NSIS Working Group
   Internet Draft                                   M. Brunner (Editor)
   Document: draft-ietf-nsis-req-02.txt                             NEC
   Expires:  November 2002                                     May 2002


                 Requirements for QoS Signaling Protocols
                      <draft-ietf-nsis-req-02.txt>

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               Requirements for QoS Signaling Protocols       May 2002

Abstract

   This document defines requirements for signaling QoS across
   different network environments. To achieve wide applicability of the
   requirements, the starting point is a diverse set of scenarios/use
   cases concerning various types of networks and application
   interactions.  We also provide an outline structure for the problem,
   including QoS related terminology. Taken with the scenarios, this
   allows us to focus more precisely on which parts of the overall QoS
   problem needs to be solved. We present the assumptions and the
   aspects not considered within scope before listing the requirements
   grouped according to areas such as architecture and design goals,
   signaling flows, layering, performance, flexibility, security, and
   mobility.

1  Introduction

   This document defines requirements for signaling QoS across
   different network environments. It does not list any problems of
   existing QoS signaling protocols such as RSVP.

   In order to derive requirements for QoS signaling it is necessary to
   first have a clear idea of the scope within which they are
   applicable.
   We describe a set of QoS signaling scenarios and use cases in the
   Appendix of that document. These scenarios derive from a variety of
   backgrounds, and help obtain a clearer picture of what is in or out
   of scope of the NSIS work. They illustrate the problem of QoS
   signaling from various perspectives (end-system, access network,
   core network) and for various areas (fixed line, mobile, wireless
   environments). As the NSIS work becomes more clearly defined,
   scenarios will be added or dropped, or defined in more detail.

   Based on these scenarios, we are able to define the QoS signaling
   problem on a more abstract level. In Section 3, we thus present a
   simple conceptual model of the QoS signaling problem, describe the
   entities involved in QoS signaling, and typical signaling paths. In
   Section 4 we list assumptions and exclusions.

   The model of Section 3 allows deriving requirements from the
   scenarios presented in the appendix in a coherent and consistent
   manner. Requirements are grouped according to areas such as
   Architecture and design goals, Signaling Flows, Layering,
   Performance, Flexibility, Security and Mobility.

   QoS is a pretty large field with a lot of interaction with other
   protocols, mechanisms, applications etc. In the following, some
   thoughts from an end-system point of view and from a network point
   of view.

   End-system perspective: In future mobile terminals, the support of
   adaptive applications is more and more important. Adaptively can be
   seen as an important technique to react to QoS violations that may
   occur frequently, e.g.,  in wireless environments due to changed

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   environmental and network conditions. This may result in degraded
   end-to-end performance. It is then up to adaptive applications to
   react to the new resource availability. Therefore, it is essential
   to define interoperability between media-, mobility- and QoS
   management. While most likely mobile terminals cannot assume, that
   explicit QoS reservation schemes are available, some access networks
   nevertheless may offer such capabilities. Applications subscribed to
   an end-system QoS management system should be supported with a
   dedicated QoS API to set-up, control and adapt media sessions.

   Network perspective: QoS enabled IP networks are expected to handle
   two different kinds of QoS granularities: per-flow QoS and per-
   trunk/per-class QoS. Per-flow QoS might be needed in access networks
   and may there be subject of QoS signaling. However, in the core
   network only per-trunk or per-class QoS can be considered for
   scalability reasons. Therefore there might be different requirements
   on QoS signaling applying to different parts of the network. In the
   access network QoS signaling is an interaction between end systems
   and access routers or access network QoS managers (in the following
   we call them QoS initiator and QoS controller). In the core network
   QoS signaling refers to trunks or classes of traffic between core
   and edge systems or between peering core systems. Please note that
   this does not exclude the transport of per-flow signaling through
   core networks.

   It is clear from these descriptions that the subject of QoS is
   uniquely complex and any investigation could potentially have a very
   broad scope - so broad that it is a challenge to focus work on an
   area which could lead to a concrete and useful result. This is our
   motivation for considering a set of use cases, which map out the
   domain of application that we want to address. It is also the
   motivation for defining a problem structure, which allows us to
   state the boundaries of what types of functionality to consider, and
   to list background assumptions.

   There are several areas of the requirements related to networking
   aspects which are incomplete, for example, interaction with host and
   site multi-homing, use of anycast services, and so on. These issues
   should be considered in any future requirement analysis work.

2  Terminology

   In the area of Qualiaty of Service (QoS) it is quite difficult and
   an exercise for its own to define terminology. Nevertheless, we
   tried to list the most often used terms in the draft and tried to
   explain them. However, don't be to religious about it, they are not
   meant to prescribe any thing in the draft.

   Aggregate: a group of flows, usually with similar QoS requirements,
   which can be treated together as a whole with a single overall QoS
   requirement for signaling and provisioning. Aggregates and flows can
   be further aggregated together.



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   [QoS] Domain: a collection of networks under the same administrative
   control and grouped together for administrative purposes.

   Egress point: the router via which a path exits a domain/subdomain.

   End Host: the end system or host, for whose flows QoS is being
   requested and provisioned.

   End-to-End QoS: the QoS delivered by the network between two
   communicating end hosts.  End-to-end QoS co-ordinates and enforces
   predefined traffic management policies across multiple network
   entities and administrative domains.

   Edge-to-edge QoS: QoS within an administrative domain that connects
   to other networks rather than hosts or end systems.

   Flow: a traffic stream (sequence of IP packets between two end
   systems) for which a specific level of QoS is to be provided. The
   flow can be unicast (uni- or bi-directional) or multicast.

   Flow Administration: represents the policy associated with how flows
   should be treated in the network, for example whether and how the
   flows should be aggregated.  It may consist of both user and local
   network management information.

   Higher Layers: the higher layer (transport protocol and application)
   functions that request QoS from the network layer. The request might
   be a trigger generated within the end system, or the trigger might
   be provided by some entity within the network (e.g. application
   proxy or policy server).

   Indication: feedback from QoS provisioning to indicate the current
   QoS being provided to a flow or aggregate, and whether any
   violations have been detected by the QoS technology being used
   within the local domain/subdomain.

   Ingress point: the router via which a path enters a
   domain/subdomain.

   Mapping: the act of transforming parameters from QSCs to values that
   are meaningful to the actual QoS technology in use in the
   domain/subdomain.

   Path: the route across the networks taken by a flow or aggregate,
   i.e. which domains/subdomains it passes through and the
   egress/ingress points for each.

   Path segment: the segment of a path within a single
   domain/subdomain.

   QoS Administration Function: a generic term for all functions
   associated with admission control, policy control, traffic
   engineering etc.


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   QoS Control Information: the information the governs the QoS
   treatment to be applied to a flow or aggregate, including the QSC,
   flow administration, and any associated security or accounting
   information.

   QoS Controller: this is responsible for interpreting the signaling
   carrying the user QoS parameters, optionally inserting/modifying the
   parameters according to local network QoS management policy, and
   invoking local QoS provisioning mechanisms. Note that q QoS
   controller might have very different functionality depending on
   where in the network and in what environment they are implemented.

   QoS Initiator: this is responsible for generating the QSCs for
   traffic flow(s) based on user or application requirements and
   signaling them to the network as well as invoking local QoS
   provisioning mechanisms.  This can be located in the end system, but
   may reside elsewhere in network.

   QoS Provisioning: the act of actually allocating resources to a flow
   or aggregate of flows, may include mechanisms such as LSP initiation
   for MPLS, packet scheduler configuration within a router, and so on.
   The mechanisms depend on the overall QoS technology being used
   within the [sub]domain.

   QoS Service Classes (QSC): specify the QoS requirements of a traffic
   flow or aggregate.  Can be further sub-divided into user specific
   and network related parameters

   QoS Signaling: a way to communicate QSCs and QoS management
   information between hosts, end systems and network devices etc.  May
   include request and response messages to facilitate negotiation/re-
   negotiation, asynchronous feedback messages (not delivered upon
   request) to inform End Hosts, QoS initiators and QoS controllers
   about current QoS levels, and QoS querying facilities.

   [QoS] Subdomain: a network within an administrative domain using a
   uniform technology/QoS provisioning function to provision resources.

   QoS Technology: a generic term for a set of protocols, standards and
   mechanisms that can be used within a QoS domain/subdomain to manage
   the QoS provided to flows or aggregates that traverse the domain.
   Examples might include MPLS, DiffServ, and so on. A QoS technology
   is associated with certain QoS provisioning techniques.

   QoS Violation: occurs when the QoS applied to a flow or aggregate
   does not meet the requested and negotiated QoS agreed for it.

   Resource: something of value in a network infrastructure to which
   rules or policy criteria are first applied before access is granted.
   Examples of resources include the buffers in a router and bandwidth
   on an interface.




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   Resource Allocation: part of a resource that has been dedicated for
   the use of a particular traffic type for a period of time through
   the application of policies.

   Sender-initiated QoS signaling protocol: A sender-initiated QoS
   signaling protocol is a protocol (see e.g., YESSIR [8], RMD [10])
   where the QI initiates the signaling on behalf of the sender of the
   data. What this means is that admission control and resource
   allocation functions are processed from the data sender towards the
   data receiver. However, the triggering instance is not specified.

   Receiver-initiated QoS signalling protocol: A receiver-initiated
   protocol, (see e.g., RSVP [9]) is a protocol where the QoS
   reservations are initiated by the QoS Reiceiver on behalf of the
   receiver of the user data. What this means is that admission control
   and resource allocation functions are processed from the data
   receiver back towards the data sender. However, the triggering
   instance is not specified.

3  Problem Statement and Scope

   We provide in the following a preliminary architectural picture as a
   basis for discussion. We will refer to it in the following
   requirement section.

   A set of issues and problems to be solved has been given at a top
   level by the use cases/scenarios of the appendix. However, the
   problem of QoS has an extremely wide scope and there is a great deal
   of work already done to provide different components of the
   solution, such as QoS technologies for example. A basic goal should
   be to re-use these wherever possible, and to focus requirements work
   at an early stage on those areas where a new solution is needed
   (e.g. an especially simple one). We also try to avoid defining
   requirements related to internal implementation aspects.

   In this section, we present a simple conceptual model of the overall
   QoS problem in order to identify the applicability to NSIS of
   requirements derived from the use cases, and to clarify the scope of
   the work, including any open issues. This model also identifies
   further sources of requirements from external interactions with
   other parts of an overall QoS solution, clarifies the terminology
   used, and allows the statement of design goals about the nature of
   the solution (see section 5).

   Note that this model is intended not to constrain the technical
   approach taken subsequently, simply to allow concrete phrasing of
   requirements (e.g. requirements about placement of the QoS
   initiator, or ability to 'drive' particular QoS technologies.)

   Roughly, the scope of NSIS is assumed to be the interaction between
   the QoS initiator and QoS controller(s), including selection of
   signaling protocols to carry the QoS information, and the
   syntax/semantics of the information that is exchanged. Further


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   statements on assumptions/exclusions are given in the next Section.
   The main elements are:

   1. Something that starts the request for QoS, the QoS Initiator.

   This might be in the end system or within some other part of the
   network. The distinguishing feature of the QoS initiator is that it
   acts on triggers coming (directly or indirectly) from the higher
   layers in the end systems. It needs to map the QoS requested by
   them, and also provides feedback information to the higher layers
   which might be used by transport layer rate management or adaptive
   applications.

   2. Something that assists in managing QoS further along the path,
   the QoS controller.

   The QoS controller does not interact with higher layers, but
   interacts with the QoS initiator and possibly more QoS controllers
   on the path, edge to edge or possibly end to end.

   3. The QoS initiator and controller(s) interact with each other,
   path segment by path segment. This interaction involves the exchange
   of data (QoS control information) over some signaling protocol.

   4. The path segment traverses an underlying network (QoS domain or
   subdomain) covering one or more IP hops. The underlying network uses
   some local QoS technology. This QoS technology has to be provisioned
   appropriately for the flow, and this is done by the QoS initiator
   and controller(s), mapping their QoS control information to
   technology-related QoS parameters and receiving indications about
   success or failure in response.

   Now concentrating more on the overall end to end (multiple QoS
   domains) aspects, in particular:

   1. The QoS initiator need not be located at an end system, and the
   QoS controllers are not assumed to be located on the flow's data
   path. However, they must be able to identify the ingress and egress
   points for the flow path as it traverses the domain/subdomain. Any
   signaling protocol must be able to find the appropriate QoS
   controller and carry this ingress/egress point information.

   2. We see the network at the level of domains/subdomains rather than
   individual routers (except in the special case that the domain
   contains one link). Domains are assumed to be administrative
   entities, so security requirements apply to the signaling between
   them. Subdomains are introduced to allow the fact a given QoS
   provisioning mechanism may only be used within a part of a domain,
   typically for a particular subnetwork technology boundary.
   Aggregation can also take place at subdomain boundaries.

   3. Any domain may contain QoS administration functions (e.g. to do
   with traffic engineering, admission control, policy and so on).


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   These are assumed to interact with the QoS initiator and controllers
   (and end systems) using standard mechanisms.

   4. The placement of the QoS initiators and QoS controllers is not
   fixed. Actually, there are two extreme cases:

   - Each router on the data path implements a QoS controller and QoS
   initiator.

   - Only the end systems incorporate a QoS controller and QoS
   initiator, which means the end systems need to have QoS provisioning
   capabilities. However this case does not seam to be realistic but
   shows the flexible allocation of the controller and initiator
   function.

4  Assumptions and Exclusions

4.1 Assumptions and Non-Assumptions

   1. The NSIS signaling could run end to end, end to edge, or edge to
   edge, or network-to-network ((between providers), depending on what
   point in the network acts as the initiator, and how far towards the
   other end of the network the signaling propagates. Although the
   figures show QoS controllers at a very limited number of locations
   in the network (e.g. at domain or subdomain borders, or even
   controlling a complete domain), this is only one possible case. In
   general, we could expect QoS controllers to become more 'dense'
   towards the edges of the network, but this is not a requirement. An
   overprovisioned domain might contain no QoS controllers at all (and
   be NSIS transparent); at the other extreme, QoS controllers might be
   placed at every router. In the latter case, QoS provisioning can be
   carried out in a local implementation-dependent way without further
   signalling, whereas in the case of remote QoS controllers, a
   provisioning protocol might be needed to control the routers along
   the path. This provisioning protocol is then independent of the end
   to end NSIS signalling.

   2. We do not consider 'pure' end-to-end QoS signaling that is not
   interpreted anywhere within the network. Such signaling is an
   application-layer issue and IETF protocols such as SIP etc. can be
   used.

   3. Where the signaling does cover several QoS domains or subdomains,
   we do not exclude that different signaling protocols are used in
   each path segment. We only place requirements on the universality of
   the QoS control information that is being transported. (The goals
   here would be to allow the use of signaling protocols which are
   matched to the characteristics of the portion of the network being
   traversed.) Note that the outcome of NSIS work might result in
   various protocols or various flavors of the same protocol. This
   implies the need for the translation of information into QoS domain
   specific format as well.



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   4. We assume that the service definitions a QoS initiator can ask
   for are known in advance of the signaling protocol running. Service
   definition includes QoS parameters, life-time of QoS guarantee etc.
   There are many ways a service requester get to know about it. There
   might be standardized services, the definition can be negotiated
   together with a contract, the service definition is published at a
   Web-page, etc.

   5. We assume that there are means for the discovery of NSIS entities
   in order to know the signaling peers (solutions include static
   configuration, automatically discovered, or implicitly runs over the
   right nodes, etc.)

4.2 Exclusions

   1. Development of specific mechanisms and algorithms for application
   and transport layer adaptation are not considered, nor are the
   protocols that would support it.

   2. Specific mechanisms (APIs and so on) for interaction between
   transport/applications and the network layer are not considered,
   except to clarify the requirements on the negotiation capabilities
   and information semantics that would be needed of the signaling
   protocol. The same applies to application adaptation mechanisms.

   3. Specific mechanisms for QoS provisioning within a
   domain/subdomain are not considered. It should be possible to
   exploit these mechanisms optimally within the end to end context.
   Consideration of how to do this might generate new requirements for
   NSIS however. For example, the information needed by an QoS
   controller to manage a radio subnetwork needs to be provided by the
   NSIS solution.

   4. Specific mechanisms (APIs and so on) for interaction between the
   network layer and underlying QoS provisioning mechanisms are not
   considered.

   5. Interaction with QoS administration capabilities is not
   considered. Standard protocols should be used for this (e.g. COPS).
   This may imply requirements for the sort of information that should
   be exchanged between the NSIS network QoS entities.

   6. Security issues related to multicasting are outside the scope of
   the QoS signaling protocol.

   Since multicasting is currently not an issue for the QoS protocol,
   security issues related to multicast are outside the scope.
   Multicast security may additionally be an application issue that is
   also outside the scope of the QoS protocol.

   7. Protection of non-QoS signaling messages is outside the scope of
   the QoS protocol



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   Security protection of data messages transmitted along the
   established QoS path is outside the scope of the QoS protocol. These
   security properties are likely to be application specific and may be
   provided by the corresponding application layer protocol.

   8. Service definitions and QoS classes are out of scope. Together
   with the service definition any definition of service specific
   parameters are not considered in this draft. Only the base NSIS
   signaling protocol for transporting the QoS/service information are
   handled.

   9. Similarly, specific methods, protocols, and ways to express QoS
   information in the Application/Session level are not considered
   (e.g., SDP, SIP, RTSP, etc.).

   10. The specification of any extensions needed to signal QoS
   information via application level protocols (e.g. SDP(ng)), and the
   mapping on NSIS information are considered outside of the scope of
   NSIS working group, as this work is in the direct scope of other
   IETF working groups (e.g. MMUSIC).

5  Requirements

   This section defines more detailed requirements for a QoS signaling
   solution, derived from consideration of the use cases/scenarios, and
   respecting the framework, scoping assumptions, and terminology
   considered earlier. The requirements are in subsections, grouped
   roughly according to general technical aspects: architecture and
   design goals, topology issues, QoS parameters, performance,
   security, information, and flexibility.

   Two general (and potentially contradictory) goals for the solution
   are that it should be applicable in a very wide range of scenarios,
   and at the same time lightweight in implementation complexity and
   resource requirements in nodes. One approach to this is that the
   solution could deal with certain requirements via modular components
   or capabilities, which are optional to implement in individual
   nodes.

   Some of the requirements are technically contradictory. Depending on
   the scenarios a solution applies to, one or the other requirement is
   applicable.

   Find in Section 6 the MUSTs, SHOULDs, and MAYs

5.1 Architecture and Design Goals

   This section contains requirements related to desirable overall
   characteristics of a solution, e.g. enabling flexibility, or
   independence of parts of the framework.

5.1.1 Applicability for different QoS technologies.



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   The QoS signaling protocol must work with various QoS technologies.
   The information exchanged over the signaling protocol must be in
   such detail and quantity that it is useful for various QoS
   technologies.

5.1.2 Resource availability information on request

   In some scenarios, e.g., the mobile terminal scenario, it is
   required to query, whether resources are available, without
   performing a reservation on the resource. One solution might be a
   feedback mechanism based on which a QoS inferred handover can take
   place.

5.1.3 Modularity

   A modular design allows for more lightweight implementations, if
   fewer features are needed. Mutually exclusive solutions are
   supported. Examples for modularity:

   - Work over any kind of network (narrowband / broadband, error-prone
   / reliable...) - This implies low bandwidth signaling and redundant
   information must be supported if necessary.

   - In case QoS requirements are soft (e.g. banking transactions,
   gaming), fast and lightweight signaling (e.g., not more than one
   round-trip time)

   - Uni- and bi-directional reservations are possible

5.1.4 Decoupling of protocol and information it is carrying

   The signaling protocol(s) used must be clearly separated from the
   QoS control information being transported. This provides for the
   independent development of these two aspects of the solution, and
   allows for this control information to be carried within other
   protocols, including application layer ones, existing ones or those
   being developed in the future. The gained flexibility in the
   information transported allows for the applicability of the same
   protocol in various scenarios.
   However, note that the information carried needs to be the same.
   Otherwise interoperability is difficult to achieve.

5.1.5 Reuse of existing QoS provisioning

   Reuse existing QoS functions and protocols for QoS provisioning
   within a domain/subdomain unchanged. (Motivation: 'Don't re-invent
   the wheel'.)

5.1.6 Independence of signaling and provisioning paradigm

   The QoS signaling should be independent of the paradigm and
   mechanism of QoS provisioning. The independence allows for using the
   NSIS protocol together with various QoS technologies.


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               Requirements for QoS Signaling Protocols       May 2002

5.2 Signaling Flows

   This section contains requirements related to the possible signaling
   flows that should be supported, e.g. over what parts of the flow
   path, between what entities (end-systems, routers, middleboxes,
   management systems), in which direction.

5.2.1 Free placement of QoS Initiator and QoS Controllers functions

   The protocol(s) must work in various scenarios such as host-to-
   network-to-host, edge-to-edge, (e.g., just within one providers
   domain), user-to-network (from end system into the network, ending,
   e.g., at the entry to the network and vice versa), network-to-
   network (e.g., between providers).

   Placing the QoS controller and initiator functions at different
   locations allows for various scenarios to work with the same or
   similar protocols.

5.2.2 No constraint of the QoS signaling and QoS Controllers to be in
     the data path.

   There is a set of scenarios, where QoS signaling is not on the data
   path. The QoS Controller being in the data path is one extreme case
   and useful in certain cases.

   There are going to be cases where a centralized entity will take a
   decision about QoS requests. In this case, there's no question there
   is no need to have data follow the signalling path.

   There are going to be cases wiout a centralized entity managing
   resources and the signaling will be used as a tool for resource
   management. For various reasons (such as efficient use of expensive
   bandwidth), one will want to have fine-grained, fast, and very
   dynamic control of the resources in the network. -

   There are going to be cases where there will be neither signaling
   nor a centralized entity (overprovisioning). Nothing has to be done
   anyway.

   One can capture the requirement with the following wording: If one
   views the domain with a QoS technology as a virtual router then NSIS
   signaling used between those virtual routers must follow the same
   path as the data.

   Routing the signaling protocol along an independent path is desired
   by network operators/designers. Ideally, the capability to route the
   protocol along an independent path would give the network
   designer/operator the option to manage bandwidth utilization through
   the topology.

   There are other possibilities as well. An NSIS protocol must accept
   all of these possibilities.


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5.2.3 Concealment of topology and technology information

   The QoS protocol should allow hiding the internal structure of a QoS
   domain from end-nodes and from other networks. Hence an adversary
   should not be able to learn the internal structure of a network with
   the help of the QoS protocol.

   In various scenarios, topology information should be hidden for
   various reasons. From a business point of view, some administrations
   don't want to reveal the topology and technology used.

5.2.4 Optional transparency of QoS signaling to network

   It should be possible that the QoS signaling for some flows traverse
   path segments transparently, i.e., without interpretation at QoS
   controllers within the network. An example would be a subdomain
   within a core network, which only interpreted signaling for
   aggregates established at the domain edge, with the flow-related
   signaling passing transparently through it.

5.3 Additional information beyond signaling of QoS information

   This section contains the desired signaling (messages) for other
   purposes other than that for conveying QoS parameters.


5.3.1 Explicit release of resources

   When a QoS reservation is no longer necessary, e.g. because the
   application terminates, or because a mobile host experienced a hand-
   off, it must be possible to explicitly release resources.

5.3.2 Possibility for automatic release of resources after failure

   When the QoS Initiator goes down, the resources it requested in the
   network should be released, since they will no longer be necessary.

   After detection of a failure in the network, any QoS
   controller/initiator must be able to release a reservation it is
   involved in. For example, this may require signaling of the "Release
   after Failure" message upstream as well as downstream, or soft state
   timing out of reservations.

   Note that this might need to work together with a notification
   mechanism.


5.3.3 Possibility for automatic re-setup of resources after recovery

   In case of a failure, the reservation can get setup again
   automatically. It enables sort of a persistent reservation, if the
   QoS Initiator requests it. In scenarios where the reservations are



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               Requirements for QoS Signaling Protocols       May 2002

   on a longer time scale, this could make sense to reduce the
   signaling load in case of failure and recovery.

5.3.4 Prompt notification of QoS violation in case of error/failure to
     QoS Initiator and QoS Controllers

   QoS Controllers should be able to notify the QoS Initiator, if there
   is an error inside the network. There are two types of network
   errors:

   Recoverable errors: This type error can be locally repaired by the
   network nodes. The network nodes do not have to notify the users of
   the error immediately. This is a condition when the danger of
   degradation (or actual short term degradation) of the provided QoS
   was overcome by the network (QoS controller) itself.

   Unrecoverable errors: the network nodes cannot handle this type of
   error, and have to notify the users as soon as possible.


5.3.5 Feedback about success of request for QoS guarantees

   A request for QoS must be answered at least with yes or no. However,
   it might be useful in case of a negative answer to also get a
   description of what might be the QoS one can successfully request
   etc. So it might be useful to include an opaque element into the
   answer. The element heavily depends on the service requested.

5.3.6 Allow local QoS information exchange between nodes of the same
     administrative domain

   The QoS signaling protocol must be able to exchange local QoS
   information between QoS controllers located within one single
   domain. Local QoS information might, for example, be IP addresses,
   severe congestion notification, notification of successful or
   erroneous processing of QoS signaling messages.

   In some cases, the NSIS QoS signalling protocol may carry
   identification of the QoS controllers located at the boundaries of a
   domain. However, the identification of edge should not be visible to
   the end host (QoS initiator) and only applies within one QoS
   administrative domain.

5.4 Layering

   This section contains requirements related to the way the signaling
   being considered interacts with upper layer functions (users,
   applications, and QoS administration), and lower layer QoS
   technologies.

5.4.1 The signaling protocol and QoS control information should be
     application independent.



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               Requirements for QoS Signaling Protocols       May 2002

   However, opaque application information might get transported in the
   signaling message, without being handled in the network. Development
   and deployment of new applications should be possible without
   impacting the network infrastructure. Additionally, QoS protocols
   are expected to conform to the Internet principles.

5.5 QoS Control Information

   This section contains requirements related to the QoS control
   information that needs to be exchanged.

5.5.1 Mutability information on parameters

   It should be possible for the initiator to control the mutability of
   the QSC information. This prevents from being changed in a non-
   recoverable way. The initiator should be able to control what is
   requested end to end, without the request being gradually mutated as
   it passes through a sequence of domains. This implies that in case
   of changes made on the parameters, the original requested ones must
   still be available.

   Note that we do not require anything about particular QoS paramters
   being changed.

5.5.2 Possibility to add and remove local domain information

   It should be possible for the QoS control functions to add and
   remove local scope elements. E.g., at the entrance to a QoS domain
   domain-specific information is added, which is used in this domain
   only, and the information is removed again when a signaling message
   leaves the domain. The motivation is in the economy of re-use the
   protocol for domain internal signaling of various information. Where
   additional information is needed for QoS control within a particular
   domain, it should be possible to carry this at the same time as the
   'end to end' information.)

5.5.3 Independence of reservation identifier

   A reservation identifier must be used, which is independent of the
   flow identifier, the IP address of the QoS Initiator, and the flow
   end-points. Various scenarios in the mobility area require this
   independence because flows resulting from handoff might have changed
   end-points etc. but still have the same QoS requirement.

5.5.4 Seamless modification of already reserved QoS

   In many case, the reservation needs to be updated (up or downgrade).
   This must happen seamlessly without service interruption. At least
   the signaling protocol must allow for it, even if some data path
   elements might not be capable of doing so.

5.5.5 Signaling must support quantitative, qualitative, and relative
     QoS specifications


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               Requirements for QoS Signaling Protocols       May 2002

5.6 Performance

   This section discusses performance requirements and evaluation
   criteria and the way in which these could and should be traded off
   against each other in various parts of the solution.

   Scalability is a must anyway. However, depending on the scenario the
   question to which extends the protocol must be scalable.

5.6.1 Scalability in the number of messages received by a signaling
     communication partner (QoS initiator and controller)

5.6.2 Scalability in number of hand-offs

5.6.3 Scalability in the number of interactions for setting up a
     reservation

5.6.4 Scalability in the number of state per entity (QoS initiators and
     QoS controllers)

5.6.5 Scalability in CPU use (end terminal and intermediate nodes)

5.6.6 Low latency in setup

   Low latency is only needed in scenarios, where reservations are in a
   short time scale (e.g. handover in mobile environments), or where
   human interaction is immediately concerned (e.g., voice
   communication setup delay)

5.6.7 Allow for low bandwidth consumption for signaling protocol

   Again only small sets of scenarios call for low bandwidth, mainly
   those where wireless links are involved.

   Note that many of the performance issues are heavily dependent on
   the scenario assumed and are normally a trade-off between speed,
   reliability, complexity, and scalability. The trade-off varies in
   different parts of the network. For example, in radio access
   networks low bandwidth consumption will overweight the low latency
   requirement, while in core networks it may be reverse.

5.6.8 Ability to constrain load on devices

   The NSIS architecture should give the ability to constrain the load
   (CPU load, memory space, signaling bandwidth consumption and
   signaling intensity) on devices where it is needed. One of the
   reasons is that the protocol handling should have a minimal impact
   on interior (core) nodes.

   This can be achieved by many different methods. Examples, and this
   are only examples, include message aggregation, by ignoring
   signaling message, header compression, or minimizing functionality.
   The framework may choose any method as long as the requirement is
   met.

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5.6.9 Highest possible network utilization

   There are networking environments that require high network
   utilization for various reasons, and the signaling protocol should
   to its best ability support high resource utilization while
   maintaining appropriate QoS.

   In networks where resources are very expensive (as is the case for
   many wireless networks), efficient network utilization is of
   critical financial importance.  On the other hand there are other
   parts of the network where high utilization is not required.



5.7 Flexibility


   This section lists the various ways the protocol can flexibly be
   employed.

5.7.1 Aggregation capability, including the capability to select and
     change the level of aggregation.

5.7.2 Flexibility in the placement of the QoS initiator

   It might be the sender or the receiver of content. But also network-
   initiated reservations are required in various scenarios.

5.7.3 Flexibility in the initiation of re-negotiation (QoS change
     requests)

   Again the sender or the receiver of content might initiate a re-
   negotiation due to various reasons, such as local resource shortage
   (CPU, memory on end-system) or a user changed application
   preference/profiles. But also network-initiated re-negotiation is
   required in cases, where the network is not able to further
   guarantee resources etc.

5.7.4 Uni / bi-directional reservation

   Both uni-directonal as well as bi-direction reservations must be
   possible.

5.8 Security

   This section discusses security-related requirements. First a list
   of security threats is given.



5.8.1 The QoS protocol must provide strong authentication

   A QoS protocol must make provision for enabling various entities to


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               Requirements for QoS Signaling Protocols       May 2002

   be authenticated against each other using data origin and/or entity
   authentication. The QoS protocol must enable mutual authentication
   between the two communicating entities.  The term strong
   authentication points to the fact that weak plain-text password
   mechanisms must not be used for authentication.

5.8.2 The QoS protocol must provide means to authorize resource
     requests

   This requirement demands a hook to interact with a policy entity to
   request authorization data. This allows an authenticated entity to
   be associated with authorization data and to verify the resource
   request. Authorization prevents reservations by unauthorized
   entities, reservations violating policies, theft of service and
   additionally limits denial of service attacks against parts of the
   network or the entire network. Additionally it might be helpful to
   provide some means to inform other protocols of participating nodes
   within the same administrative domain about a previous successful
   authorization event.

5.8.3 The QoS signaling messages must provide integrity protection.

   The integrity protection of the transmitted signaling messages
   prevent an adversary from modifying parts of the QoS signaling
   message and from mounting denial of service attacks against network
   elements participating in the QoS protocol.

5.8.4 The QoS signaling messages must be replay protected.

   To prevent replay of previous signaling messages the QoS protocol
   must provide means to detect old messages. A solution must cover
   issues of synchronization problems in the case of a restart or a
   crash of a participating network element. The use of replay
   mechanism apart from sequence numbers should be investigated.

5.8.5 The QoS signaling protocol must allow for hop-by-hop security.

   Hop-by-Hop security is a well known and proven concept in QoS
   protocols that allows intermediate nodes that actively participate
   in the QoS protocol to modify the messages as required by the QoS
   processing. Note that this requirement does not exclude end-to-end
   or network-to-network security of a QoS reservation request. End-to-
   end security between the initiator and the responder may be used to
   provide protection of non-mutable data fields. Network-to-network
   security refers to the protection of messages over various hops but
   not in an end-to-end manner i.e. protected over a particular
   network.

5.8.6 The QoS protocol should allow identity confidentiality and
     location privacy.

   Identity confidentiality enables privacy and avoids profiling of
   entities by adversary eavesdropping the signaling traffic along the
   path. The identity used in the process of authentication may also be

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               Requirements for QoS Signaling Protocols       May 2002

   hidden to a limited extent from a network to which the initiator is
   attached. It is however required that the identity provide enough
   information for the access network to collect accounting data.
   Location privacy is an issue for the initiator who triggers the QoS
   protocol. In some scenarios the initiator may not be willing to
   reveal location information to the responder.

5.8.7 The QoS protocol should prevent denial-of-service attacks against
     signaling entities.

   To effectively prevent denial-of-service attacks the QoS protocol
   and the used security mechanisms should not force to do heavy
   computation to verify a resource request prior authenticating the
   requesting entity. Additionally the QoS protocol and the used
   security mechanisms should not require large resource consumption
   (for example main memory or other additional message exchanges)
   before a successful authentication was done.

5.8.8 The QoS protocol should support confidentiality of signaling
     messages.

   Based on the signaling information exchanged between nodes
   participating in the QoS protocol an adversary may learn both the
   identities and the content of the QoS messages. To prevent this from
   happening, confidentiality of the QoS requests in a hop-by-hop
   manner should be provided. Note that hop-by-hop is always required
   whenever entities actively participating in the protocol must be
   able to read and eventually modify the content of the QoS messages.
   This does not exclude the case where one or more network elements
   are not required to read the information of the transmitted QoS
   messages.

5.8.9 The QoS protocol should provide hooks to interact with protocols
     that allow the negotiation of authentication and key management
     protocols.

   The negotiation of an authentication and key management protocols
   within the QoS protocol is outside the scope of the QoS protocol.
   This requirement originates from the fact that more than one key
   management protocol may be used to provide security associations. So
   both entities must be capable to use the same protocol which may be
   difficult in a mobile environment with different requirements and
   different protocols. The goal of such a negotiation step is to
   determine which authentication and key management protocol to use is
   executed prior to the execution of the chosen key management
   protocol. The used key management protocol must however be able to
   create a security association that matches with the one used in the
   QoS protocol. A QoS protocol should however provide a way to
   interact with these negotiation protocols.

5.8.10 The QoS protocol should provide means to interact with key
     management protocols



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               Requirements for QoS Signaling Protocols       May 2002

   Key management protocols typically require a larger number of
   messages to be transmitted to allow a session key and the
   corresponding security association to be derived. To avoid the
   complex issue of mapping individual authentication and key
   management protocols to a QoS protocol such a protocol is outside
   the scope of the QoS protocol. Although the key management protocol
   may be independent there must be a way for the QoS protocol to
   exploit existing security associations to avoid executing a separate
   key management protocol (or instance of the same protocol) for
   protocols that closely operate together. If no such security
   association exists then there should be means for the QoS protocol
   to trigger a key management protocol to dynamically create the
   required security associations.

5.9 Mobility

5.9.1 Allow efficient QoS re-establishment after handover

   Handover is an essential function in wireless networks. After
   handover, QoS may need to be completely or partially re-established
   due to route changes. The re-establishment may be requested by the
   mobile node itself or triggered by the access point that the mobile
   node is attached to.  In the first case, the QoS signalling should
   allow efficient QoS re-establishment after handover.  Re-
   establishment of QoS after handover should be as quick as possible
   so that the mobile node does not experience service interruption or
   QoS degradation. The re-establishment should be localized, and not
   require end-to-end signalling, if possible.

TBD

5.10    Interworking with other protocols and techniques


   Hooks must be provided to enable efficient interworking between
   various protocols and techniques including:

5.10.1 Interworking with IP tunneling

   IP tunneling for various applications must be supported. More
   specifically tunneling for IPSec tunnels are of importance. This
   mainly impacts the identification of flows. Additionally, care needs
   to be taken using IPSec for signaling message.


5.10.2 The solution should not constrain either to IPv4 or IPv6

5.10.3 Independence from charging model

   Signaling must not be constrained by charging models or the charging
   infrastructure used. However, the end-system should be able to query
   current pay statistics and to specify user cost functions.

5.10.4 The QoS protocol should provide hooks for AAA protocols



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               Requirements for QoS Signaling Protocols       May 2002

   The security mechanism should be developed with respect to be able
   to collect usage records from one or more network elements.

5.11    Operational

5.11.1 Ability to assign transport quality to signaling messages
   The NSIS architecture should allow the network operator to assign
   the NSIS protocol messages a certain transport quality. As signaling
   opens up for possible denial-of-service attacks, this requirement
   gives the network operator a mean, but also the obligation, to
   trade-off between signaling latency and the impact (from the
   signaling messages) on devices within his/her network. From protocol
   design this requirement states that the protocol messages should be
   detectable, at least where the control and assignment of the
   messages priority is done.

6  The MUSTs, SHOULDs, and MAYs

   In order to prioritize the various requirements from Section 5, we
   define different 'parts of the network'. In the different parts of
   the network a particular requirement might have a different
   priority.

   The parts of the networks we differentiate are the host-to-first
   router, the access network, and the core network. The host to first
   router part includes all the layer 2 technologies to access to the
   Internet. In many cases, there is an application and/or user running
   on the host initiating QoS signaling. The access network can be
   characterized by low capacity links, meadium speed IP processing
   capabilities, and it might consist of a complete layer 2 network as
   well. The core network characteristics include high-speed forwarding
   capacities and interdomain QoS issues. All of them are not strictly
   defined and should not be regarded as that, but should give a
   feeling about where in the network we have different requirements
   concerning QoS signaling.

   Note that the requirement titles are listed for better reading.

   5.1  Architecture and Design Goals
   5.1.1 Applicability for different QoS technologies.
   5.1.2 Resource availability information on request
   5.1.3 Modularity
   5.1.4 Decoupling of protocol and information it is carrying
   5.1.5 Reuse of existing QoS provisioning
   5.1.6 Independence of signaling and provisioning paradigm

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.1.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.1.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.1.3                 |             |             |            |

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               Requirements for QoS Signaling Protocols       May 2002

   ----------------------+-------------+-------------+------------+
   5.1.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.1.5                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.1.6                 |             |             |            |
   ----------------------+-------------+-------------+------------+


   5.2  Signaling Flows
   5.2.1 Free placement of QoS Initiator and QoS Controllers functions

   5.2.2 No constraint of the QoS signaling and QoS Controllers to be
   in the data path.
   5.2.3 Concealment of topology and technology information
   5.2.4 Optional transparency of QoS signaling to network

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.2.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.2.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.2.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.2.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.3  Additional information beyond signaling of QoS information
   5.3.1 Explicit release of resources
   5.3.2 Possibility for automatic release of resources after failure
   5.3.3 Possibility for automatic re-setup of resources after recovery
   5.3.4 Prompt notification of QoS violation in case of error /
   failure to QoS Initiator and QoS Controllers
   5.3.5 Feedback about success of request for QoS guarantees
   5.3.6 Allow local QoS information exchange between nodes of the same
   administrative domain

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.3.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.3.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.3.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.3.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.3.5                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.3.6                 |             |             |            |
   ----------------------+-------------+-------------+------------+

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   5.4  Layering

   5.4.1  The signaling protocol and QoS control information should be
   application independent.

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.4.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.5  QoS Control Information

   5.5.1 Mutability information on parameters
   5.5.2 Possibility to add and remove local domain information
   5.5.3 Independence of reservation identifier
   5.5.4 Seamless modification of already reserved QoS
   5.5.5 Signaling must support quantitative, qualitative, and relative
   QoS specifications

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.5.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.5.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.5.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.5.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.5.5                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.6  Performance

   5.6.1 Scalability in the number of messages received by a signaling
   communication partner (QoS initiator and controller)
   5.6.2 Scalability in number of hand-offs
   5.6.3 Scalability in the number of interactions for setting up a
   reservation
   5.6.4 Scalability in the number of state per entity (QoS initiators
   and QoS controllers)
   5.6.5 Scalability in CPU use (end terminal and intermediate nodes)
   5.6.6 Low latency in setup
   5.6.7 Allow for low bandwidth consumption for signaling protocol
   5.6.8 Ability to constrain load on devices
   5.6.9 Highest possible network utilization

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.6.1                 |             |             |            |


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               Requirements for QoS Signaling Protocols       May 2002

   ----------------------+-------------+-------------+------------+
   5.6.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.5                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.6                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.7                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.8                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.6.9                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.7  Flexibility

   5.7.1 Aggregation capability, including the capability to select and
   change the level of aggregation.
   5.7.2 Flexibility in the placement of the QoS initiator
   5.7.3 Flexibility in the initiation of re-negotiation (QoS change
   requests)
   5.7.4 Uni / bi-directional reservation

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.7.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.7.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.7.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.7.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.8 Security

   5.8.1 The QoS protocol must provide strong authentication
   5.8.2 The QoS protocol must provide means to authorize resource
   requests
   5.8.3 The QoS signaling messages must provide integrity protection.
   5.8.4 The QoS signaling messages must be replay protected.
   5.8.5 The QoS signaling protocol must allow for hop-by-hop security.
   5.8.6 The QoS protocol should allow identity confidentiality and
   location privacy.
   5.8.7 The QoS protocol should prevent denial-of-service attacks
   against signaling entities.
   5.8.8 The QoS protocol should support confidentiality of signaling
   messages.


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               Requirements for QoS Signaling Protocols       May 2002

   5.8.9 The QoS protocol should provide hooks to interact with
   protocols that allow the negotiation of authentication and key
   management protocols.
   5.8.10 The QoS protocol should provide means to interact with key
   management protocols.

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.8.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.2                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.3                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.4                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.5                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.6                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.7                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.8                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.9                 |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.8.10                |             |             |            |
   ----------------------+-------------+-------------+------------+


   5.9  Mobility

   5.9.1 Allow efficient QoS re-establishment after handover
   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.9.1                 |             |             |            |
   ----------------------+-------------+-------------+------------+

   5.10 Interworking with other protocols and techniques

   5.10.1 Interworking with IP tunneling
   5.10.2 The solution should not constrain either to IPv4 or IPv6

   5.10.3 Independence from charging model
   5.10.4 The QoS protocol should provide hooks for AAA protocols

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.10.1                |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.10.2                |             |             |            |


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               Requirements for QoS Signaling Protocols       May 2002

   ----------------------+-------------+-------------+------------+
   5.10.3                |             |             |            |
   ----------------------+-------------+-------------+------------+
   5.10.4                |             |             |            |
   ----------------------+-------------+-------------+------------+


   5.11 Operational
   5.11.1 Ability to assign transport quality to signaling messages

   ----------------------+-------------+-------------+------------+
                         | host-to-net |   access    |   core     |
   ----------------------+-------------+-------------+------------+
   5.11.1                |             |             |            |
   ----------------------+-------------+-------------+------------+


7  References

   [1] Kempf, J., "Dormant Mode Host Alerting ("IP Paging") Problem
   Statement", RFC 3132, June 2001.

   [2] Chaskar, H., "Requirements of a QoS Solution for Mobile IP",
   draft-ietf-mobileip-qos-requirements-01.txt, Work in Progress,
   August 2001

   [3] Manner. J., et al, "Mobility Related Terminology", draft-manner-
   seamoby-terms-02.txt, Work In Progress, July 2001.

   [4] 3GPP, "General Packet Radio Service (GPRS); Service Description
   Stage 2 v 7.7.0", TS 03.60, June 2001

   [5] 3GPP2, "Network Reference Model for cdma2000 Spread Spectrum
   System, revision B", S.R0005-B, May 2001

   [6] Bradner, S., Mankin, A., "Report of the Next Steps in Signaling
   BOF", draft-bradner-nsis-bof-00.txt, Work in Progress, July 2001

   [7] Partain, D., et al, "Resource Reservation Issues in Cellular
   Radio Access Networks", draft-westberg-rmd-cellular-issues-00.txt,
   Work in Progress, June 2001.

   [8] YESSIR - YEt another Sender Session Internet Reservations,
   http://www.cs.columbia.edupingpan/projects/yessir.html

   [9] Braden, R., Zhang, L., Berson, S., Herzog, A., Jamin, S.,
   "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
   Specification", IETF RFC 2205, 1997.

   [10] Westberg, L., Jacobsson, M., Partain, D., Karagiannis, G.,
   Oosthoek, S., Rexhepi, V., Szabo, R., Wallentin, P., "Resource
   Management in Diffserv Framework", Internet draft, work in progress,
   draft-westberg-rmd-framework-xx.txt, 2002.


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               Requirements for QoS Signaling Protocols       May 2002

   [11] Kempf, J., McCann, P., Roberts, P., "IP Mobility and the CDMA
   Radio Access Network", IETF Draft, draft-kempf-cdma-appl-02.txt,
   Work in progress, September 2001.



8  Appendix: Scenarios/Use cases

   In the following we describe scenarios, which are important to
   cover, and which allow us to discuss various requirements. Some
   regard this as use cases to be covered defining the use of a QoS
   signaling protocol.

8.1 Scenario: Terminal Mobility

   The scenario we are looking at is the case where a mobile terminal
   (MT) changes from one access point to another access point. The
   access points are located in separate QoS domains. We assume Mobile
   IP to handle mobility on the network layer in this scenario and
   consider the various extensions (i.e., IETF proposals) to Mobile IP,
   in order to provide 'fast handover' for roaming Mobile Terminals.
   The goal to be achieved lies in providing, keeping, and adapting the
   requested QoS for the ongoing IP sessions in case of handover.
   Furthermore, the negotiation of QoS parameters with the new domain
   via the old connection might be needed, in order to support the
   different 'fast handover' proposals within the IETF.

   The entities involved in this scenario include a mobile terminal,
   access points, an access network manager, communication partners of
   the MT (the other end(s) of the communication association).
   From a technical point of view, terminal mobility means changing the
   access point of a mobile terminal (MT). However, technologies might
   change in various directions (access technology, QoS technology,
   administrative domain). If the access points are within one specific
   QoS technology (independent of access technology) we call this
   intra-QoS technology handoff. In the case of an inter-QoS technology
   handoff, one changes from e.g. a DiffServ to an IntServ domain,
   however still using the same access technology. Finally, if the
   access points are using different access technologies we call it
   inter-technology hand-off.

   The following issues are of special importance in this scenario:

   1) Handoff decision

   - The QoS management requests handoff. The QoS management can decide
   to change the access point, since the traffic conditions of the new
   access point are better supporting the QoS requirements. The metric
   may be different (optimized towards a single or a group/class of
   users). Note that the MT or the network (see below) might trigger
   the handoff.

   - The mobility management forces handoff. This can have several
   reasons. The operator optimizes his network, admission is no longer


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               Requirements for QoS Signaling Protocols       May 2002

   granted (e.g. emptied prepaid condition). Or another example is when
   the MT is reaching the focus of another base station. However, this
   might be detected via measurements of QoS on the physical layer and
   is therefore out of scope of QoS signaling in IP. Note again that
   the MT or the network (see below) might trigger the handoff.

   - This scenario shows that local decisions might not be enough. The
   rest of the path to the other end of the communication needs to be
   considered as well. Hand-off decisions in a QoS domain, does not
   only depend on the local resource availability, e.g., the wireless
   part, but involves the rest of the path as well. Additionally,
   decomposition of an end-to-end reservation might be needed, in order
   to change only parts of it.

   2) Trigger sources

   - Mobile terminal: If the end-system QoS management identifies
   another (better-suited) access point, it will request the handoff
   from the terminal itself. This will be especially likely in the case
   that two different provider networks are involved. Another important
   example is when the current access point bearer disappears (e.g.
   removing the Ethernet cable). In this case, the QoS initiator is
   basically located on the mobile terminal.

   - Network (access network manager): Sometimes, the handoff trigger
   will be issued from the network management to optimize the overall
   load situation. Most likely this will result in changing the base-
   station of a single providers network. Most likely the QoS initiator
   is located on a system within the network.

   3) Integration with other protocols

   - Interworking with other protocol must be considered in one or the
   other form. E.g., it might be worth combining QoS signaling between
   different QoS domains with mobility signaling at hand-over.

   4) Handover rates

   In mobile networks, the admission control process has to cope with
   far more admission requests than call setups alone would generate.
   For example, in the GSM (Global System for Mobile communications)
   case, mobility usually generates an average of one to two handovers
   per call. For third generation networks (such as UMTS), where it is
   necessary to keep radio links to several cells simultaneously
   (macro-diversity), the handover rate is significantly higher (see
   for example [11])

   5) Fast reservations

   Handover can also cause packet losses. This happens when the
   processing of an admission request causes a delayed handover to the
   new base station. In this situation, some packets might be
   discarded, and the overall speech quality might be degraded
   significantly. Moreover, a delay in handover may cause degradation

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               Requirements for QoS Signaling Protocols       May 2002

   for other users. In the worst case scenario, a delay in handover may
   cause the connection to be dropped if the handover occurred due to
   bad air link quality. Therefore, it is critical that QoS signalling
   in connection with handover be carried out very quickly.

   6) Call blocking in case of overload

   Furthermore, when the network is overloaded, it is preferable to
   keep reservations for previously established flows while blocking
   new requests. Therefore, the resource reservation requests in
   connection with handover should be given higher priority than new
   requests for resource reservation.

8.2 Scenario: Cellular Networks

   In this scenario, the user is using the packet service of a 3rd
   generation cellular system, e.g. UMTS. The region between the End
   Host and the edge node connecting the cellular network to another
   QoS domain (e.g. the GGSN in UMTS or the PDSN in 3GPP2) is
   considered to be a single QoS domain [4][5].

   The issues in such an environment regarding QoS include:

   1) Cellular systems provide their own QoS technology with
   specialized parameters to co-ordinate the QoS provided by both the
   radio access and wired access network. For example, in a UMTS
   network, one aspect of GPRS is that it can be considered as a QoS
   technology; provisioning of QoS within GPRS is described mainly in
   terms of calling UMTS bearer classes.  This QoS technology needs to
   be invoked with suitable parameters when a request for QoS is
   triggered by higher layers, and this therefore involves mapping the
   requested IP QoS onto these UMTS bearer classes. This request for
   resources might be triggered by IP signaling messages that pass
   across the cellular system, and possibly other QoS domains, to
   negotiate for network resources. Typically, cellular system specific
   messages invoke the underlying cellular system QoS technology in
   parallel with the IP QoS negotiation, to allocate the resources
   within the cellular system.

   2) The placement of QoS initiators and QoS controllers (terminology
   in the framework given here). The QoS initiator could be located at
   the End Host (triggered by applications), the GGSN/PDSN, or at a
   node not directly on the data path, such as a bandwidth broker. In
   the second case, the GGSN/PDSN could either be acting as a proxy on
   behalf of an End Host with little capabilities, and/or managing
   aggregate resources within its QoS domain (the UMTS core network).
   The IP signaling messages are interpreted by the QoS controllers,
   which may be located at the GGSN/PDSN, and in any QoS sub-domains
   within the cellular system.

   3) Initiation of IP-level QoS negotiation. IP-level QoS re-
   negotiation may be initiated by either the End Host, or by the
   network, based on current network loads, which might change
   depending on the location of the end host.

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   4) The networks are designed and mainly used for speech
   communication (at least so far).

   Note that in comparison to the former scenario, the emphasis is much
   less on the mobility aspects, because mobility is mainly handled on
   the lower layer.

8.3 Scenario: UMTS access

   The UMTS access scenario is shown in figure 3. The Proxy-Call State
   Control Function/Policy Control Function (P-CSCF/PCF) is the
   outbound SIP proxy of the visited domain, i.e. the domain where the
   mobile user wants to set-up a call. The Gateway GPRS Support Node
   (GGSN) is the egress router of the UMTS domain and connects the UMTS
   access network to the Edge Router (ER) of the core IP network. The
   P-CSCF/PCF communicates with the GGSN via the COPS protocol [4]. The
   User Equipment (UE) consists of a Mobile Terminal (MT) and Terminal
   Equipment (TE), e.g. a laptop.


                           +--------+
                +----------| P-CSCF |-------> SIP signaling
               /           +--------+
              / SIP            :
             :             +--------+   NSIS  +----------------+
             :             |  PCF   |---------| QoS Controller |
             :             +--------+         +----------------+
             :                 :
             :                 : COPS
             :                 :
           +----+          +--------+      +----+
           | UE |----------|  GGSN  |------| ER |
           +----+          +--------+      +----+

                      Figure 1: UMTS access scenario

   In this scenario the GGSN has the role of Access Gate. According to
   3GPP standardization, the PCF is responsible for the policy-based
   control of the end-user service in the UMTS access network (i.e.
   from UE to GGSN). In the current UMTS release R.5, the PCF is part
   of the P-CSCF, but in UMTS R.6 the interface between P-CSCF and PCF
   may evolve to an open standardized interface. In any case the PCF
   has all required QoS information for per-flow admission control in
   the UMTS access network (which it gets from the P-CSCF and/or GGSN).
   Thus the PCF would be the appropriate entity to host the
   functionality of QI, initiating the "NSIS" QoS signaling towards the
   core IP network. The PCF/P-CSCF has to do the mapping from codec
   type (derived from SIP/SDP signaling) to IP traffic descriptor. SDP
   extensions to explicitly signal QoS information [7] are useful to
   avoid the need to store codec information in the PCF and to allow
   for more flexibility and accurate description of the QoS traffic
   parameters. The PCF also controls the GGSN to open and close the


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               Requirements for QoS Signaling Protocols       May 2002

   gates and to configure per-flow policers, i.e. to authorize or
   forbid user traffic.

   The QC is (of course) not part of the standard UMTS architecture.
   However, to achieve end-to-end QoS a QC is needed such that the PCF
   can request a QoS connection to the IP network. As in the previous
   example, the QC could manage a set of pre-provisioned resources in
   the IP network, i.e. bandwidth pipes, and the QC performs per-flow
   admission control into these pipes. In this way, a connection can be
   made between two UMTS access networks, and hence, end-to-end QoS can
   be achieved. In this case the QI and QC are clearly two separate
   entities.
   This use case clearly illustrates the need for an "NSIS" QoS
   signaling protocol between QI and QC. An important application of
   such a protocol may be its use in the inter-connection of UMTS
   networks over an IP backbone.

8.4 Wired part of wireless network

   A wireless network, seen from a QoS domain perspective, usually
   consists of three parts: a wireless interface part (the "radio
   interface"), a wired part of the wireless network (i.e., Radio
   Access Network) and the backbone of the wireless network, as shown
   in Figure 2. Note that this figure should not be seen as an
   architectural overview of wireless networks but rather as showing
   the conceptual QoS domains in a wireless network.

   In this scenario, a mobile host can roam and perform a handover
   procedure between base stations/access routers. In this scenario the
   NSIS QoS protocol can be applied between a base station and the
   gateway (GW).  In this case a GW can also be considered as a local
   handover anchor point. Furthermore, in this scenario the NSIS QoS
   protocol can also be applied either between two GWs, or between two
   edge routers (ER).

                             |--|
                             |GW|
      |--|                   |--|
      |MH|---                  .
      |--|  / |-------|        .
           /--|base   | |--|   .
              |station|-|ER|....
              |-------| |--|   .  |--| back- |--|  |---|
   |----|

   ...|ER|.......|ER|..|BGW|.."Internet"..|host|
           -- |-------| |--|   .  |--| bone  |--|  |---|
   |----|
      |--| \  |base   |-|ER|...     .
      |MH|  \ |station| |--|        .
      |--|--- |-------|             .          MH  = mobile host
                                 |--|          ER  = edge router
         <---->                  |GW|          GW  = gateway
        Wireless link            |--|          BGW = border gateway

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               Requirements for QoS Signaling Protocols       May 2002

                                               ... = interior nodes
               <------------------->
         Wired part of wireless network

      <---------------------------------------->
                   Wireless Network

      Figure 2. QoS architecture of wired part of wireless network

   Each of these parts of the wireless network impose different issues
   to be solved on the QoS signaling solution being used:


   * Wireless interface: The solution for the air interface link
     has to ensure flexibility and spectrum efficient transmission
     of IP packets.  However, this link layer QoS can be solved in
     the same way as any other last hop problem by allowing a
     host to request the proper QoS profile.

   * Wired part of the wireless network:  This is the part of
     the network that is closest to the base stations/access
     routers.  It is an IP network although some parts logically
     perform tunneling of the end user data. In cellular networks,
     the wired part of the wireless network is denoted as a
     radio access network.

     This part of the wireless network has different
     characteristics when compared to traditional IP networks:

         1. The network supports a high proportion of real-time
            traffic.  The majority of the traffic transported in the
            wired part of the wireless network is speech, which is
            very sensitive to delays and delay variation (jitter).

         2. The network must support mobility.  Many wireless
            networks are able to provide a combination of soft
            and hard handover procedures.  When handover occurs,
            reservations need to be established on new paths.
            The establishment time has to be as short as possible
            since long establishment times for reservations degrade
            the performance of the wireless network.  Moreover,
            for maximal utilization of the radio spectrum, frequent
            handover operations are required.

         3. These links are typically rather bandwidth-limited.

         4. The wired transmission in such a network contains a
            relatively high volume of expensive leased lines.
            Overprovisioning might therefore be prohibitively
            expensive.

         5. The radio base stations are spread over a wide
            geographical area and are in general situated a large
            distance from the backbone.

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   * Backbone of the wireless network: the requirements imposed
     by this network are similar to the requirements imposed by
     other types of backbone networks.

   Due to these very different characteristics and requirements, often
   contradictory, different QoS signalling solutions might be needed in
   each of the three network parts.

8.5 Scenario: Session Mobility

   In this scenario, a session is moved from one end-system to another.
   Ongoing sessions are kept and QoS parameters need to be adapted,
   since it is very likely that the new device provides different
   capabilities. Note that it is open which entity initiates the move,
   which implies that the QoS initiator might be triggered by different
   entities.

   User mobility (i.e., a user changing the device and therefore moving
   the sessions to the new device) is considered to be a special case
   within the session mobility scenario.

   Note that this scenario is different from terminal mobility. Not the
   terminal (end-system) has moved to a different access point. Both
   terminals are still connected to an IP network at their original
   points.

   The issues include:

   1) Keeping the QoS guarantees negotiated implies that the end-
   point(s) of communication are changed without changing the
   reservations.

   2) The trigger of the session move might be the user or any other
   party involved in the session.

8.6 Scenario: QoS reservations/negotiation from access to core network

   The scenario includes the signaling between access networks and core
   networks in order to setup and change reservations together with
   potential negotiation.

   The issues to be solved in this scenario are different from previous
   ones.

   1) The entity of reservation is most likely an aggregate.

   2) The time scales of reservations might be different (long living
   reservations of aggregates, rarer re-negotiation).

   3) The specification of the traffic (amount of traffic), a
   particular QoS is guaranteed for, needs to be changed. E.g., in case
   additional flows are added to the aggregate, the traffic


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               Requirements for QoS Signaling Protocols       May 2002

   specification of the flow needs to be added if it is not already
   included in the aggregates specification.

   4) The flow specification is more complex including network
   addresses and sets of different address for the source as well as
   for the destination of the flow.

8.7 Scenario: QoS reservation/negotiation over administrative
    boundaries

   Signaling between two or more core networks to provide QoS is
   handled in this scenario. This might also include access to core
   signaling over administrative boundaries. Compared to the previous
   one it adds the case, where the two networks are not in the same
   administrative domain. Basically, it is the inter-domain/inter
   provider signaling which is handled in here.

   The domain boundary is the critical issue to be resolved. Which as
   various flavors of issues a QoS signaling protocol has to be
   concerned with.

   1) Competing administrations: Normally, only basic information
   should be exchanged, if the signaling is between competing
   administrations. Specifically information about core network
   internals (e.g., topology, technology, etc.) should not be
   exchanged. Some information exchange about the "access points" of
   the core networks (which is topology information as well) may need
   to be exchanged, because it is needed for proper signaling.

   2) Additionally, as in scenario 4, signaling most likely is based on
   aggregates, with all the issues raise there.

   3) Authorization: It is critical that the QoS initiator is
   authorized to perform a QoS path setup.

   4) Accountability: It is important to notice that signaling might be
   used as an entity to charge money for, therefore the interoperation
   with accounting needs to be available.

8.8 Scenario: QoS signaling between PSTN gateways and backbone routers

   A PSTN gateway (i.e., host) requires information from the network
   regarding its ability to transport voice traffic across the network.
   The voice quality will suffer due to packet loss, latency and
   jitter. Signaling is used to identify and admit a flow for which
   these impairments are minimized.  In addition, the disposition of
   the signaling request is used to allow the PSTN GW to make a call
   routing decision before the call is actually accepted and delivered
   to the final destination.

   PSTN gateways may handle thousands of calls simultaneously and there
   may be hundreds of PSTN gateways in a single provider network. These
   numbers are likely to increase as the size of the network increases.
   The point being that scalability is a major issue.


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   There are several ways that a PSTN gateway can acquire assurances
   that a network can carry its traffic across the network. These
   include:

     1. Over-provisioning a high availability network.
     2. Handling admission control through some policy server
        that has a global view of the network and its resources.
     3. Per PSTN GW pair admission control.
     4. Per call admission control (where a call is defined as
        the 5 tuple used to carry a single RTP flow).

   Item 1 requires no signaling at all and is therefore outside the
   scope of this working group.

   Item 2 is really a better informed version of 1, but it is also
   outside the scope of this working group as it relies on a particular
   telephony signaling protocol rather than a packet admission control
   protocol.

   Item 3 is initially attractive as it appears to have reasonable
   scaling properties, however, its scaling properties only are
   effective in cases where there are relatively few PSTN GWs. In the
   more general case were a PSTN GW reduces to a single IP phone
   sitting behind some access network, the opportunities for
   aggregation are reduced and the problem reduces to item 4.

   Item 4 is the most general case. However, it has the most difficult
   scaling problems. The objective here is to place the requirements on
   Item 4 such that a scalable per-flow admission control protocol or
   protocol suite may be developed.

   The case where per-flow signaling extends to individual IP end-
   points allows the inclusion of IP phones on cable, DSL, wireless or
   other access networks in this scenario.

   Call Scenario

   A PSTN GW signals end-to-end for some 5 tuple defined flow a
   bandwidth and QoS requirement. Note that the 5 tuple might include
   masking/wildcarding. The access network admits this flow according
   to its local policy and the specific details of the access
   technology.

   At the edge router (i.e., border node), the flow is admitted, again
   with an optional authentication process, possibly involving an
   external policy server.  Note that the relationship between the PSTN
   GW and the policy server and the routers and the policy server is
   outside the scope of NSIS. The edge router then admits the flow into
   the core of the network, possibly using some aggregation technique.

   At the interior nodes, the NSIS host-to-host signaling should either
   be ignored or invisible as the Edge router performed the admission
   control decision to some aggregate.


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   At the inter-provider router (i.e., border node), again the NSIS
   host-to-host signaling should either be ignored or invisible as the
   Edge router has performed an admission control decision about an
   aggregate across a carrier network.

8.9 PSTN trunking gateway

   One of the use cases for the NSIS signaling protocol is the scenario
   of interconnecting PSTN gateways with an IP network that supports
   QoS.
   Four different scenarios are considered here.
     1.        In-band QoS signaling is used. In this case the Media Gateway
        (MG) will be acting as the QoS Initiator and the Edge Router
        (ER) will be the QoS Controller. Hence, the ER should do
        admission control (into pre-provisioned traffic trunks) for the
        individual traffic flows. This scenario is not further
        considered here.
     2.        Out-of-band signaling in a single domain, the QoS Controller is
        integrated in the MGC. In this case no NSIS protocol is
        required.
     3.        Out-of-band signaling in a single domain, the QoS Controller is
        a separate box. In this case NSIS signaling is used between the
        MGC and the QoS Controller.
     4.        Out-of-band signaling between multiple domains, the QoS
        Controller (which may be integrated in the MGC) triggers the
        QoS Controller of the next domain.

   When the out-of-band QoS signaling is used the Media Gateway
   Controller (MGC) will be acting as the QoS Initiator.

   In the second scenario the voice provider manages a set of traffic
   trunks that are leased from a network provider. The MGC does the
   admission control in this case. Since the QoS Controller acts both
   as a QoS Initiator and a QoS Controller, no NSIS signaling is
   required. This scenario is shown in figure 1.

      +-------------+    ISUP/SIGTRAN     +-----+              +-----+
      | SS7 network |---------------------| MGC |--------------| SS7 |
      +-------------+             +-------+-----+---------+    +-----+
            :                    /           :             \
            :                   /            :              \
            :                  /    +--------:----------+    \
            :          MEGACO /    /         :           \    \
            :                /    /       +-----+         \    \
            :               /    /        | NMS |          \    \
            :              /     |        +-----+          |     \
            :              :     |                         |     :
     +--------------+  +----+    |   bandwidth pipe (SLS)  |  +----+
     | PSTN network |--| MG |--|ER|======================|ER|-| MG |--
     +--------------+  +----+     \                       /   +----+
                                   \     QoS network     /
                                    +-------------------+


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               Requirements for QoS Signaling Protocols       May 2002

                 Figure 1: PSTN trunking gateway scenario

   In the third scenario, the voice provider does not lease traffic
   trunks in the network. Another entity may lease traffic trunks and
   may use a QoS Controller to do per-flow admission control. In this
   case the NSIS signaling is used between the MGC and the QoS
   Controller, which is a separate box here. Hence, the MGC acts only
   as a QoS Initiator. This scenario is depicted in figure 2.


      +-------------+    ISUP/SIGTRAN     +-----+              +-----+
      | SS7 network |---------------------| MGC |--------------| SS7 |
      +-------------+             +-------+-----+---------+    +-----+
            :                    /           :             \
            :                   /         +-----+           \
            :                  /          | QC  |            \
            :                 /           +-----+             \
            :                /               :                 \
            :               /       +--------:----------+       \
            :       MEGACO :       /         :           \       :
            :              :      /       +-----+         \      :
            :              :     /        | NMS |          \     :
            :              :     |        +-----+          |     :
            :              :     |                         |     :
     +--------------+  +----+    |   bandwidth pipe (SLS)  |  +----+
     | PSTN network |--| MG |--|ER|======================|ER|-| MG |--
     +--------------+  +----+     \                       /   +----+
                                   \     QoS network     /
                                    +-------------------+

                 Figure 2: PSTN trunking gateway scenario

   In the fourth scenario multiple transport domains are involved. In
   the originating network either the MGC may have an overview on the
   resources of the overlay network or a separate QoS Controller will
   have the overview. Hence, depending on this either the MGC or the
   QoS Controller of the originating domain will contact the QoS
   Controller of the next domain. The MGC always acts as a QoS
   Initiator and may also be acting as a QoS Controller in the first
   domain.

8.10    Scenario: Application request end-to-end QoS path from the
    network

   This is actually the most easy case, nevertheless might be most
   often used in terms of number of users. So multimedia application
   requests a guaranteed service from an IP network. We assume here
   that the application is somehow able to specify the network service.
   The characteristics here are that many hosts might do it, but that
   the requested service is low capacity (bounded by the access line).
   Additionally, we assume no mobility and standard devices.




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9  Acknowledgments

   Quite a number of people have been involved in the discussion of the
   draft, adding some ideas, requirements, etc. We list them without a
   guarantee on completeness: Changpeng Fan (Siemens), Krishna Paul
   (NEC), Maurizio Molina (NEC), Mirko Schramm (Siemens), Andreas
   Schrader (NEC), Hannes Hartenstein (NEC), Ralf Schmitz (NEC),
   Juergen Quittek (NEC), Morihisa Momona (NEC), Holger Karl (Technical
   University Berlin), Xiaoming Fu (Technical University Berlin), Hans-
   Peter Schwefel (Siemens), Mathias Rautenberg (Siemens), Christoph
   Niedermeier (Siemens), Andreas Kassler (University of Ulm), Ilya
   Freytsis.

   Some text and/or ideas for text, requirements, scenarios have been
   taken from a draft written by the following authors: David Partain
   (Ericsson), Anders Bergsten (Telia Research), Marc Greis (Nokia),
   Georgios Karagiannis (Ericsson), Jukka Manner (University of
   Helsinki), Ping Pan (Juniper), Vlora Rexhepi (Ericsson), Lars
   Westberg (Ericsson), Haihong Zheng (Nokia). Some of those have
   actively contributed new text to the draft as well.

   Another draft impacting this draft has been written by Sven Van den
   Bosch, Maarten Buchli, and Danny Goderis. These people contributed
   also with new text.

10 Author's Addresses

   Marcus Brunner (Editor)
   NEC Europe Ltd.
   Network Laboratories
   Adenauerplatz 6
   D-69115 Heidelberg
   Germany
   E-Mail: brunner@ccrle.nec.de (contact)

   Robert Hancock, Eleanor Hepworth
   Roke Manor Research Ltd
   Romsey, Hants, SO51 0ZN
   United Kingdom
   E-Mail: [robert.hancock|eleanor.hepworth]@roke.co.uk

   Cornelia Kappler
   Siemens AG
   Berlin  13623
   Germany
   E-Mail: cornelia.kappler@icn.siemens.de

   Hannes Tschofenig
   Siemens AG
   Otto-Hahn-Ring 6
   81739 Munchen
   Germany
   Email: Hannes.Tschofenig@mchp.siemens.de


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               Requirements for QoS Signaling Protocols       May 2002

Full Copyright Statement
  Copyright (C) The Internet Society (2000). All Rights Reserved.
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   Open Issues/To Dos

   1) (OPEN) add Scenarios
   Do we need to add, remove, or change the scenarios?
   - added scenario on QoS signalling between PSTN gateways and
   backbone routers
   - added: Application request end-to-end QoS path from the network

   We can what ever scenario we want. The more the better to understand
   the issues. Nevertheless, we have to take care that we are future
   prove as well.

   2) (OPEN) Sender/receiver initiation

   What is the requirement concerning data sender or data receiver or
   both to initiate a QoS request.

   Terminology text added

   open issue, what is a potential req (currently we say "both must be
   possible")

   Proposals:
   1)should be optimized for sender initiated
   2) remove the requirement, because it is not relevant if we allow
   for third party QoS initiators
   3) SHOULD support sender initiated, MAY support reciever initiated

   Issues:

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               Requirements for QoS Signaling Protocols       May 2002

   - does it matter who pays?

   - for sender initiated, can we support implicit signaling
   (bundling the QoS requests with other signaling - registration,
   etc.)?

   - For reciever initiated, do we need protection against spamming -
   how do we protect against unwanted changes?



   3) (CLOSED) Draft organization

   The proposed changes include
   - put all the scenarios into an appendix
   - In Section 6 add text describing 3 different "parts of the
   network"
        -Host to first hop
        -access network
        -core networks
     better names are welcome, but I don't want to be religious about
   it

   - Prioritize the requirements according to the "parts of the
   network" (This means the the tables in Section 6 of the current
   draft will get three colums with the MUST, SHOULDs, and MAYs for
   each requirement

   4) (OPEN) MUSTs, SHOULDs, MAY needs discussion

   5) (CLOSED) Framework text.
   The figures have been removed, because they seamed to be misleading.
   the text has been revisited. I regard the issue closed until we have
   a clear picture about what the NSIS framework draft is about.

   6) (CLOSED) The requirement organization
   I heard some voices on the list that the grouping should be more
   along the lines of host-to-edge, edge to edge etc.
   So far I have not changed it, because I though that the requirements
   heavily depend on the scenario we are looking at.

   closed, by the change in the draft organisation (issue 3)

   7) (OPEN) Hemant Chaskar: Section 3.1, items 1) Handoff decision and
   2) Trigger sources: The handoff decision and trigger sources should
   be out of scope of NSIS. NSIS should rather focus only on
   "establishing" QoS along the packet path after handoff.

   needs more WG discussion, potentially even cross-WG

   8) (OPEN) bi-directional data path setup with one QoS request
   I have not seen consensus on whether to require bi-directional data
   path setup with QoS.


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               Requirements for QoS Signaling Protocols       May 2002

   Q: How can we actually perform bi-directional reservations when the
   forward and reverse paths are not reciprocal, with respect to
   routing topology and routing policy of network domains between
   sender and receiver?

   A: bi-directional data path setup does not need to use the same
   return path as the forwarding path. The only requirement to achieve
   a bi-directional reservation is that the sender for the forwarding
   path is also the receiver for the return path and that the receiver
   for the  forwarding path is also the sender for the return path.


   - The need to ensure that the return path is the same as the
   forwarding path is one of the problems with RSVP, particularly in a
   mobile environment.

   9) (CLOSED) Potential requirement: must be implementable in user
   space (on end hosts)

   has not been included in the req list because it seams to be
   implementation specific.

   10) (CLOSED) Potential requirement: must provide support for
   globally defined services as well as private services (Ruediger)

   replaced by issue 17 and 18, closed

   11) (CLOSED) Potential requirement: Flexibility in the granularity
   of reservation (I don't remember who brought it up, but I assume it
   refers to the flexibility in terms of what size the flow has. Where
   size can be bandwidth etc.)

   The assumption that QoS classes as well as service definitions are
   out of scope for this draft, also the flexibility is.

   12) (CLOSED) text replacing scalability reqs

   "The nsis architecture should give the ability to constrain the load
   (CPU load, memory space, signaling bandwidth consumption and
   signaling intensity) on devices where it is needed. This can be
   achieved by many different methods, for example message aggregation,
   by ignoring signaling message, header compression or minimizing
   functionality. The architecture may choose any of these methods as
   long as the requirement is met."

   Editor: added the draft text, but did not remove scalability reqs

   13) (CLOSED) add operator req "Ability to assign transport quality
   to signaling messages"
   "The nsis architecture should allow the network operator to assign
   the nsis protocol messages a certain transport quality. As signaling
   opens up for possible denial-of-service attacks, this requirement
   gives the network operator a mean, but also the obligation, to
   trade-off between signaling latency and the impact (from the

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               Requirements for QoS Signaling Protocols       May 2002

   signaling messages) on devices within his/her network. From protocol
   design this requirement states that the protocol messages should be
   detectable, at least where the control and assignment of the
   messages priority is done."

   text has been added

   14) (OPEN, dependend on resolution of bi-directional) proposal to
   add "support grouping of microflows (possibly only for feedback)"
   "As a consequence of the optimization for the interactive multimedia
   services, the signaling should allow one unique request for several
   micro flows having the same origination and destination IP
   addresses. This is usually the case for multimedia SIP calls where
   the voice and video micro flows follow the same path. This grouping
   of requests allows optimization of the QoS processing. Note that
   this may be detrimental for the call setup time. The use of grouping
   for microflows may be restricted to teardown and/or notification
   messages when call setup time is a concern."

   open issue: first resolve the bi-directional issue which is somewhat
   related, because it seams to be an optimization as well

   Should not be restrict to teardown and/or notification, it might be
   useful also for the procedure that refreshes reservation states

   15) (CLOSED) Support for preemption of sessions
   -might play into the fault/ error handling case
   -is regarded as service-specific, whether existing sessions can be
   pre-empted
   Conclusion: it is network policy to determine how to do pre-emption,
   not a protocol issue.

   16) (OPEN) Req: 5.1.9 change provisioning into better term, since
   different people understand different thing with provisioning

   open action for Anders

   17) (CLOSED) add assumption that QoS classes/service definitions are
   already known to all the parties involved in signaling before hand
   (before a signalling session even starts

    added text in Section 4.1

   18) (CLOSED) add exclusion of methods, protocols, and ways to
   express QoS
   Even so, this might be covered by saying that we are independent of
   QoS classes and service description etc. (see issue 17), I added two
   points to the exclusion Section 4.2.

   Implications: issue 20, 23,

   19) (CLOSED) remove req 5.2.5 IP fragmentation



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               Requirements for QoS Signaling Protocols       May 2002

   20) (CLOSED) remove req 5.3.2 Ability to signal life-time of a
   reservation

   is regarded service-specific therefore part of the service
   description

   added some reservation life time text service description assumption
   text and removed the req

   21) (CLOSED) remove req 5.5.4 Aggregation method specification

   Concerns
   -QI not able to know the impact of aggregation
   -to far down the implementation/ service definition road
   -leave it to the provider how a service is realized

   removed

   22) (CLOSED) remove 5.3.7 Automatic notification on available
   resources not been granted before

   regarded to complex and is heavily dependend on the service
   description

   removed

   23) (CLOSED) remove 5.5.3 Simple mapping to lower-layer QoS
   provisioning parameters

   this heavily depends on service definition and therefore is out of
   scope of this document

   removed

   24) (CLOSED) Replacing req 5.3.6 "Feedback about the actually
   received level of QoS guarantees" with two requirements: 1) the
   feedback of a request MUST include yes and no (MUST respond yes or
   no) 2) in case of no it MAY include an opaque service-specific
   information about what would be possible

   It is still only one requirement, but the text has been replaced.

   25) (CLOSED) remove req 5.10.3 Combination with Mobility management

   However the integration should not be a priori excluded, there is
   explicitly no statemant about independence of mobility management.

   There is more discussion for the mobility case needed anyway.

   26) (OPEN) interaction of NSIS with seamoby (context transfer and
   CAR discovery)

   27) (CLOSED) remove req 5.5.10 QoS conformance specification


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               Requirements for QoS Signaling Protocols       May 2002

   Motivation: this heavily depends on the service definition and is
   therefore out of scope

   removed

   28) (OPEN) new requirement on "asynchronous events from the network"

   The content of the message might be very service specific, but the
   protocol support for asynchronous events from the network might be a
   valuable requirement. We have something about notification in case
   of errors/failures.

   29) (OPEN) NSIS in case of handovers
   The whole mobility area needs to be defined

   30) (CLOSED) remove 5.1.7 Avoid modularity with large overhead (in
   various dimensions)

   removed because it seams to be obvious

   31) (CLOSED) remove 5.1.8 Possibility to use the signaling protocol
   for existing local technologies

   It is contradictory to 5.1.9 and the intention behind the
   requirement is covered by the requierement that the QoS controller
   can be placed wherever needed.

   32) (CLOSED) add assumption: there are means for discovery of nsis
   entities in order to know the signaling peers (solutions include
   static configuration, or automatically discovered etc.)

   33) (CLOSED) add req " highest possible network utilization"
   "There are networking environments that require high network
   utilization for various reasons, and the signaling protocol should
   to its best ability support high resource utilization while
   maintaining appropriate QoS.

   In networks where resources are very expensive (as is the case for
   many wireless networks), efficient network utilization is of
   critical financial importance.  On the other hand there are other
   parts of the network where high utilization is not required.
   "

   req added

   34) (CLOSED)_difference between "UMTS access scenario" "cellular
   network scenario", and "Wired part of wireless network" (Section
   8.2, 8.3, and 8.4)

   all three are included.
   The only common point between the three scenarios is that they are
   related to cellular networks. Section 8.4 is introducing the
   scenario used  in the radio access network of cellular networks.


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               Requirements for QoS Signaling Protocols       May 2002

   Sections 8.2 and Section 8.3 are discussing other parts of the
   cellular network.

   35) (CLOSED) difference between the two PSTN gateway scenarios
   (Section 8.8 and 8.9)

   currently both are included, they might be merged, sionce one seams
   to be more general than the other

   36) (OPEN) req "Independence of reservation identifier"
   issue here is that this might only be valuable in mobile
   environments, and complicate the protocol for other environemnts.

   there are related issues (37,38,

   37) (OPEN) ownership of a reservation

   The issue here is that a known party owns reservations done in the
   network. (which might include that the party also pays). The
   question arose who is allowed to tear-down, receive asynchronous
   notifications in case of network initiated tear-down, etc.

   This also relates to how certain service granted is
   named/identified.

   38) (OPEN) definition of security threats

   39) (OPEN) simplify security requirements section

   40) (OPEN) add mobility related requirements

   41) (CLOSED) remove req 5.5.1 Mutability information on parameters
   removed because it is service-specific

   42) (OPEN) add an assumption that QoS nmonitoring is application-
   specific and with it out of scope of the WG

   43) (OPEN) asynchronous notification of QoS Initiator, Controller,
   Receiver, there are security issues related. Basically, an ownership
   issue. Nevertheless, an asynch notifcation in case of an error,
   network failure etc. is specifically in areas, where longer lived
   sessions are setup, essential in order to notify upper layes
   (appluications etc. as well.

   44) (OPEN) req 5.1.2 resource availability info on request come back
   to it as soon as we have a more clear idea about service description
   issue

   45) (OPEN) 5.3.4 Possibility for automatic re-setup of resources
   after recovery
   - more thoughts in failure conditions potentially
   - better text
   - operation under overload
   plays into issue 46)

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   46) (OPEN) we need multiple scenario for failure and recovery cases
   to derive requirements. Or a list failre cases might be a start as
   well.

   47) (OPEN) traffic engineering  and route pinning
   I assume this would result in operational type of requirements
   Opinions on that?

   48) (CLOSED) req 5.5.5 remove Multiple levels of detail

   "The QSC should allow for multiple levels of detail in description.
   (Motivation: someone interpreting the request can tune its own level
   of complexity by going down to more or less levels of detail. A
   lightweight implementation within the core could consider only the
   coarsest level.)"

   removed, because it is service-specific

   49) (CLOSED) remove req 5.5.9 Signaling must support quantitative,
   qualitative, and relative QoS specifications

   removed because it is service-specific

   50) (CLOSED) req 5.5.6 remove Ranges in specification

   The QSC should allow for specification of minimum required QoS
   and/or desirable QoS. (Motivation: The QoS Service Classes should
   allow for ranges to be indicated, to minimize negotiation latency
   and suppress error notifications during handover events.)

   removed, is service specific

   51) (CLOSED) remove 5.1.6 Avoid duplication of [sub]domain signaling
   functions

   we might use the requirement text somewhere else:

   Heading: Avoid duplication of [sub]domain signaling functions

   The specification of the NSIS signaling protocol should be optimized
   to avoid duplication of existing [sub]domain QoS signaling and to
   minimize the overall complexity. (Motivation: we don't want to
   introduce duplicate feedback or negotiation mechanisms, or
   complicate the work by including all possible existing QoS signaling
   in some form. The function will be placed in the new part if it has
   to be end-to-end, universal to all network types
   ('simple/lightweight'), or if it has to be protected by upper layer
   security mechanisms.)

   The point here is that the QoS technology (lower layer stuff) gets
   re-used unchanged, and we have new signaling above it. But, in many
   cases the local QoS technology will contain equivalent functions to
   the NSIS-required ones, just in a technology specific form. Examples

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               Requirements for QoS Signaling Protocols       May 2002

   of these functions would be error/QoS violation notifications,
   ability to query for resources and so on. So, there is a danger that
   our 'lightweight' signaling ends up trying to carry all this
   information all over again, and (even worse) that the
   initiator/controller functions have to weigh up nearly equivalent
   information coming from two directions. However, the basic problem
   here is that the boundary between new and re-used stuff is pretty
   shaky. The requirement is trying to scope our problem (a) to
   eliminate the potential overlap, and (b) to keep the new NSIS stuff
   simple.

   However, we are aware that it is very difficult to judge what is
   duplicated, if we want to run the protocol in various environments.



   52) (OPEN) New requirement: interaction with policy
   this most likely is covered by an opaque token for authentication
   dependency on security changes

   53) (OPEN) Section 5.3. Error handling

   Comments:
   1) notification of user in case of unrecoverable errors (has been
   done by notification requirement, or will be done by asynch
   notification, issue 43)
   A description of both types of errors (recoverable, unrecoverable)
   are listed in Section 5.3.4.

   2) hop-by-hop? OR right to the end?

   3) What is potential value to notify about recoverable errors?
   Proposal: not hop by hop, but QoS controller to QoS initiator

   54) (CLOSED) add req 5.1.17. to assumption  "Identification
   requirement"
    assumption say that the discovery of QI, QC, QR is out-of-scope of
   the draft

   55) (CLOSED) add from draft-partain-nsis-requirements-00.txt req
   5.2.2.  Allow local QoS information exchange between two border
   nodes

   "The QoS signalling protocol must be able to exchange local QoS
   information between edge nodes. Local QoS information might, for
   example, be IP addresses, severe congestion notification,
   notification of succesful or erroneous processing of QoS signalling
   messages at one border node.

   In some domains, the NSIS QoS signalling protocol MAY carry
   identification of the ingress and egress edge between the ingress-
   egress edges.  However, the identification of edges should not be
   visible to the end host and only applies within one QoS
   administrative domain.


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               Requirements for QoS Signaling Protocols       May 2002

   "

   Comments:
   - service mapping is more service-specific (layering,tunneling)
   - the scenario to look at is a complicated service description -> in
   part of the network you want to change the message to something more
   easy, and at the other end go back to the more complicated part.
   -QI being everywhere might be enough
   -and we have already a requirement saying that intermediate node
   MUST be able to add/remove domain-specific information to/from
   signaling messages

   56) (CLOSED) add req 5.3.1.3 of draft-partain-..-00
   -already added a req to the scalability section (issue ???), which
   has been provided by Anders

   57) (CLOSED) potentially better title for text from issue 56) e.g.
   (Ɠminimal impact on coreƶ)

   58) (CLOSED) add req 5.3.2 from draft-partain-...-00

   - the fast establishment req is handled by the low setup latency
   req, and the scalability in handover req

   - added the text to the teminal mobility scenario

   - added text " time scale (e.g., handover in mobile environments),"
   to req

   59) (OPEN) add req: ability to deal with severe congestion (req
   5.3.4 of draft-partain-..-00

   issues are:
   - occurs in a highly utilised network and  if it is not solved very
   fast then the network performance will  quickly collapse
   - deos it belong to failure recovery (I would assume from a service
   point of view this is failure
   - hop by hop problem (issue from Jorge)
   - What difference does it make (from the QoS perspective) if the
   provided QoS degraded due to hardware failure on a device or due to
   congestion caused by failures on some other devices? What is
   required from the protocol is to signal this failure to other
   participants (QCs or QI) in the hope that they can do something
   meaningful (e.g. re-routing) to correct the problem or tear down the
   flow.

   60) (CLOSED) add req 5.4.3. from draft-partain-...-00 "Allow
   efficient QoS re-establishment after handover"

   "Handover is an essential function in wireless networks. After
   handover, QoS may need to be completely or partially re-established
   due to route changes. The re-establishment may be requested by the
   mobile node itself or triggered by the access point that the mobile
   node is attached to.  In the first case, the QoS signalling should

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               Requirements for QoS Signaling Protocols       May 2002

   allow efficient QoS re-establishment after handover.  Re-
   establishment of QoS after handover should be as quick as possible
   so that the mobile node does not experience service interruption or
   QoS degradation. The re-establishment should be localized, and not
   require end-to-end signalling, if possible."

   - most likely it is already cover, please check again, whether there
   is something missing
   - added it again under the mobility requiremments

   61) (OPEN) add req: 6.1.8 from draft-bucheli-...-00 on multicast
   "Multicast consideration should not impact the protocol complexity
   for unicast flows. Multicast support is not considered as a
   priority, because the targeted interactive multimedia services are
   mainly unicast. For this reason, if considered in the solution,
   multicast should not bring complexity in the unicast scenario."

   Opinions?


   ---------------------------------------------------
   starting from -02 version
   ---------------------------------------------------

   62) (OPEN) Request to add VPN scenario
   - Related to issue 1)
   - Difference of VPN scenario compared to what we already have is
   missing

   63) (CLOSED) added Sven Van den Bosch, Maarten Buchli, and Danny
   Goderis to acknowledgement section.

   64) (OPEN) Request to add req: Backwards compatibility
   A later version of an NSIS protocol must be backwards compatible
   with earlier versions of an NSIS protocol.

   65) (OPEN) Request to add req: Unexpected situations and error
   restistance
   An NSIS protocol must define behaviour of NSIS signaling units
   during unexpected situations. Unexpected situtions are unknown
   messages, parameters and parameter settings as well as receiption of
   unexpected messages (e.g. a "Reservation Confirmation" without prior
   "Reservation Request").

   Related to Open issues (53) and requirement 5.3.4.
   This requirement is emphasizing to many details that might not be
   necessary

   Req 5.3.4 refers to behaviour in the case of problems in the data
   plane. My suggestion here is about unexpected events/errors in the
   control plane. If you think that this point carries to many details,
   let's split it up in several individual requirements.



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               Requirements for QoS Signaling Protocols       May 2002

   66) (OPEN) Request to add req: Default behaviour
   An NSIS protocol must define default behaviours and parameter
   settings wherever applicable.

   67) (OPEN) Request to add req: Extendability
   An NSIS protocol must provide means to enhance a protocol with
   future procedures, messages, parameters and parameter settings.

   This was refering mostly to the service specific part of the
   protocol.
   could be a part of the modularity requirement 5.1.3

   68) (OPEN) Request to add req: Preventation of stale state
   An NSIS signalling protocol must provide means for an NSIS signaling
   unit to discover and remove local stale state. This may for example
   be done by means like soft state and periodic flooding or by a
   polling mechanism and hard state signaling.

   Might already be covered in other requirements, could also be that
   the solutions known are solutions for different problems. I think
   distributed garbage collection could also be a solution.

   69) (OPEN) Request to add req: Reliable Communication
   NSIS signaling procedures, connectivity between units involved in
   NSIS signaling as well as the basic transport protocol used by NSIS
   must provide a maximum of communication reliability. Procedures must
   define how an NSIS signaling systems behaves if some kind of request
   it sent stays without answer (this could require e.g. be timers,
   number of message retransmits and release messages).
   An NSIS signaling unit must be able to check its connectivity to an
   adjacent NSIS signaling unit at any time (this requirement must
   however not result in a DoS attack tool - the frequency of these
   checks must be limited, and flow control may be useful).
   The basic transport protocol to be used between adjacent NSIS units
   must ensure message integrity and reliable transport.

   MUST/SHOULD ensure error- and loss free transmission of signaling
   information.

   Do we really require this? Isn't this a soft state versus hard state
   issue?

   70) (OPEN) Request to add req: Smooth breakdown
   A unit participating in NSIS signaling must no cause further damage
   to other systems involved in NSIS signaling when it has to go out of
   service.

   71) (CLOSED) Changed text "5.6.8: Ability to constrain load on
   devices" to

   The NSIS architecture should give the ability to constrain the load
   (CPU load, memory space, signaling bandwidth consumption and
   signaling intensity) on devices where it is needed. This can be
   achieved by many different methods. Examples, and this are only


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               Requirements for QoS Signaling Protocols       May 2002

   examples, include message aggregation, by ignoring signaling
   message, header compression, or minimizing functionality. The
   framework may choose any method as long as the requirement is met.

   72) (OPEN) request to add "Error notification and error location"

   "An NSIS signaling node rejecting or releasing a reservation must
   indicate its identity. NSIS signalling should indicate why a
   requested resource is not or no longer available. "

   Compared to 5.3.4 this is about problems on the control plane
   ------------------------------------------------------
   Change Log Version 01 -> 02
   - added issues 62-72

   - added some discussion text to open issues

   - req " highest possible network utilization" added (issue 33,
   closed)

   - issues closed: 34 (UMTS scenarios), 35 (PSTN gatway scenarios),

   - removed req "Avoid duplication of [sub]domain signaling
   functions", issue 51

   - Section 5.3.4: added explanation of recoverable and unrecoverable
   errors (issue 53)

   - added the following requirement: (closed issue 55) Allow local QoS
   information exchange between nodes of the saeme administrative
   domain

   The QoS signaling protocol must be able to exchange local QoS
   information between QoS controllers located within one single
   domain. Local QoS information might, for example, be IP addresses,
   severe congestion notification, notification of successful or
   erroneous processing of QoS signaling messages.
   In some cases, the NSIS QoS signalling protocol may carry
   identification of the QoS controllers located at the boundaries of a
   domain. However, the identification of edge should not be visible to
   the end host (QoS initiator) and only applies within one QoS
   administrative domain.

   - closed issue 57: add text about "Minimal impact on interior (core)
   nodes" to requirement 5.6.8 "Ability to constrain load on devices"

   - added requirement "Allow efficient QoS re-establishment after
   handover", closed issue 60.

   - changed text in 5.3.2





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