attention as a method to
 reduce much of the overhead and operator intervention that was
 necessary in traditional management systems.  The potential exists
 that a rules-based system could reduce the rate at which management
 information is increasing, but given the tremendous growth in this
 information, the problems with the control of that information will
 continue to exist.  Rules add additional issues to the complexity of
 managing a network and as such will contribute to the information
 control problem.

2.1. IP QoS Management

 Much of the current management efforts are focused on solving control
 issues for IP QoS [3].  A number of open questions exist with the IP
 QoS architecture which will make it difficult to define a management
 architecture until they are resolved.  These are well documented in
 "Next steps for the IP QoS architecture" [4], but from the management
 perspective warrant emphasizing.
 Current IP QoS architectures have not defined if the service will be
 per-application or only a transport-layer option.  This will have
 significant impact both from a control perspective and from a billing
 and service assurance one.
 The assumption is that the routing best effort path will be used for
 both best effort traffic and for traffic of a different service
 level.  In addition to those issues raised in [4], best effort path
 routing may not be able to identify the parameters necessary to
 identify routes capable of sustaining distinguished service traffic.
 In any architecture where a premium service will be offered it is a
 strong requirement that the service be measurable and sustainable.
 Provisioning that service will require a coherent view of the network
 and not just the device management view that is currently implemented
 in most networks.

2.2. Promise of rules-based Management

 Management standardization efforts in the IP community have so far
 been concerned primarily with what is commonly referred to as
 "element management" or "device management" [5].  Generally there is
 agreement as to the scope of element management.  Once outside that
 domain efforts to divide that task along clear boundaries have proved

Eder & Nag Informational [Page 4] RFC 3052 Service Management Architectures January 2001

 elusive with many of the terms being used having their roots in the
 telecommunications industry and as such being of potentially limited
 use for IP management [1].  Confusion resulting from the ambiguity
 associated with what functions compose management beyond those
 intended for the element, is compounded by the broad scope for which
 network and service management standards apply.  Terms such a
 business goals, service management, and application management are
 not sufficiently defined to insure there will not be disagreement as
 to the actual scope of the management functions needed and to what
 extent interrelationships will exists between them.
 It is within this hazy domain that much of the recent efforts in
 rules-based management have been proposed as a potential solution.
 Efforts to devise a framework for policy management is an example of
 one of the most popular recent activities.  Proposed requirements for
 policy management look very much like pre-existing network management
 requirements [2], but specific models needed to define policy itself
 and related to the definition of policy to control DiffServ and RSVP
 based QoS are under development.

2.3. Service Management Requirements

 Efforts to define the requirements for a service management system
 are hindered by the different needs of network operators.  In an
 industry where much has been written about the trend towards
 convergence there still exist fundamental differences in the business
 needs of operators.

2.3.1. Enterprise

 The management requirements from both the operations and the network
 perspective have some interesting characteristics in the enterprise
 environment when compared to the public network.  In the enterprise
 end to end traffic management is implemented without the burden of
 complex tariff issues.  Service Level Agreements, while increasing in
 the enterprise, do not have the same operations impact as in the
 public network.  The high costs associated with implementing non-
 reputable auditing systems are usually not present.  This results in
 a substantial reduction in the number of expressions necessary to
 represent a particular networks business model.
 In the world of best effort service, rules-based management presents
 the possibility to give the IT department a tool the make the network
 appear to not be overloaded by prioritizing traffic.  This is done by
 prioritizing delay sensitive traffic (Web browsing) from traffic that
 is not delay sensitive (Email) or by prioritizing the traffic from a
 particular location or source.  This will, depending on the composite
 of an enterprises traffic, increase the useful life of the network

Eder & Nag Informational [Page 5] RFC 3052 Service Management Architectures January 2001

 without adding additional capacity.  This does not come without
 tradeoffs.  Both the purchase and management costs associated with
 the system must be calculated as well as the cost of the added
 complexity of adding additional control information to the network.

2.3.2. Service Provider

 It has for a long time been a goal of service providers to have a
 centralized management system.  While the motivation for this is very
 straightforward there exist some fundamental obstacles in achieving
 this goal.  Service providers often do not want to be tied to a
 single vendor and certainly do not want to be limited to only one
 model of any single vendors equipment.  At the same time bottom line
 costs are of paramount importance which often result in networks not
 being as heterogeneous as operators would like. Centralized
 management implies a scalable system able to manage potentially many
 heterogeneous pieces of equipment.  The amount of data necessary to
 achieve this is contrary to the scalability requirement.  In response
 to this problem it has been attempted many times to identify the
 common model that represents the subset common to all devices.
 Unfortunately all too often this set is either too complex,
 increasing the cost of devices, or too limited to preclude large
 amounts of device specific data thus defeating the purpose. For such
 a management model to be successful at the service level, the
 services being modeled must be standardized.  This is counter
 intuitive to the competitive model of which the service provider
 operates.  To be successful speed to market has become a key element
 that differentiates one service provider from another.  Constraints
 placed on equipment manufacturers and the management infrastructure
 by a centralized management system are also detrimental to this goal.
 While for a limited set of well defined services a central management
 approach is feasible, such a system can very quickly become a major
 contributor to the very problems it was intended to solve.

3. Network and Service Management

 Currently many of the efforts to define a framework for management
 are described in very implementation independent terms.  In actual
 fact the implementation of that framework directly affects for what
 situations the management system will be most beneficial.  While many
 past attempts to define a common management framework have failed it
 may be in the area of service management that such efforts finally
 gain industry acceptance.  It may be in the domain of service
 management that information models can be defined that are
 sufficiently specific to be useful and at that same time not have a
 negative impact on the equipment or service providers business needs.

Eder & Nag Informational [Page 6] RFC 3052 Service Management Architectures January 2001

 This section will discuss some of the issues that need to be resolved
 with regards to a service management framework to meet the
 requirements of the modern IP network.
 Some of the key concerns looking at a management system architecture
 include:
  1. The management interface and models supported
  2. The management system architecture
  3. Where and how functionality is realized

3.1. Architecture for information management

 Networks will consist of network elements that have existed prior to
 efforts to define a standard information model, rules-based or
 otherwise, and elements deployed after.  This problem has been
 addressed by some of the recent efforts in policy management.  Those
 elements that take into account policy are termed policy aware while
 those that do not are termed policy unaware.  The distinction being
 made that aware devices can interpret the policy information model or
 schema.  These issues apply equally to other standard management
 information.  In reality it is unlikely that any device will be fully
 policy aware for long, as the policy information model evolves, early
 devices will be only policy aware for those aspects of the model that
 had been defined at the time.  Key to success of any management
 framework is ability to handle revision and evolution.  A number
 methods exists provide this functionality.  One is designing the
 information models so that it can be extended but still be
 practically used in their original form.  A second is to provide an
 adaptation or proxy layer.  Each has advantages and disadvantages.
 Methods that attempt to extend the original model often overly
 constrain themselves.  Where the existing model cannot be extended
 new branches must be formed in the model that contain core management
 functionality.
 Adaptation methods can create performance and scalability problems
 and add complexity to the network by creating additional network
 elements.  A similar situation exists if the management framework is
 so flexible as to allow network elements to store locally information
 or choose to have information stored remotely.  From a device
 perspective, the criteria will be if the device can afford the logic
 based on other requirements it is designed to meet, and if the
 information can be retrieved in such a way as to support the
 performance and scalability requirements that are the subject of the
 information.  A dichotomy exists where there will be information that
 for reasons of performance and scalability will be transferred
 directly to the network elements in some situations, and in other

Eder & Nag Informational [Page 7] RFC 3052 Service Management Architectures January 2001

 situations, will exist in the management plan.  IP management efforts
 have left the level of detail needed to define the actual location of
 the management information to the implementation.  In a service
 management framework it may be necessary to achieve the desired
 results to supply a more complete framework along the lines of detail
 provided by the ITU-T telecommunications management network efforts
 where the interfaces and functionality across interfaces has been
 clearly defined.
 Information will need to exist in multiple locations simultaneously
 in any network architecture.  As the quantity and complexity of that
 information increases limitations quickly develop.  Changes in the
 information may need to be propagated in close to real time, further
 adding to the complication.

3.1.1. Rules-based Management

 A network management framework can be viewed as being divided into
 two essential functions.  The first deals with the aspects of
 managing the management information while the second deals with the
 aspects of transferring that management information into the network.
 The fundamental difference between rules based management and
 existing network management standards is that the management
 information is expressed as rules that reflect a desired level of
 service from the network as opposed to device specific management
 information.  Many of the information management requirements of
 traditional management systems still apply in a rules-based
 environment.  The network is composed of specific devices and it is
 at the point where rules are conveyed as device specific management
 information that this form of management will encounter some of its
 greatest challenges.  A necessary component of a solution to this
 problem will be a generic information model to which rules can be
 applied and a framework architecture for distributing rules
 throughout the network.  The task of finding the proper generic model
 that is not too great a burden to implement and yet provides a level
 of detail sufficient to manage a network has proved to be
 historically extremely difficult.  In many ways the degree to which
 rules based management will be able to solve management problems is
 dependent on the success of efforts to define a generic model and
 have it be widely implemented [1].
 One concept often discussed along with policy deals with the
 integration of legacy devices into the policy framework.  The
 presumption is that legacy devices would be able to participate in
 the policy decision by having policy information translated into the
 native management interface.  For this to succeed a device would have
 to support a functionality for which policy would be specified. This
 would limit the usefulness of this approach to only information

Eder & Nag Informational [Page 8] RFC 3052 Service Management Architectures January 2001

 logically abstracted to the native interface of the device.  Given
 that existing standard management interfaces do not support such
 functionality, all such devices would need to have a proprietary
 interface implemented.  The interface being based on the existing
 interface supported by the device would potentially not have the
 scaling capabilities needed for a policy management system.  Unlike a
 standard network management interface, were management information
 can be distributed between the adaptation layer and the network
 element, rules based management information may not be so easily
 distributed.
 The framework for integrating rules based management system with
 existing network devices is not readily apparent and further study is
 needed.  The problem exists further when one considers that there
 will be early policy aware devices that may not be aware as the
 policy models are extended.  The partially policy aware devices may
 represent additional architectural issues as it may not be possible
 to expect consistency in what aspects of policy a given devices
 implements if there does not exist formal sets of mandatory
 functionality with clear evolution paths.  It is paramount if the
 policy management framework is going to able to evolve to accommodate
 the ever-increasing number of services likely to be supported by IP
 networks of the future that an evolution path be built into the
 framework.

3.2. Policy Protocol

 The need for a policy protocol is important in the context of a
 policy aware element that is performing a certain 'service'.  It is
 important to note here that not all elements will be aware of all
 service policies related to every service at all times.  Therefore it
 makes sense for an element to be aware of a certain service policy if
 that element is required for a given service at any instant in time.
 With the dynamics of a network where elements and links go up and
 down, a notion of a 'policy protocol' may become necessary.  The idea
 of a 'policy protocol' that runs in a multi-service network requiring
 multi-service policies.  For example; consider two arbitrary end
 nodes having multiple routing paths between them. Let's then assume
 that a certain path carries a certain service based on some Intserv
 bandwidth reservation technique.  Let's also then deduce that the
 elements along that path have some element specific policy statements
 that have been configured on them to support that requirement.  If
 now at any given instance any link or any element were to be
 unavailable along that path, the 'policy protocol' should be
 initiated to automatically go and configure the same service-policies

Eder & Nag Informational [Page 9] RFC 3052 Service Management Architectures January 2001

 on the elements along another routed path connecting the very same
 end points, so that there is no disruption in service and so that no
 human/operator intervention is required.
 The association of policy with the policy target is an area where
 considerable study may need to be done.  Some issues are if this
 needs to be explicitly done or if the policy can be so written that a
 common description of the target is also included?  Allowing a policy
 target to retrieve those policies that are relevant to it.

4. Conclusions

 Understanding the set of problems facing IP network management in
 general will be key in defining a comprehensive framework
 architecture that meets the needs of operators.  Additional risks are
 created by applying new management techniques to the management of IP
 networks.  The consequence of implementing management operations
 based on architectures that may not be compatible with existing
 management systems will still need to be explored.
 Given that many network devices in IP networks are making routing
 decisions based on information received via routing protocols it
 seems sensible that they also make QoS decisions in a similar
 fashion.
 Historically the broader the scope of a network management
 standardization effort the less likely it has been to succeed.
 Management standardization efforts must be careful to have clearly
 defined goals and requirements less they to experience the same fate
 as previous such efforts.
 As IP continues to extend it's concept of service beyond that of best
 effort to include, among other things, differentiate treatment of
 packets, it will become increasingly necessary to have mechanisms
 capable of supporting these extensions.  Efforts to define a common
 management model and framework have proven to be historically
 elusive.  Information models, whether they be traditional or rules-
 based, must address these past problems.  The desire to keep a
 competitive advantage, and the reality that a common model, to be
 truly common, will not provide sufficient detail to fully manage a
 device, has often slowed the acceptance on the part of equipment
 vendors to this approach.
 As IP continues to extend it's concept of service beyond that of best
 effort to include, among other things, differentiate treatment of
 packets it will become increasingly necessary to have mechanisms
 capable of supporting these extensions.

Eder & Nag Informational [Page 10] RFC 3052 Service Management Architectures January 2001

5. Security Considerations

 The exchange of management information in a network is one of the
 most sensitive from a security perspective.  Management protocols
 must address security to insure the integrity of the data.  A
 management architecture must provide for security considerations from
 its inception to insure the authenticity of the information provider
 and that the security mechanisms not be so cumbersome as to make them
 not feasible to implement.

6. Reference

 [1] Michael Eder, Sid Nag, Raj Bansal, "IP Service Management
     Framework", Work in Progress, October 1999.
 [2] Hugh Mahon, Yoram Bernet, and Shai Herzog, "Requirements for a
     Policy Management System", Work in Progress.
 [3] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for
     Policy-based Admission Control", RFC 2753, January 2000.
 [4] Huston, G., "Next Steps for the IP QoS Architecture", RFC 2990,
     November 2000.
 [5] McCloghrie, K. and M. Rose, "Management Information Base for
     Network Management of TCP/IP-based internets" RFC 1156, May 1990.

7. Authors' Addresses

 Michael Eder
 Nokia
 5 Wayside Road
 Burlington, MA  01803
 EMail: michael.eder@nokia.com
 Sid Nag
 PO Box 104
 Holmdel, NJ 07733
 EMail: thinker@monmouth.com

Eder & Nag Informational [Page 11] RFC 3052 Service Management Architectures January 2001

8. Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Eder & Nag Informational [Page 12]

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