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Internet Engineering Task Force                               J. Manner
Internet-Draft                                                    X. Fu
Expires: June, 2005                                      December, 2004



        Analysis of Existing Quality of Service Signaling Protocols
               <draft-ietf-nsis-signalling-analysis-05.txt>



Status of this Memo

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   This Internet-Draft will expire in June, 2005.


Abstract

   This document reviews some of the existing QoS signaling protocols
   for an IP network. The goal here is to learn from them and to avoid
   common misconceptions. Further, we need to avoid the mistakes during
   the design and the implementation of any new protocol in this area.













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Table of Contents

   1 Background ...................................................    3
   2 RSVP and RSVP Extensions .....................................    4
   2.1 Basic Design ...............................................    4
   2.1.1 Signaling Model ..........................................    4
   2.1.2 Soft State ...............................................    5
   2.1.3 Two-pass Signaling Message Exchanges .....................    5
   2.1.4 Receiver-based Resource Reservation ......................    5
   2.1.5 Separation of QoS Signaling from Routing .................    5
   2.2 RSVP Extensions ............................................    6
   2.2.1 Simple Tunneling .........................................    6
   2.2.2 IPsec Interface ..........................................    6
   2.2.3 Policy Interface .........................................    6
   2.2.4 Refresh Reduction ........................................    7
   2.2.5 RSVP over RSVP ...........................................    7
   2.2.6 IEEE 802-style LAN Interface .............................    8
   2.2.7 ATM Interface ............................................    8
   2.2.8 DiffServ Interface .......................................    9
   2.2.9 Null Service Type ........................................    9
   2.2.10 MPLS Traffic Engineering ................................    9
   2.2.11 GMPLS and RSVP-TE .......................................   10
   2.2.12 GMPLS Operation at UNI and E-NNI Reference Points .......   11
   2.2.13 MPLS and GMPLS Future Extensions ........................   11
   2.2.14 ITU-T H.323 Interface ...................................   12
   2.2.15 3GPP Interface ..........................................   12
   2.3 Extensions For New Deployment Scenarios ....................   13
   2.4 Conclusion .................................................   14
   3 RSVP Transport Mechanism Issues ..............................   15
   3.1 Messaging Reliability ......................................   15
   3.2 Message Packing ............................................   15
   3.3 MTU Problem ................................................   16
   3.4 RSVP-TE vs. Signaling Protocol for RT Applications .........   16
   3.5 What will be a better alternative?  ........................   17
   4 RSVP Protocol Performance Issues .............................   17
   4.1 Processing Overhead ........................................   17
   4.2 Bandwidth Consumption ......................................   18
   5 RSVP Security and Mobility ...................................   19
   5.1 Security ...................................................   19
   5.2 Mobility Support ...........................................   19
   6 Other QoS Signaling Proposals ................................   20
   6.1 Tenet and ST-II ............................................   20
   6.2 YESSIR .....................................................   21
   6.2.1 Reservation Functionality ................................   21
   6.2.2 Conclusion ...............................................   22
   6.3 Boomerang ..................................................   22
   6.3.1 Reservation Functionality ................................   22
   6.3.2 Conclusions ..............................................   23
   6.4 INSIGNIA ...................................................   23
   7 Inter-domain Signaling .......................................   24
   7.1 BGRP .......................................................   24
   7.2 SICAP ......................................................   24
   7.3 DARIS ......................................................   25
   8 Security Considerations ......................................   27

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   9 IANA Considerations ..........................................   27
   10 Summary .....................................................   27
   11 Contributors ................................................   27
   12 Acknowledgment ..............................................   28
   13 Normative References ........................................   28
   14 Non-Normative References ....................................   28
   15 Authors' Information ........................................   32
   16  Appendix  A - Comparison of RSVP to the NSIS Requirements


1.  Background

   This document reviews some of the existing QoS signaling protocols
   for an IP network. The goal here is to learn from them and to avoid
   common misconceptions. Further, we need to avoid the mistakes during
   the design and the implementation of any new protocol in this area.

   There have been a number of historic attempts in delivering QoS or
   generic signaling into the Internet.  In the early years, multicast
   was believed to be going to be popular for the majority of
   communications, hence, both RSVP and earlier ST-II were designed in a
   way which is multicast-oriented.

   ST-II was developed as a reservation protocol for point-to-multipoint
   communication. However, since it is sender-initiated, it does not
   scale with the number of receivers in a multicast group. Its
   processing is fairly complex. Since every sender needs to set up its
   own reservation, the total amount of reservation states is large.
   RSVP was then designed to provide support for multipoint-to-
   multipoint reservation setup in a more efficient way, however its
   complexity, scalability and ability to meet new requirements have
   been criticized.

   YESSIR [PS98] and Boomerang [FNM+99] are examples of protocols
   designed after RSVP. Both protocols were meant to be simpler than
   RSVP. YESSIR is an extension to RTCP, while Boomerang is used with
   ICMP.

   Previously, there has been a lot of work targeted at creating a new
   signaling protocol for resource control. Istvan Cselenyi suggested to
   have a QoSSIG BOF in IETF47, for identifying problems in QoS
   signaling, but failed to get enough support [URL1]. Some people
   argued, "in many ways, RSVP improved upon ST-2, and it did start out
   simpler, but resulting a design with complexity and scalability",
   while some others thought it is "new knowledge and requirements" that
   made RSVP insufficient, and there is no simpler way to handle the
   same problem as RSVP.

   Michael Welzl organized a special session "ABR to the Internet" in
   SCI 2001, and gathered some inputs for requesting an "ABR to the
   Internet" BOF in IETF#51, which was intended to introduce explicit
   rate feedback related mechanisms for the Internet (e2e, edge2edge)
   but failed because of "missing community interest".


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   OPENSIG [URL2] has been involved in the Internet signaling for years.
   Ping Pan initiated a SIGLITE [URL3] BOF mailing list to investigate
   light-weight Internet signaling. Finally, NSIS BOF was successful and
   the NSIS WG was formed.

   The most mature and original protocols are presented in their own
   sections and other QoS signaling protocols are presented in later
   subsections. The presented protocols are chosen based on relevance to
   the work within NSIS. The aim is not to review every existing
   protocol.


2.  RSVP and RSVP Extensions

   RSVP (the Resource Reservation Protocol) [ZDSZ93] [RFC2205] [BEBH96]
   has evolved from ST-II to provide end-to-end QoS signaling services
   for application data streams. Hosts use RSVP to request a specific
   quality of service (QoS) from the network for particular application
   flows. Routers use RSVP to deliver QoS requests to all routers along
   the data path. RSVP also can maintain and refresh states for a
   requested QoS application flow.

   By original design, RSVP fits well into the framework of the
   Integrated Services (IntServ) [RFC2210] [BEBH96] with certain
   modularity and scalability.

   RSVP carries QoS signaling messages through the network, visiting
   each node along the data path. To make a resource reservation at a
   node, the RSVP module communicates with two local decision modules,
   admission control and policy control. Admission control determines
   whether the node has sufficient available resources to supply the
   requested QoS. Policy control provides authorization for the QoS
   request. If either check fails, the RSVP module returns an error
   notification to the application process that originated the request.
   If both checks succeed, the RSVP module sets parameters in a packet
   classifier and packet scheduler to obtain the desired QoS.


2.1.  Basic Design

   The design of RSVP distinguished itself by a number of fundamental
   ways, particularly, soft state management, two-pass signaling message
   exchanges, receiver-based resource reservation and separation of QoS
   signaling from routing.


2.1.1.  Signaling Model

   The RSVP signaling model is based on a special handling of multicast.
   The sender of a multicast flow advertises the traffic characteristics
   periodically to the receivers via "Path" messages. On receipt of an
   advertisement, a receiver may generate a "Resv" message to reserve
   resources along the flow path from the sender. Receiver reservations
   may be heterogeneous. To accommodate the multipoint-to-multipoint

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   multicast applications, RSVP was designed to support a vector of
   reservation attributes called the "style". A style describes whether
   all senders of a multicast group share a single reservation and which
   receiver is applied. The "Scope" object additionally provides the
   explicit list of senders.


2.1.2.  Soft State

   Because the number of receivers in a multicast flow is likely to
   change, and the flow of delivery paths might change during the life
   of an application flow, RSVP takes a soft-state approach in its
   design, creating and removing the protocol states (Path and Resv
   states) in routers and hosts incrementally over time. RSVP sends
   periodic refresh messages (Path and Resv) to maintain its states and
   to recover from occasional lost messages. In the absence of refresh
   messages, the RSVP states automatically time out and are deleted.
   States may also be deleted explicitly by PathTear, PathErr with
   Path_State_Removed flag, or ResvTear Message.


2.1.3.  Two-pass Signaling Message Exchanges

   The receiver in an application flow is responsible for requesting the
   desired QoS from the sender. To do this, the receiver issues an RSVP
   QoS request on behalf of the local application. The request
   propagates to all routers in reverse direction of the data paths
   toward the sender. In this process, RSVP requests might be merged,
   resulting in a protocol that scales well when there are a large
   number of receivers.


2.1.4.  Receiver-based Resource Reservation

   Receiver-initiation is critical for RSVP to setup multicast sessions
   with a large number of heterogeneous receivers. A receiver initiates
   a reservation request at a leaf of the multicast distribution tree,
   traveling toward the sender. Whenever a reservation is found to
   already exist in a node in the distribution tree, the new request
   will be merged with the existing reservation. This could result in
   fewer signaling operations for the RSVP nodes in the multicast tree
   close to the sender, but introduce a restriction to receiver-
   initiation.


2.1.5.  Separation of QoS Signaling from Routing

   RSVP messages follow normal IP routing. RSVP is not a routing
   protocol, but rather is designed to operate with current and future
   unicast and multicast routing protocols. The routing protocols are
   responsible for choosing the routes to use to forward packets, and
   RSVP consults local routing tables to obtain routes. RSVP is
   responsible only for reservation setup along a data path.


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   A number of messages and objects have been defined for the protocol.
   A detailed description is given in [RFC2205].


2.2.  RSVP Extensions

   RSVP [RFC2205] was originally designed to support real-time
   applications over the Internet. Over the past several years, the
   demand for multicast-capable real-time teleconferencing, which many
   people had envisioned to be one of the key Internet applications that
   could benefit from network-wide deployment of RSVP, has never
   materialized.  Instead, RSVP-TE [RFC3209], a RSVP extension for
   traffic engineering, has been widely deployed by a large number of
   network providers to support MPLS applications.

   There are a large number of protocol extensions based on RSVP. Some
   provide additional features, such as security and scalability, to the
   original protocol. Some introduce additional interfaces to other
   services, such as DiffServ. And some simply define new applications,
   such as MPLS and GMPLS, that are completely irrelevant from
   protocol's original intent.

   In this section, we list only IETF-based RFCs and a limited set of
   other organizations' specifications. Informational RFCs (e.g.,
   RFC2998 [RFC2998]) and work-in-progress I-Ds (e.g., proxy) are not
   covered here.


2.2.1.  Simple Tunneling

   [RFC2746] describes an IP tunneling enhancement mechanism that allows
   RSVP to make reservations across all IP-in-IP tunnels, basically, by
   way of recursively applying RSVP over the tunnel portion of the path.


2.2.2.  IPsec Interface

   RSVP can support IPsec on a per address, per protocol basis instead
   of on a per flow basis. [RFC2207] extends RSVP by using the IPsec
   Security Parameter Index (SPI) in place of the UDP/TCP-like ports.
   This introduces a new FILTER_SPEC object, which contains the IPsec
   SPI, and a new SESSION object.


2.2.3.  Policy Interface

   [RFC2750] specifies the format of POLICY_DATA objects and RSVP
   handling of policy events. It introduces objects which are
   interpreted only by policy aware nodes (PEPs) which interact with
   policy decision points (PDPs). Nodes which are unable to interpret
   the POLICY_DATA objects are called policy ignorant nodes (PINs). The
   content of the POLICY_DATA object itself is protected only between
   PEPs and therefore provides end-to-middle or middle-to-middle
   security.

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   [RFC2749] specifies the usage of COPS policy services in RSVP
   environments. [RFC3181] specifies a preemption priority policy
   element (PREEMPTION_PRI) for use by RSVP POLICY_DATA Object.
   [RFC3520] describes how authorization provided by a separate protocol
   (such as SIP) can be reused with the help of an authorization token
   within RSVP. The token might therefore contain either the authorized
   information itself (e.g. QoS parameters) or a reference to those
   values. The token might be unprotected (which is strongly
   discouraged) or protected based on symmetric or asymmetric
   cryptography. Moreover, the document describes how to provide the
   host with encoded session authorization information as a POLICY_DATA
   object.


2.2.4.  Refresh Reduction

   [RFC2961] describes mechanisms to reduce processing overhead
   requirements of refresh messages, eliminate the state synchronization
   latency incurred when an RSVP message is lost and, refreshing state
   without the transmission of whole refresh messages. It defines the
   following objects: MESSAGE_ID, MESSAGE_ID_ACK, MESSAGE_ID_NACK,
   MESSAGE_ID LIST, MESSAGE_ID SRC_LIST and MESSAGE_ID MCAST_LIST
   objects. Three new RSVP message types are defined:

   1) Bundle message, which consists of a bundle header followed by a
   body consisting one or more standard RSVP messages. Bundle messages
   help in scaling RSVP in reducing processing overhead and bandwidth
   consumption.

   2) ACK message, which carries one or more MESSAGE_ID_ACK or
   MESSAGE_ID_NACK objects. ACK messages are sent between neighboring
   RSVP nodes to detect message loss and support reliable RSVP message
   delivery on a per hop basis.

   3) Srefresh message, which carries one or more MESSAGE_ID LIST,
   MESSAGE_ID SRC_LIST and MESSAGE_ID MCAST_LIST objects. correspondent
   to Path and Resv messages that establish the states. Srefresh
   messages are used to refresh RSVP states without transmitting
   standard Path or Resv messages.


2.2.5.  RSVP over RSVP

   [RFC3175] allows to install one or more aggregated reservations in an
   aggregation region, thus the number of individual RSVP sessions can
   be reduced. The protocol type is swapped from RSVP to RSVP-E2E-IGNORE
   in E2E (standard) Path, PathTear and ResvConf messages when they
   enter the aggregation region, and swapped back when they leave. In
   addition to a new PathErr code (NEW_AGGREGATE_NEEDED), three new
   objects are introduced:

   1) SESSION object, which contains two values: the IP Address of the
   aggregate session destination, and the DSCP that it will use on the
   E2E data the reservation contains.

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   2) SENDER_TEMPLATE object, which identifies the aggregating router
   for the aggregate reservation.

   3) FILTER_SPEC object, which identifies the aggregating router for
   the aggregate reservation, and is syntactically identical to the
   SENDER_TEMPLATE object.

   From the perspective of RSVP signaling and the handling of data
   packets in the aggregation region, these cases are equivalent to the
   case of aggregating E2E RSVP reservations.  The only difference is
   that E2E RSVP signaling does not take place and cannot therefore be
   used as a trigger, so some additional knowledge is required in
   setting up the aggregate reservation.


2.2.6.  IEEE 802-style LAN Interface

   [RFC2814] introduces an RSVP LAN_NHOP address object that keeps track
   of the next L3 hop as the PATH message traverses an L2 domain between
   two L3 entities (RSVP PHOP and NHOP nodes). Both layer-2 and layer-3
   addresses are included in the LAN_NHOP; the RSVP_HOP_L2 object is
   used to include the Layer 2 address (L2ADDR) of the previous hop,
   complementing the L3 address information included in the RSVP_HOP
   object (RSVP_HOP_L3 address).

   To provide sufficient information for debugging or resource
   management, RSVP diagnostic messages (DREQ and DREP) are defined in
   [RFC2745] to collect and report RSVP state information along the path
   from a receiver to a specific sender.


2.2.7.  ATM Interface

   [RFC2379] and [RFC2380] define RSVP over ATM implementation
   guidelines and requirements to interwork with the ATM (Forum) UNI
   3.x/4.0.  [RFC2380] states that the RSVP (control) messages and RSVP
   associated data packets must not be sent on the same VCs, and an
   explicit release of RSVP associated QoS VCs must be performed once
   the VC for forwarding RSVP control messages terminates. While a
   separate control VC is also possible for forwarding RSVP control
   messages, [RFC2379] recommends to create a best-effort short-cut (a
   short-cut is a point-to-point VC where the two end-points locate in
   different IP subnets) first (if not exist), which can allow setting
   up RSVP triggered VCs to use the best-effort end-point. For data
   flows, the subnet senders must establish all QoS VCs and the RSVP
   enabled subnet receiver must be able to accept incoming QoS VCs. RSVP
   must request the configurable inactivity timers of VCs be set to
   "infinite", and if it is too complex to do this at the VC receiver,
   RSVP over ATM implementations are required not to use an inactivity
   timer to clear any received connections. In case of dynamic QoS, the
   replacement of VC should be done gracefully.




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2.2.8.  DiffServ Interface

   RFC2996 [RFC2996] introduces a DCLASS Object to carry Differentiated
   Services Code Points (DSCPs) in RSVP message objects. If the network
   element determines that the RSVP request is admissible to the
   DiffServ network, one or more DSCPs corresponding to the behavior
   aggregate are determined, and will be carried by the DCLASS Object
   added to the RESV message upstream toward the RSVP sender.


2.2.9.  Null Service Type

   For some applications, service parameters are specified by the
   network, not by the application, e.g., enterprise resource planning
   (ERP) applications. The Null Service [RFC2997] allows applications to
   identify themselves to network QoS policy agents using RSVP
   signaling, but does not require them to specify resource
   requirements. QoS policy agents in the network respond by applying
   QoS policies appropriate for the application (as determined by the
   network administrator). The RSVP sender offers the new service type,
   'Null Service Type' in the ADSPEC that is included with the PATH
   message. A new TSPEC corresponding to the new service type is added
   to the SENDER_TSPEC. In addition, the RSVP sender will typically
   include with the PATH message policy objects identifying the user,
   application and sub-flow, which will be used for network nodes to
   manage the correspondent traffic flow.


2.2.10.  MPLS Traffic Engineering

   RSVP-TE [RFC3209] specifies the core extensions to RSVP for
   establishing constraint-based explicitly routed LSPs in MPLS networks
   using RSVP as a signaling protocol. RSVP-TE is intended for use by
   label switching routers (as well as hosts) to establish and maintain
   LSP-tunnels and to reserve network resources for such LSP-tunnels.

   RFC3209 defines a new Hello message (for rapid node failure
   detection).

   RFC3209 also defines new C-Types (LSP_TUNNEL_IPv4 and
   LSP_TUNNEL_IPv6) for the SESSION, SENDER_TEMPLATE, and FILTER_SPEC
   objects. Here a session is the association of LSPs that support the
   LSP-tunnel. The traffic on an LSP can be classified as the set of
   packets that are assigned the same MPLS label value at the
   originating node of an LSP-tunnel.

   The following 5 new objects are also defined.

   1) EXPLICIT_ROUTE object (ERO), which is incorporated into RSVP Path
   messages, encapsulating a concatenation of hops which constitutes the
   explicitly routed path. Using this object, the paths taken by label-
   switched RSVP-MPLS flows can be pre-determined, independent of
   conventional IP routing.


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   2) LABEL_REQUEST object. To establish an LSP tunnel, the sender can
   create a Path message with a LABEL_REQUEST object. A node that sends
   a LABEL_REQUEST object MUST be ready to accept and correctly process
   a LABEL object in the corresponding Resv messages.

   3) LABEL object. Each node that receives a Resv message containing a
   LABEL object uses that label for outgoing traffic associated with
   this LSP tunnel.

   4) SESSION_ATTRIBUTE object, which can be added to Path messages to
   aid in session identification and diagnostics. Additional control
   information, such as setup and holding priorities, resource
   affinities and local-protection, are also included in this object.

   5) RECORD_ROUTE object (RRO). The RECORD_ROUTE object may appear in
   both Path and Resv messages. It is used to collect detailed path
   information and is useful for loop detection and for diagnostics.

   Section 5 of [RFC3270] further specifies the extensions to RSVP to
   establish LSPs supporting DiffServ in MPLS networks, introducing a
   new DIFFSERV Object (applicable in the Path messages) and using pre-
   configured or (e.g. RFC3270) signaled "EXP<-->PHB mapping".

   RSVP-TE provides a way to indicate an unnumbered link in its Explicit
   Route and Record Route Objects through [RFC3477]. This specifies the
   following extensions.

   - An Unnumbered Interface ID Subobject, which is a subobject of the
   Explicit Route Object (ERO) used to specify unnumbered links;

   - An LSP_TUNNEL_INTERFACE_ID Object, to allow the adjacent LSR to
   form or use an identifier for an unnumbered Forwarding Adjacency;

   - A new subobject of the Record Route Object, used to record that the
   LSP path traversed an unnumbered link.


2.2.11.  GMPLS and RSVP-TE

   GMPLS RSVP-TE [RFC3473] is an extension of RSVP-TE. It enables the
   provisioning of data-paths within networks supporting a variety of
   switching types including packet and cell switching networks, layer
   two networks, TDM networks and photonic networks.

   It defines the new Notify message (for general event notification),
   which may contain notifications being sent, with respect to each
   listed LSP, both upstream and downstream. Notify messages can be used
   for expedited notification of failures and other events to nodes
   responsible for restoring failed LSPs. A Notify message is sent
   without the router alert option.

   A number of new RSVP-TE (sub)objects are defined in GMPLS RSVP-TE for
   general uses of MPLS:


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   - a Generalized Label Request Object;
   - a Generalized Label Object;
   - a Suggested Label Object;
   - a Label Set Object; (to restrict label choice)
   - an Upstream_Label object; (to support bi-directional LSPs)
   - a Label ERO subobject;
   - IF_ID RSVP_HOP objects (IPv4 & IPv6; to identify interfaces in
     out of band signaling or in bundled links);
   - IF_ID ERROR_SPEC objects (IPv4 & IPv6; to identify interfaces in
     out of band signaling or in bundled links);
   - an Acceptable Label Set object (to support negotiation of label
     values in particular for bidirecitonal LSPs)
   - a Notify Request object (may be inserted in a Path or Resv message
     to indicate to where a notification of LSP failure is to be sent)
   - a Restart_Cap Object (used on Hello messages to identify recovery
     capabilities)
   - an Admin Status Object (to notify each node along the path of the
     status of the LSP, and to control that state).


2.2.12.  GMPLS Operation at UNI and E-NNI Reference Points

   The ITU-T defines network reference points that separate
   administrative or operational parts of the network. The reference
   points are designated as:

   - User to Network Interfaces (UNIs) if they lie between the user
     or user network and the core network.
   - External Network to Network Interfaces (E-NNIs) if they lie
     between peer networks, network domains, or subnetworks.

   GMPLS is applicable to the UNI and E-NNI without further
   modification, and no new messages, objects or C-Types are required.
   See [OVERLAY].


2.2.13.  MPLS and GMPLS Future Extensions

   At the time of writing MPLS and GMPLS are being extended by the MPLS
   and CCAMP Working Groups to support additional sophisticated
   functions. This will inevitably lead to the introduction of new C-
   Types for existing objects, and to the requirement for new objects
   (CNums). It is possible that new messages will also be introduced.

   Some of the key features and functions being introduced include:

   - Protection and restoration. Features will be developed to provide
      - end-to-end protection
      - segment protection
      - various protection schemes (1+1, 1:1, 1:n)
      - support of extra traffic on backup LSPs
   - Diverse path establishment for protection and load sharing
   - Establishment of point-to-multipoint paths
   - Inter-area and inter-AS path establishment

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      - with explicit path control
      - with bandwidth reservation
      - with path diversity
   - Support for the requirements of ASON signaling as defined by the
     ITU-T, including call and connection separation
   - Crankback during LSP setup.


2.2.14.  ITU-T H.323 Interface

   ITU-T H.323 ([H.323]) recommends the IntServ resource reservation
   procedure using RSVP. The information whether an endpoint supports
   RSVP should be conveyed during the H.245 [H.245] capability exchange
   phase, by setting appropriate qOSMode fields. If both endpoints are
   RSVP-capable, when opening an H.245 logical channel, a receiver port
   ID should be conveyed to the sender by the openLogicalChannelAck
   message.  Only after that, can a "Path - Resv - ResvConf" process
   take place. The timer of waiting for ResvConf message will be set by
   the endpoint. The action in case of this timer expires, as well as
   RSVP reservation fails in any point during an H.323 call, is up to
   the vendor to take. Once a ResvConf message is sent or received, the
   endpoints should stop reservation timers and resume with the H.323
   call procedures. Only explicit release of reservations are supported
   in [H.323]: before sending a closeLogicalChannel message for a
   stream, a sender should send a PathTear message if an RSVP session
   has been previous created for that stream; after receiving a
   closeLogicalChannel, a receiver should send a ResvTear similarly.
   Only the FF style is supported, even for point-to-multipoint calls.


2.2.15.  3GPP Interface

   3GPP TS 23.207 ([3GPP-TS23207]) specifies the QoS signaling procedure
   with policy control within the UMTS end-to-end QoS architecture. When
   using RSVP, the signaling source and/or destination are the User
   Equipments (UEs, devices that allow users access to network services)
   that locate in the Mobile Originating (MO) side and the Mobile
   Terminating (MT) side, and an RSVP signaling process can either
   trigger or be triggered by the (COPS) PDP Context
   establishment/modification process. The operation of refreshing
   states is not specified in [3GPP-TS23207]. If a bidirectional
   reservation is needed, the RSVP signaling exchange must be performed
   twice between the end-points. The authorization token and flow
   identifier(s) in a policy data object should be included in the RSVP
   messages sent by the UE, if the token is available in the UE. When
   both RSVP and Service-based Local Policy are used, the Gateway GPRS
   Support Node (GGSN, the access point of the network) should use the
   policy information to decide whether to accept and forward Path/Resv
   messages.






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2.3.  Extensions For New Deployment Scenarios

   As a well-acknowledged protocol in the Internet, RSVP is being more
   and more expected to provide a more generic service for various
   signaling applications. However, RSVP messages were designed in a way
   to optimally support end-to-end QoS signaling. To meet with the
   increasing demand for a signaling protocol to also operate in host-
   to-edge and edge-to-edge ways, and serve for some other signaling
   purposes in addition to end-to-end QoS signaling, RSVP needs to be
   developed more flexible and applicable for more generic signaling.

   RSVP proxies [BEGD02] extends RSVP by being able to originate or
   receive the RSVP message on behalf of the end node(s), so that
   applications may still benefit from reservations that are not truly
   end-to-end. However, there are certainly scenarios where an
   application would want to explicitly convey its non-QoS purposed (as
   well as QoS) data from a host into the network, or from an ingress
   node to an egress node of an administrative domain, but it must do so
   without burdening the network with excess messaging overhead. Typical
   examples are an end host desiring a firewall service from its
   provider's network and MPLS label setup within an MPLS domain.

   RSVP requires support from network routers and user space
   applications. Domains not supporting RSVP are traversed
   transparently. Unfortunately, like other IP options, RSVP messages
   implemented by way of IP alert option may result in themselves being
   dropped by some routers [FJ02].  Although applications need to be
   built with RSVP libraries, one article presents a mechanism that
   would allow any host to benefit from RSVP mechanisms without
   applications awareness [MHS02].

   A somewhat similar deployment benefit can be gained from the
   Localized RSVP (LRSVP) [JR03] [MSK+04]. The documents present the
   concept of local RSVP-based reservation that can be used to trigger
   reservation within an access network alone. In those cases, an end-
   host may request QoS from its own access network without the co-
   operation of a correspondent node outside the access network - this
   would be especially helpful when the correspondent node is unaware of
   RSVP. A proxy node responds to the messages sent by the end host and
   enables both upstream and downstream reservations. Furthermore, the
   scheme allows for faster reservation repairs following a handover by
   triggering the proxy to assist in an RSVP local repair.

   Still, in end-hosts which are low in processing power and
   functionality, having an RSVP daemon running and taking care of the
   signaling may introduce unnecessary overhead. One article [Kars01]
   proposes to create a remote API so that the daemon would in fact be
   running on the end-host's default router and the end-host application
   would send its requests to that daemon.

   Another potential problem lies in the limited sized of signaled data
   due to the limitation of message size. RSVP message must fit entirely
   into a single non-fragmented IP datagram. Bundle messages [RFC2961]
   can aggregate multiple RSVP messages within a single PDU, but still

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   only occupy one IP datagram (i.e., approximately 64K); if it exceeds
   the MTU, the datagram is fragmented by IP and reassembled at the
   recipient node.


2.4.  Conclusion

   A good signaling protocol should be transparent to the applications.
   RSVP has proven to be a very well designed protocol. However, it has
   a number of fundamental protocol design issues that requires more
   careful re-evaluation.

   The design of RSVP was originally targeted at multicast applications.
   The result has been that the message processing within nodes is
   somewhat heavy, mainly due to flow merging. Still, merging rules
   should not appear in the specification as they are QoS-specific.

   RSVP has a comprehensive set of filtering rules (WF, FF, shared) and
   is not tied to certain QoS objects (RSVP is not tied to IntServ GS/CL
   specifications). Objects were designed to be modular, but Xspecs
   (TSPEC, etc) are more or less QoS-specific and should be more
   generalized; there is no clear layering/separation between the
   signaled data and signaling protocol.

   RSVP uses a soft state mechanism to maintain states and allows each
   node to define its own refresh timer. The protocol is also
   independent of underlying routing protocols. Still, in mobile
   networks the movement of the mobile nodes may not properly trigger a
   reservation refresh for the new path and therefore a mobile node may
   be left without a reservation up to the length of the refresh timer.
   Furthermore, RSVP does not work properly with changing end-point
   identifiers, that is, if one of the IP addresses of a mobile node
   changes, the filters may not be able to identify the flow that had a
   reservation.

   From the security point of view, RSVP does provide the basic building
   blocks for deploying the protocol in various environments to protect
   its messages from forgery and modification. Hop-by-hop protection is
   provided. However, current RSVP security mechanism does not provide
   non-repudiation and protection against message deletion; the two-way
   peer authentication and key management procedures are still missing.

   Finally, since the publication of the RSVP standard, tens of
   extensions have emerged that allow for much wider deployment than
   RSVP was originally designed for, as for instance, the Subnet
   Bandwidth Manager, the NULL service type, aggregation, operation over
   tunneling and MPLS as well as diagnostic messages.

   Domains not supporting RSVP are traversed transparently by default.
   Unfortunately, like other IP options, RSVP messages implemented by
   way of IP alert option may result in themselves being dropped by some
   routers. Also, the maximal size of RSVP message is limited.

   The transport mechanisms, performance, security and mobility issues

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   are detailed in the following sections.


3.  RSVP Transport Mechanism Issues

3.1.  Messaging Reliability

   RSVP messages are defined as a new IP protocol (that is, a new ptype
   in the IP header). RSVP Path messages must be delivered end-to-end.
   In order for the transit routers to intercept the Path messages, a
   new IP Router Alert option [RFC2113] was introduced. This design is
   simple to implement and efficient to run. As shown from the
   experiments in [PS00], IP option processing introduces very little
   overhead on a Free BSD box with minor kernel changes.

   However, RSVP does not have a good message delivery mechanism.  If a
   message is lost on the wire, the next re-transmit cycle by the
   network would be one soft-state refresh interval later.  By default,
   a soft-state refresh interval is 30 seconds.

   To overcome this problem, [PS97] introduced a staged refresh timer
   mechanism, which has been defined as a RSVP extension in [RFC2961].
   The staged refresh timer mechanism retransmits RSVP messages until
   the receiving node acknowledges. It can address the reliability
   problem in RSVP.

   However, during its implementation, a lot of effort had to be spent
   on per-session timer maintenance, message retransmission (e.g., avoid
   message bursts) and message sequencing. In addition, we have to make
   an effort to try to separate the transport functions from protocol
   processing. For example, if a protocol extension requires a natural
   RSVP session time-out (such as RSVP-TE one-to-one fast-reroute [FAST-
   REROUTE]), we have to turn off the staged refresh timers.


3.2.  Message Packing

   According to RSVP [RFC2205], each RSVP message can only contain
   information for one session. In a network that has a reasonably large
   number of RSVP sessions, this constraint imposes a heavy processing
   burden on the routers. Many router OS is based on UNIX. [PS00] showed
   that the UNIX socket I/O processing is not very sensitive to packet
   size. In fact, processing small packets takes almost as much CPU
   overhead as processing large ones. However, processing too many
   individual messages can easily cause congestion at socket I/O
   interfaces.

   To overcome this problem, RFC2961 introduced the message bundling
   mechanism.  The bundling mechanism packs multiple RSVP messages
   between two adjacent nodes into a single packet. In one deployed
   router platform, the bundling mechanism has improved the number of
   RSVP sessions that a router can handle from 2,000 to over 7,000.



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3.3.  MTU Problem

   RSVP does not support message fragmentation and reassembly at
   protocol level.  If the size of a RSVP message is larger than the
   link MTU, the message will be fragmented. And the routers simply
   cannot detect and process RSVP message fragments.

   There is no solution for the MTU problem. Fortunately, at places
   where RSVP-TE has been used, either the amount of per-session RSVP
   data is never too large, or the link MTU is adjustable - PPP and
   Frame Relay can always increase or decrease the MTU sizes. For
   example, on some routers, a Frame Relay interface can support the
   link MTU size up to 9600 bytes.  Currently, the RSVP MTU problem is
   not a realistic concern in MPLS networks.

   However, when and if RSVP is used for end-user applications, where
   network security is an essential and critical concern, it is possible
   that the size of RSVP messages can be larger than the link MTU. It is
   important to notice that end-users are most likely to have to deal
   with a small 1500-byte Ethernet MTU.


3.4.  RSVP-TE vs. Signaling Protocol for RT Applications

   RSVP-TE works in an environment that is different from what the
   original RSVP has been designed for: in MPLS networks, the RSVP
   sessions that are used to support Label-Switched-Paths (LSP's) do not
   change frequently.

   In fact, the network operators typically set up the MPLS LSP's in
   such a way that they cannot switch too quickly. For example, the
   operators often regulate the CSPF (Constraint-based Shortest Path
   First, a routing algorithm operates from the network edge to compute
   the "most" optimal routes for the LSP's) computation interval to
   prevent or delay large volume of user traffic to shift from one
   session to the other during LSP path optimization. As a result, RSVP-
   TE does not have to handle a large amount of "triggered" (new or
   modified)  messages. Most of the messages are refresh messages, which
   can be handled by the mechanisms introduced in RFC2961. In
   particular, in the Summary Refresh extension [RFC2961], each RSVP
   refresh message can be represented as a 4-byte ID. The routers can
   simply exchange the ID's to refresh RSVP sessions. With the full
   implementation of RFC2961, MPLS routers do not have any RSVP scaling
   issue. On one deployed router platform, it can support over 50,000
   RSVP sessions in a stable backbone network.

   On the other hand, in many of the new applications where a signaling
   protocol is required, the user session duration can be relatively
   short.  The dynamics of adding/dropping user sessions could introduce
   a large number of "triggered" messages in the network. This can
   clearly introduce a substantial amount of processing overhead to the
   routers. This is one area where a new signaling protocol may be
   needed to reduce the processing complexity in the resource
   reservation process.

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3.5.  What will be a better alternative?

   A good signaling protocol should be transparent to the applications.
   On the other hand, the design of a signaling protocol must take the
   intended and potential applications into consideration.

   With the addition of RFC2961, RSVP-TE is sufficient to support its
   intended application, MPLS, within the backbone. There is no
   significant transport-layer problem that needs to be solved.

   In the last several years, a number of new applications have emerged
   that are proposed to need IP signaling, beyond the traditional ones
   associated with quality of service and resource allocation. On-path
   firewall control/nat traversal (synergistic with the midcom design of
   [RFC3303]) is one of these. There are far-out applications such as
   depositing active network code in network devices. Next-generation
   signaling protocols dealing with novel applications, with network
   security requirements, and with the MTU problems described above,
   will prevent the re-use of the existing RSVP transport mechanism.


   If a new transport protocol is needed, the protocol must be able to
   handle the following:

   - reliable messaging;

   - message packing;

   - the MTU problem;

   - small triggered message volume.


4.  RSVP Protocol Performance Issues

4.1.  Processing Overhead

   By processing overhead we mean the amount of processing required to
   handle messages belonging to a reservation session. This is the
   processing required in addition to the processing needed for routing
   an (ordinary) IP packet. The processing overhead of RSVP originates
   from two major issues:

   1) Complexity of the protocol elements. First, RSVP itself is
     per-flow based, thus the number of states is proportional to RSVP
     session number. Path and Resv states have to be maintained in each
     RSVP router for each session (and Path state also record the
     reverse route for the correspondent Resv message). Second, being
     receiver-initiated, RSVP optimizes various merging operations for
     multicast reservations while the Resv message is processed. To
     handle multicast, other mechanisms like reservation styles, scope
     object, and blockade state, are also required to present in the
     basic protocol. This not only adds sources of failures and errors,
     but also complicates the state machine [Fu02]. Third, the same RSVP

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     signaling messages are not only used for maintaining the state, but
     also dealing with recovery of signaling message loss and discovery
     of route change.  Thus, although protocol elements that represent
     the actual data (e.g., QoS parameters) specification are separated
     from signaling elements, the processing overhead needed for all
     RSVP messages is not marginal.  Finally, the possible variations of
     the order and existence of objects increases the complexity of
     message parsing and internal message and state representation.

   2) Implementation-specific Overhead. There are two ways to send and
     receive RSVP messages, either as "raw" IP datagrams with protocol
     number 46, or as encapsulated UDP datagrams, the latter of which
     increase the efficiency of RSVP processing. Typical RSVP
     implementations are user-space daemons interacting with the
     kernel, hence state management, message sending and reception
     would affect the efficiency of the protocol processing.  For
     example, in the recent version of the implementation described in
     [KSS01], the relative execution costs for message
     sending/reception system calls "sendto", "select", "recvmsg" were
     14-16%, 6-7%, 9-10%, individually, of the total execution cost;
     [KSS01] also found that state (memory) management can use up to
     17-18% of the total execution cost, but it is possible to decrease
     that cost to 6-7%, if appropriate action is taken to replace the
     standard memory management with dedicated memory management for
     state information.  RSVP/routing, RSVP/policy control, and
     RSVP/traffic control interfaces can also pose different overhead
     dependent on implementation. For example, the RSVP/routing
     overhead has been measured to be approximately 11-12% of the total
     execution cost [KSS01].


4.2.  Bandwidth Consumption

   By bandwidth consumption we mean the amount of bandwidth used to
   during the lifetime of a session: set up a reservation session, keep
   the session alive, and finally close it.

   RSVP messages are sent either to trigger a new reservation or refresh
   an existing reservation. In standard RSVP, Path/Resv messages are
   used for triggering and refreshing/recovering reservations,
   identically, which results in an increased size of refresh messages.
   The hop-by-hop refreshment may reduce the bandwidth consumption for
   RSVP, but could result in more sources of error/failure events.
   [RFC2961] presents a way to bundle standard RSVP messages and reduces
   the refreshment redundancy by Srefresh message.

   Thus, the signaling for an RSVP session uses for a session lasting n
   seconds:

   F(n) = (bP + bR) + ((n/Ri) * (bP + bR)) + bPt ,where

   bP IP payload size of Path message
   bR IP payload size of Resv message
   bPt IP payload size of Path Tear message

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   Ri refresh interval

   For example, for a simple Controlled Load reservation without
   security and identification requirements the bandwidth consumption
   would be (bP is 172 bytes, bR is 92, and bPt is 44 bytes and Ri is 30
   seconds):

   F(n): (172 + 92) + (n/30) * (172 + 92)) + 44 =  308 + (264n/30) bytes


5.  RSVP Security and Mobility

5.1.  Security

   To allow a process on a system to securely identify the owner and the
   application of the communicating process (e.g. user id) and convey
   this information in RSVP messages (PATH or RESV) in a secure manner,
   [RFC3182] specifies the encoding of identities as RSVP POLICY_DATA
   Object. However, to provide iron-clad security protection
   cryptographic authentication combined with authorization has to be
   provided. Such a functionality is typically offered by authentication
   and key exchange protocols. Solely including a user identifier is
   insufficient.

   To provide hop-by-hop integrity and authentication of RSVP messages,
   RSVP message may contain an INTEGRITY object ([RFC2747]) using a
   keyed message digest. Since intermediate routers need to modify and
   process the content of the signaling message a hop-by-hop security
   architecture based on a chain-of-trust is used. However, with the
   different usage of RSVP as described throughout this document and
   with new requirements a re-evaluation of the original assumptions
   might be necessary.

   RFC2747 provides protection against forgery and message modification.
   However this does not provide non-repudiation and protect against
   message deletion. In current RSVP security scheme, the two-way peer
   authentication and key management procedures are still missing.

   The security issues have been well analyzed in [Tsch03].


5.2.  Mobility Support

   Two issues raise concern when RSVP is used by a mobile node (MN): the
   flow identifier and reservation refresh. When an MN changes
   locations, it may need to change one of its assigned IP address. An
   MN may have an IP address by which it is reachable by nodes outside
   the access network and an IP address used to support local mobility
   management. Depending on the mobility management mechanism, a
   handover may force a change in any of these addresses. As a
   consequence the filters associated with a reservation may not
   identify the flow anymore and the resource reservation is
   ineffective, until a refresh with a new set of filters is
   initialized.

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   The second issue is about following the movement of a mobile node.
   RFC2205 defines that Path messages can perform a local repair of
   reservation paths. When the route between the communicating end hosts
   changes, a Path message will set the state of the reservation on the
   new route and a subsequent Resv message will make the resource
   reservation. Therefore, by sending a Resv message a host cannot alone
   update the reservation, and thus perform a local repair, before a
   Path message has passed. Also, in order to provide fast adaptation to
   routing changes without the overhead of short refresh periods, the
   local routing protocol module can notify the RSVP process of route
   changes for particular destinations. The RSVP process should use this
   information to trigger a quick refresh of state for these
   destinations, using the new route (Chapter 3.6, RFC2205). However,
   not all local mobility protocols, or even Mobile IP, affect routing
   directly in routers, and thus mobility may not be noticed at RSVP
   routers. Thus, it may take a relatively long time before a
   reservation is refreshed following a handover.

   There have been several designs for extensions to RSVP to allow for
   more seamless mobility. One solution is presented in [MSK+04], which
   discusses in one section the coupling of RSVP and the mobility
   management mechanisms and proposes small extensions to RSVP to better
   handle the handover event, among other things. The extension allows
   the mobile host to request a Path for the downstream reservation when
   a handover has happened.

   Another example is Mobile RSVP (MRSVP) [TBA01], which is an extension
   to standard RSVP. It is based on advance reservations, where
   neighboring access points keep resources reserved for mobile nodes
   moving to their coverage area. When a mobile node requests resources,
   the neighboring access points are checked too and a passive
   reservation is done around the mobile nodes current location.

   The problem with the various 'advance reservation' schemes is that
   they require topological information of the access network and
   usually advance knowledge of the handover event. Furthermore, the way
   the resource reserved in advance are used in the neighboring service
   areas is an open issue. A good overview of these different schemes
   can be found in [MA01].

   The interactions of RSVP and Mobile IP have been well documented in
   [Thom02].


6.  Other QoS Signaling Proposals

6.1.  Tenet and ST-II

   Tenet and ST-II are two original QoS signaling protocols for the
   Internet.

   In the original Tenet architecture [BFM+96], the receiver sends a
   reservation request toward the source.  Each network node along the
   way makes the reservation. Upon arriving at the source, the source

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   sends another Relax message back toward to the receiver, and has the
   option to modify the previous reservation at each node.

   ST-II [RFC1819] basically works as the following: a sender originates
   a Connect message to a set of receivers. Each intermediate node
   determines the next hop subnets, and makes reservations on the links
   going to these next hops.  Upon receiving a Connect indication, a
   receiver must send back either an Accept or a Refuse message to the
   sender.  In the case of an Accept, the receiver may further reduce
   the resource request by updating the returned flow specifications.

   ST-II consists of two protocols: ST for the data transport and SCMP,
   the Stream Control Message Protocol, for all control functions.  ST
   is simple and contains only a single PDU format that is designed for
   fast and efficient data forwarding in order to achieve low
   communication delays. SCMP packets are transferred within ST packets.

   ST-II has no built-in soft states, thus requires that the network be
   responsible for correctness. It is sender-initiated, and the overhead
   for ST-II to handle group membership dynamics is higher than RSVP
   [MESZ94].  ST-II does not provide security but RFC 1819 describes
   some objects related to charging.


6.2.  YESSIR

   YESSIR (YEt another Sender Session Internet Reservations) [PS98] is a
   resource reservation protocol that seeks to simplify the process of
   establishing reserved flows while preserving many unique features
   introduced in RSVP. Simplicity is measured in terms of control
   message processing, data packet processing, and user-level
   flexibility. Features such as robustness, advertising network service
   availability and resource sharing among multiple senders are also
   supported in the proposal.

   The proposed mechanism generates reservation requests by senders to
   reduce the processing overhead. It is built as an extension to the
   Real-Time Transport Control Protocol (RTCP), taking advantages of
   Real-Time Protocol (RTP). YESSIR also introduces a concept called
   partial reservation, where, for certain types of applications, the
   reservation requests can be passed to the next hop, even though there
   is not enough resources on a local node. The local node can rely on
   optimized retries to complete the reservations.


6.2.1.  Reservation Functionality

   YESSIR [PS98] was designed for one-way, sender-initiated end-to-end
   resource reservation. It also uses soft state to maintain states. It
   supports resource query (similar to RSVP diagnosis message),
   advertising (similar to RSVP ADSPEC), shared reservation, partial
   reservations and flow merging.

   To support multicast, YESSIR simplifies the reservation styles to

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   individual and shared reservation styles. Individual reservations are
   made separately for each sender, whereas shared reservations allocate
   resources that can be used by all senders in an RTP session. While
   RSVP supports shared reservation (SE and WF styles) from the
   receiver's direction, YESSIR handles the shared reservation style
   from the sender's direction, thus new receivers can re-use the
   existing reservation of the previous sender.

   It has been shown that the YESSIR one-pass reservation model has
   better performance and lower processing cost, comparing with a
   regular two-way signaling protocol, such as RSVP [PS98]. The
   bandwidth consumption of YESSIR is somewhat lower than that of, for
   example, RSVP, because it does not require additional IP and
   transport headers. Bandwidth consumption is limited to the extension
   header size.

   YESSIR does not have any particular support for mobility and the
   security of YESSIR relies on RTP/RTCP security measures.


6.2.2.  Conclusion

   YESSIR requires support in applications since it is an integral part
   of RTCP. Similarly, it requires network routers to inspect RTCP
   packets to identify reservation requests and refreshes. Routers
   unaware of YESSIR forward the RTCP packets transparently.


6.3.  Boomerang

   Boomerang [FNM+99] is a another resource reservation protocol for IP
   networks. The protocol has only one message type and a single
   signaling loop for reservation set-up and tear-down, has no
   requirements on the far end node, but, instead, concentrates the
   intelligence in the Initiating Node (IN).

   In addition, the Boomerang protocol allows for sender- or receiver-
   oriented reservations and resource query. Flows are identified with
   the common 5-tuple and the QoS can be specified with various means,
   e.g.. service class and bit rate. Boomerang messages are in the
   initial implementation transported in ICMP ECHO / REPLY messages.


6.3.1.  Reservation Functionality

   Boomerang can only be used for unicast sessions, no support for
   multicast exists. The requested QoS can be specified with various
   methods and both ends of a communication session can make a
   reservation for their transmitted flow.

   The authors of Boomerang show in [FNS02] that the processing of the
   protocol is considerably lower than with the ISI RSVP daemon
   implementation. However, this is mainly due to the limited
   functionality provided by the protocol compared to RSVP.

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   Boomerang messages are quite short and consume a relatively low
   amount of link bandwidth. This is due to the limited functionality of
   the protocol, for example, no security specific information or
   policy-based interaction are provided. Being sender oriented, the
   bandwidth consumption mostly affects the downstream direction, from
   the sender to the receiver.

   As Boomerang is sender oriented, there is no need to store backward
   information. This reduces the signaling required. The rest of the
   issues that were identified with RSVP apply with Boomerang. No
   security mechanism is specified for Boomerang.

   The Boomerang protocol has similar deployment issues as any host-
   network-host protocol. It requires an implementation at both
   communicating nodes and in routers. Boomerang-unaware routers should
   be able to forward Boomerang messages transparently. Still, often
   firewalls drop ICMP packets making the protocol useless.


6.3.2.  Conclusions

   Boomerang seems to be a very lightweight protocol and efficient in
   its own scenarios. Still, the apparent low processing overhead and
   bandwidth consumption results from the limited functionality. No
   support for multicast or any security features are present which
   allows for a different functionality than RSVP, which the authors
   like to compare Boomerang to.


6.4.  INSIGNIA

   INSIGNIA [LGZC00] is proposed as a very simple signaling mechanism
   for supporting QoS in mobile ad-hoc networks. It avoids the need for
   separate signaling by carrying the QoS signaling data along with the
   normal data in IP packets using IP packet header options.  This
   approach, known as "in-band signaling" is proposed as more suitable
   in the rapidly changing environment of mobile networks since the
   signaled QoS information is not tied to a particular path.  It also
   allows the flows to be rapidly established and, thus, is suitable for
   short lived and dynamic flows.

   INSIGNIA aims to minimize signaling by reducing the number of
   parameters that are provided to the network. It assumes that real-
   time flows may tolerate some loss, but are very delay sensitive so
   that the only QoS information needed is the required minimum and
   maximum bandwidth.

   The INSIGNIA protocol operates at the network layer and assumes that
   link status sensing and access schemes are provided by lower layer
   entities. The usefulness of the scheme depends upon the MAC layers
   but this is undefined so that INSIGNIA can run over any MAC layer.
   The protocol requires that each router maintains per-flow state.

   The INSIGNIA system implicitly supports mobility. A near-minimal

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   amount of information is exchanged with the network. To achieve this,
   INSIGNIA makes many assumptions about the nature of traffic that a
   source will send. This may also simplify admission control and buffer
   allocation. The system basically assumes that "real-time" will be
   defined as a maximum delay and the user can simply request real-time
   service for a particular quantity of traffic.

   After handover, data that was transmitted to the old base station can
   be forwarded to the new base station so that no data loss should
   occur. However, there is no way to differentiate between re-routed
   and new traffic so priority cannot be given to handover traffic, for
   example.

   INSIGNIA, however, (completely) lacks a security framework and does
   not investigate how to secure signaled QoS data in ad-hoc network
   where relatively weak trust or even no trust exists between the
   participating nodes. Hence authorization and charging especially
   might be a challenge. The security protection of in-band signaling is
   costly since the data delivery itself experiences increased latency
   if security processing is done hop-by-hop. Since the QoS signaling
   information is encoded into the flow label and end-to-end addressing
   is used, it is very difficult to provide security other than IPsec in
   tunnel mode.


7.  Inter-domain Signaling

   This section gives a short overview of protocols designed for inter-
   domain signaling.


7.1.  BGRP

   Border Gateway Reservation Protocol (BGRP) [BGRP] is a signaling
   protocol for inter-domain aggregated resource reservation for unicast
   traffic. BGRP builds a sink tree for each of the stub domains.  Each
   sink tree aggregates bandwidth reservations from all data sources in
   the network. BGRP maintains these aggregated reservations using soft
   state and relies on Differentiated Services for data forwarding.

   BGRP scales in terms of message processing load, state storage and
   bandwidth.  Since backbone routers only maintain the sink tree
   information, the total number of reservations at each router scales
   linearly with the number of Internet domains.


7.2.  SICAP

   SICAP (Shared-segment Inter-domain Control Aggregation protocol)
   [SGV03] is an inter-domain signaling solution that performs shared-
   segment aggregation [SGV02] on the Autonomous System (AS) level with
   the purpose of reducing state required at Boundary Routers (BRs).
   SICAP performs aggregation based on path segments that different
   reservations share. Thus, reservations may be merged into aggregates

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   that do not extend necessarily all the way until the reservation's
   destination. The motivation for creating "shorter" aggregates is, on
   the one hand, their ability to more easily accommodate future
   requests, and on the other hand, the minimization of aggregates
   created and consequently, the reduction of state required to manage
   established reservations. However, and in contrast to the sink-tree
   approach (used by BGRP [BGRP]), the shared-segment approach
   introduces intermediate de-aggregation locations: these are ASes
   where aggregates may experience "re-aggregation". At these locations,
   routers that perform aggregation (AS egress routers) have to keep
   track of the mapping between reservations and aggregates. One
   possible way of doing this is to keep each reservation identifier and
   corresponding resources stored at each aggregator.  However, this
   solution incurs a high state penalty on state. SICAP avoids this
   state penalty by keeping track of the mapping between aggregates and
   reservations at the level of destination domains rather than
   explicitly mapping individual reservations to aggregates. In other
   words, SICAP maintains per aggregate a list of the destination
   prefixes advertised by the destination AS an aggregate provides
   access to.

   Pan et al. show that BGRP scales well in terms of control state,
   message processing, and bandwidth efficiency, when compared to RSVP
   without aggregation. However, and partially given that it was the
   first approach to explore in detail the issue of inter-domain control
   aggregation, they did not provide a comparison with other aggregation
   protocols.

   SICAP and BGRP messaging sequences are similar and consequently,
   these protocols attain the same signaling load. Such load is exactly
   the same attained by proposals that do not perform aggregation, given
   that SICAP and BGRP exchange messages per individual reservation. In
   terms of bandwidth, both protocols provision aggregates with the
   exact bandwidth required by their merged reservations. Therefore, the
   major difference between SICAP and BGRP is state maintained at BRs,
   which is significantly reduced by SICAP. We consider this to be of
   importance not so much to offer a better performing alternative to
   BGRP, but to quantify the performance improvements that might still
   be available in the research field of control path aggregation.
   Finally, to deal with the possible problem of the signaling load,
   SICAP uses an over-reservation mechanism[SGV03b], whose design took
   into consideration a possible support for BGRP.


7.3.  DARIS

   Dynamic Aggregation of Reservations for Internet Services (DARIS)
   [Bless02] [Bless04] defines an inter-domain aggregation scheme for
   resource reservations. Basically, it aggregates reservations along
   Autonomous System (AS) paths (or parts thereof). A set of
   reservations whose data paths share a common sequence of ASes are
   integrated into a joint reservation aggregate along that shared sub-
   path. All entities within the aggregate, except aggregate starting
   and end point, can remove state information of the included

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   individual reservations, thereby saving states. They just need to
   hold the necessary information about the encompassing aggregate.
   Moreover, these intermediate ASes are no longer involved in signaling
   that is related to the aggregated reservations. If more aggregate
   resources are reserved than were actually required, the capacity of
   the aggregate does not need to be adapted with every new or released
   reservation (thereby reducing the number of message exchanges).

   An aggregate between two ASes is created as soon as a threshold k is
   exceeded that describes the active number of unidirectional
   reservations between them. It is, however, possible to apply
   different aggregation triggers. Furthermore, DARIS allows to nest
   aggregates hierarchically. Therefore, the existence of shorter
   aggregates does not prevent the creation of longer (and thus more
   efficient) aggregates and vice versa. An evaluation of recent BGP
   routing information in [Bless02] showed that 92% of all end-to-end
   paths contain at least four ASes. Consequently, an aggregate from
   edge AS to edge AS can span four or more ASes, thus saving states and
   signaling message processing in at least two ASes.

   There is, however, a small chance that a reservation cannot be
   included into a new aggregate, because it was already aggregated
   elsewhere. This so-called "aggregation conflict" is caused by the
   fact that state information related to individual reservations was
   already removed within intermediate ASes of the encompassing
   aggregate. This may also bring difficulties in case that reservations
   or aggregates are re-routed between ASes. One must be careful when
   considering to define sophisticated adaptation techniques for these
   special cases, because they seem to become very complex.

   The signaling protocol DMSP (Domain Manager Signaling Protocol)
   supports aggregation by special extensions which reduce the
   reservation setup time for more than one round-trip time in some
   cases (e.g., if an aggregate's capacity must be increased before a
   new reservation can be included). Details can be found in [Bless02].

   The DARIS concept was evaluated by using a simulation with a topology
   that was derived from real BGP routing table information and
   comprised more than 5500 ASes. In comparison to a non-aggregated
   scenario the number of saved states lay in the range of one to two
   orders of magnitude and similar results were obtained with respect to
   the number of signaling messages. Though [Bless02] describes DARIS in
   the context of distributed Domain Management entities (similar to a
   bandwidth broker) it can be applied in a router-based resource
   management environment, too. This will achieve a higher degree of
   distribution which is beneficial for large ASes which are highly
   interconnected.

   A general issue with aggregation is that not the aggregating and de-
   aggregating ASes profit from their initiated aggregates, but all
   intermediate ASes within an aggregate. Therefore, some incentive for
   aggregate creation has to be given. This may lead to novel cost
   models that have to be developed for aggregation concepts in the
   future.

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8.  Security Considerations

   This document does not present new technology or protocols, thus,
   there are no explicit security issues. Still, individual protocols
   include different levels of security issues and those are highlighted
   in the relevant sections and references.


9.  IANA Considerations

   This draft presents and analyzes RSVP and other QoS signaling
   protocols.  No new protocol or technology is defined, thus, there are
   no actions for IANA.


10.  Summary

   Supporting flow-based soft state reservations has been proven useful.
   Still, there have been different ways of improving the performance,
   including refresh reduction and aggregation. However, some of the
   main concerns with these signaling protocols are the complexity of
   the protocol, which affects implementations and processing overhead,
   and the security of the signaling. Especially, a proper scheme to
   handle authentication, authorization of QoS resource requests and a
   framework for providing signaling message security seems to be
   missing from most protocols. RSVP has a mechanism to protect
   signaling messages based on manually distributed keys and concepts
   for authorization but they seem to be insufficient for a dynamic and
   mobile environment. [Tsch03] provides more details on security
   properties provided by RSVP. Moreover, secure and efficient signaling
   to and from mobile nodes has been one of the critical challenges not
   fully met by existing protocols.

   Moving QoS signaling protocols into a generic messenger can provide
   much adoption. It is expected that the development of future
   protocols should learn from the lessons of existing ones.
   Nevertheless, the tradeoffs between the expected functionality,
   protocol complexity/performance would still be taken into account.
   For example, RSVP uses the two-way signaling mechanism, where as
   YESSIR employs only one-pass signaling. Both can be shown to out-
   perform the other in specific carefully chosen signaling scenarios.


11.  Contributors

   This document is part of the work done in the NSIS Working Group. The
   draft was initially written by Jukka Manner and Xiaoming Fu. Since
   the first version, Martin Karsten has provided text about the
   processing overhead of RSVP and Hannes Tschofenig has provided text
   about various security issues in the protocols. Henning Schulzrinne
   and Ping Pan have provided more information on RSVP transportation
   after the second revision. Kireeti Kompella and Adrian Farrel
   provided a review and updates to the discussion on RSVP-TE and GMPLS.


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12.  Acknowledgment

   We would like to acknowledge Bob Braden and Vlora Rexhepi for their
   useful comments.


13.  Normative References

   [RFC3726] M. Brunner, "Requirements for Signaling Protocols", RFC
   3726, April 2004.


14.  Non-Normative References

   [3GPP-TS23207] 3GPP TS 23.207 V5.6.0, End-to-end Quality of Service
   (QoS) Concept and Architecture, Release 5, Dec. 2002.

   [BEBH96] Braden, R., Estrin, D., Berson, S., Herzog, and D.  Zappala,
   "The Design of the RSVP Protocol", ISI Final Technical Report, Jul
   1996.

   [BEGD02] Y. Bernet, N. Elfassy, S. Gai, and D. Dutt, "RSVP Proxy",
   draft-ietf-rsvp-proxy-03 (work in progress), March 2002.

   [BFM+96] A. Banerjea, D. Ferrari, B. Mah, M. Moran, D. Verma, and H.
   Zhang, "The Tenet Real-Time Protocol Suite: Design, Implementation,
   and Experiences", IEEE/ACM Transactions on Networking, Volume 4,
   Issue 1, February 1996, pp. 1-10.

   [BGP4] Y. Rekhter, T. Li, and S. Hares, "A Border Gateway Protocol 4
   (BGP-4)", Internet Draft, Work in Progress, November 2003 (draft-
   ietf-idr-bgp4-23.txt).

   [BGRP] P. Pan, E, Hahne, and H. Schulzrinne, "BGRP: A Tree-Based
   Aggregation Protocol for Inter-domain Reservations", Journal of
   Communications and Networks, Vol. 2, No. 2, June 2000, pp. 157-167.

   [Bless02] R. Bless, "Dynamic Aggregation of Reservations for Internet
   Services", Proceedings of the Tenth International Conference on
   Telecommunication Systems - Modeling and Analysis (ICTSM 10), Vol. 1,
   pp. 26-38, October 3-6 2002, Monterey California, slightly revised
   version available under http://www.tm.uka.de/doc/2003/ictsm-daris-
   journal-crc-web.pdf

   [Bless04] R. Bless, "Towards Scalable Management of QoS-based End-to-
   End Services" (PDF), Proceedings of NOMS 2004 (IEEE/IFIP 2004 Network
   Operations and Management Symposium), April 2004, Seoul, Korea.

   [FAST-REROUTE] P. Pan, G. Swallow, and A. Atlas, "Fast Reroute
   Extensions to RSVP-TE for LSP Tunnels", Internet Draft, Work in
   Progress, January 2004 (draft-ietf-mpls-rsvp-lsp-fastreroute-01.txt).

   [FNM+99] G. Feher, K. Nemeth, M. Maliosz, I. Cselenyi, J.  Bergkvist,
   D. Ahlard, T. Engborg, "Boomerang A Simple Protocol for Resource

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   Reservation in IP Networks", IEEE RTAS, 1999.

   [FNS02] G. Feher, K. Nemeth, and I. Cselenyi, "Performance evaluation
   framework for IP resource reservation signalling". Performance
   Evaluation 48 (2002), pp. 131-156.

   [FJ02] P. Fransson and A. Jonsson, "The need for an alternative to
   IPv4-options", in RVK (RadioVetenskap och Kommunikation), Stockholm,
   Sweden, pp. 162-166, June 2002.

   [Fu02] X. Fu, C. Kappler, and H. Tschofenig, "Analysis on RSVP
   Regarding Multicast". Technical Report No. IFI-TB-2002-001, ISSN
   1611-1044, Institute for Informatics, University of Goettingen, Oct
   2002.

   [H.245] ITU-T Recommendation H.245, Control Protocol for Multimedia
   Communication, July 2000.

   [H.323] ITU-T Recommendation H.323, Packet-based Multimedia
   Communications Systems, Nov. 2000.

   [JR03] Jukka Manner, Kimmo Raatikainen, "Localized QoS Management for
   Multimedia Applications in Wireless Access Networks". IASTED
   International Conference on Internet and Multimedia Systems and
   Applications (IMSA 2003), August, 2003, pp. 193 - 200.

   [Kars01] M. Karsten, "Experimental Extensions to RSVP -- Remote
   Client and One-Pass Signalling". IWQoS 2001, Karlsruhe, Germany, June
   2001.

   [KSS01] M. Karsten, Jens Schmitt, Ralf Steinmetz, "Implementation and
   Evaluation of the KOM RSVP Engine". IEEE Infocom 2001.

   [LGZC00] S. Lee, A. Gahng-Seop, X. Zhang, A. Campbell,"INSIGNIA: An
   IP-Based Quality of Service Framework for Mobile Ad Hoc Networks".
   Journal of Parallel and Distributed Computing (Academic Press),
   Special issue on Wireless and Mobile Computing and Communications,
   Vol. 60, Number 4, April, 2000, pp. 374-406.

   [MA01] B. Moon, and H. Aghvami, "RSVP Extensions for Real-Time
   Services in Wireless Mobile Networks". IEEE Communications Magazine,
   December 2001, pp. 52-59.

   [MESZ94] D. Mitzel, D. Estrin, S. Shenker, and L. Zhang, "An
   Architectural Comparison of ST-II and RSVP", INFOCOM'94.

   [MHS02] Y Miao, W. Hwang, and C. Shieh, "A transparent deployment
   method of RSVP-aware applications on UNIX". Computer Networks, 40
   (2002), pp.  45-56.

   [MSK+04] J. Manner, T. Suihko, M. Kojo, M. Liljeberg, K. Raatikainen,
   "Localized RSVP". Internet Draft, Work in Progress, September 2004
   (draft-manner-lrsvp-04.txt).


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   [OVERLAY] G. Swallow, J. Drake, H. Ishimatsu, and Y. Rekhter, "GMPLS
   UNI: RSVP Support for the Overlay Model", Internet Draft, work in
   progress, February 2004 (draft-ietf-ccamp-gmpls-overlay- 03.txt).

   [PS97] P. Pan, and H. Schulzrinne, "Staged refresh timers for RSVP",
   Global Internet, Phoenix, Arizona, Nov. 1997.

   [PS98] P. Pan, and H. Schulzrinne, "YESSIR: A Simple Reservation
   Mechanism for the Internet". Proceedings of NOSSDAV, Cambridge, UK,
   July 1998.

   [PS00] P. Pan, and H. Schulzrinne, "PF_IPOPTION: A kernel extension
   for IP option packet processing", Technical Memorandum 10009669-02TM,
   Bell Labs, Lucent Technologies, Murray Hill, NJ, June 2000.

   [RFC1819] L. Delgrossi, and L. Berger, "Internet Stream Protocol
   Version 2 (ST2) Protocol Specification - Version ST2+", RFC 1819,
   August 1995.

   [RFC2113] D. Katz, "IP Router Alert Option", RFC 2113, February 1997.

   [RFC2205] R. Braden, L. Zhang, S. Berson, S. Herzog, and S. Jamin,
   "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
   Specification", RFC 2205, Sep 1997.

   [RFC2207] L. Berger, and T. O'Malley, "RSVP Extensions for IPsec Data
   Flows", RFC 2207, September 1997.

   [RFC2210] J. Wroclawski, "The Use of RSVP with IETF Integrated
   Services", RFC 2210, September 1997.

   [RFC2379] L. Berger, "RSVP over ATM Implementation Guidelines", RFC
   2379, August 1998.

   [RFC2380] L. Berger, "RSVP over ATM Implementation Requirements", RFC
   2380, August 1998.

   [RFC2745] A. Terzis, B. Braden, S. Vincent, and L. Zhang, "RSVP
   Diagnostic Messages", RFC 2745, January 2000.

   [RFC2746] A. Terzis, J. Krawczyk, J. Wroclawski, and L. Zhang, "RSVP
   Operation Over IP Tunnels", RFC 2746, January 2000.

   [RFC2747] F. Baker, B. Lindell, and M. Talwar, "RSVP Cryptographic
   Authentication", RFC 2747, January 2000.

   [RFC2749] J. Boyle, R. Cohen, D. Durham, S. Herzog, R. Raja, and A.
   Sastry, "COPS usage for RSVP", RFC 2749, January 2000.

   [RFC2750] S. Herzog, "RSVP Extensions for Policy Control", RFC 2750,
   January 2000.

   [RFC3182] S. Yadav, R. Yavatkar, R. Pabbati, P. Ford, T. Moore, S.
   Herzog, R. Hess, "Identity Representation for RSVP", RFC 3182,

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   October 2001.

   [RFC2814] R. Yavatkar, D. Hoffman, Y. Bernet, F. Baker, and M. Speer,
   "SBM (Subnet Bandwidth Manager): A Protocol for Admission Control
   over IEEE 802-style Networks", RFC 2814, May 2000.

   [RFC2961] L. Berger, D. Gan, G. Swallow, P. Pan, F. Tommasi, and S.
   Molendini, "RSVP refresh overhead reduction extensions", RFC 2961,
   April 2001.

   [RFC2996] Y. Bernet, "Format of the RSVP DCLASS Object", RFC 2996,
   November 2000.

   [RFC2997] Y. Bernet, A. Smith, and B. Davie, "Specification of the
   Null Service Type", RFC 2997, November 2000.

   [RFC2998] Y. Bernet, R. Yavatkar, P. Ford, F. Baker, L. Zhang, M.
   Speer, R. Braden, and B. Davie, "Integrated Services Operation over
   Diffserv Networks", RFC 2998, November 2000.

   [RFC3036] L. Andersson, P. Doolan, N. Feldman, A. Fredette, and B.
   Thomas, "LDP Specification", RFC 3036, January 2001.

   [RFC3175] F. Baker, C. Iturralde, F. Le Faucheur, and B. Davie,
   "Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC 3175,
   September 2001.

   [RFC3181] S. Herzog, "Signaled Preemption Priority Policy Element",
   RFC 3181, October 2001.

   [RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan, and G.
   Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209,
   December 2001.

   [RFC3270] F. Le Faucheur (ed), "Multi-Protocol Label Switching (MPLS)
   Support of Differentiated Services", RFC 3270, May 2002.

   [RFC3303] P. Srisuresh, J. Kuthan, J. Rosenberg, A. Molitor, A.
   Rayhan, "Middlebox communication architecture and framework",
   RFC3303, August 2002.

   [RFC3473] L. Berger (ed), "Generalized MPLS Signaling - RSVP-TE
   Extensions". RFC 3473, January 2003.

   [RFC3474] Z. Lin, and D. Pendarakis, "Documentation of IANA
   assignments for Generalized MultiProtocol Label Switching (GMPLS)
   Resource Reservation Protocol - Traffic Engineering (RSVP-TE) Usage
   and Extensions for Automatically Switched Optical Network (ASON)",
   RFC3474, March 2003.

   [RFC3477] K. Kompella, and Y. Rekhter, "Signalling Unnumbered Links
   in Resource Reservation Protocol - Traffic Engineering (RSVP-TE)",
   RFC 3477, January 2003.


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   [RFC3520] L-N. Hamer, B. Gage, B. Kosinski, and H. Shieh, "Session
   Authorization Policy Element", RFC 3520, April 2003.

   [SGV02] R. Sofia, R. Gu‰rin, and P. Veiga, "An Investigation of
   Inter-Domain Control Aggregation Procedures", International
   Conference on Networking Protocols, ICNP'02, Paris, France, November
   2002.

   [SGV03] R. Sofia, R. Gu‰rin, and P. Veiga. SICAP, a Shared-segment
   Inter-domain Control Aggregation Protocol. High Performance Switching
   and Routing, HPSR 2003, Turin, Italy, June 2003.

   [SGV03b] R. Sofia, R. Gu‰rin, and P. Veiga. A Study of Over-
   reservation for Inter-Domain Control Aggregation Protocols. Technical
   report (short version under submission), University of Pennsylvania,
   May 2003.  Available at
   http://einstein.seas.upenn.edu/mnlab/publications.html.

   [TBA01] A. Talukdar, B. Badrinath, and A. Acharya, "MRSVP: A Resource
   Reservation Protocol for an Integrated Services Network with Mobile
   Hosts", Wireless Networks, vol. 7, no. 1, pp. 5-19. 2001.

   [Thom02] M. Thomas, "Analysis of Mobile IP and RSVP Interactions".
   Internet draft, Work in Progress, October 2002 (draft-thomas-nsis-
   rsvp-analysis-00.txt).

   [Tsch03] H. Tschofenig, "RSVP Security Properties". Internet Draft,
   Work in Progress, February 2004 (draft-ietf-nsis-rsvp-sec-
   properties-04.txt).

   [ZDSZ93] L. Zhang, S. Deering, D. Estrin, and D. Zappala, "RSVP: A
   New Resource Reservation Protocol", IEEE Network, Volume 7, Pages
   8-18, Sep 1993.

   URL links, checked Nov 26 2004:

   [URL1] http://www.atm.tut.fi/list-archive/diffserv/thrd3.html

   [URL2] OPENSIG http://comet.columbia.edu/opensig/

   [URL3] SIGLITE
   http://www.cs.columbia.edu/~pingpan/projects/siglite.html


15.  Authors' Information

      Jukka Manner
      Department of Computer Science
      University of Helsinki
      P.O. Box 68 (Gustav Hallstrominkatu 2b)
      FIN-00014 HELSINKI
      Finland

      Voice:  +358-9-191-51298

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      Fax:    +358-9-191-51120
      E-Mail: jmanner@cs.helsinki.fi

      Xiaoming Fu
      Institute for Informatics
      Georg-August-University of Goettingen
      Lotzestrasse 16-18
      37083 Goettingen
      Germany

      Voice:  +49-551-39-14411
      Fax:    +49-551-39-14403
      E-Mail: fu@cs.uni-goettingen.de










































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16.  Appendix A - Comparison of RSVP to the NSIS Requirements

   This section provides a comparison of RSVP to the requirements
   identified as part of the work in NSIS [RFC3726]. The numbering
   follows the division in the requirements document.

   5.1 Architecture and Design Goals

      5.1.1 NSIS SHOULD provide availability information on request

        RSVP itself does not support query-type of operations. However,
        the RSVP diagnosis messages extension [RFC2745] provides a means
        to query resource availability.

      5.1.2 NSIS MUST be designed modularly

        RSVP was designed to be modular by way of TLV objects, however
        it is regarded being lack of sufficient extensibility in various
        kind of signalling applications.

      5.1.3 NSIS MUST decouple protocol and information

        RSVP is decoupled from the IntServ QoS specifications. Still,
        the concept of sessions in RSVP are somewhat coupled to the
        information it carries.

      5.1.4 NSIS MUST support independence of signaling and network
            control paradigm

        The IntServ information carried by RSVP does not tie the QoS
        provisioning mechanisms.

      5.1.5 NSIS SHOULD be able to carry opaque objects

        RSVP supports this.


   5.2 Signaling Flows

      5.2.1 The placement of NSIS Initiator, Forwarder, and Responder
            anywhere in the network MUST be allowed

        Standard RSVP works only end-to-end, although the RSVP proxy
        [BEGD02] and the Localized RSVP [MSK+04] have relaxed this
        assumption. RSVP relies on receiver-initiation way to perform
        QoS reservations.

      5.2.2 NSIS MUST support path-coupled and MAY support path-
            decoupled signaling

        Standard RSVP is path-coupled, but the SBM work makes RSVP
        somewhat path-decoupled.

      5.2.3 Concealment of topology and technology information SHOULD be

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            possible

        RSVP itself does not provide such capability.

      5.2.4 Transparent signaling through networks SHOULD be possible

        RSVP messages are intecepted and evaluated in each RSVP router,
        and thus they may not cross certain RSVP-routers unnoticed.
        Still, the message processing rules allow unknown RSVP messages
        to be forwarded unharmed.


   5.3 Messaging

      5.3.1 Explicit erasure of state MUST be possible

        Supported by the PathTear and ResvTear messages.

      5.3.2 Automatic release of state after failure MUST be possible

        On error reservation states are torn down with PathTear
        messages.

      5.3.3 NSIS SHOULD allow for sending notifications upstream

        There are two notifications in RSVP, confirm of a reservation
        set-up and tear down of reservation states as a result of
        errors.

      5.3.4 Establishment and refusal to set up state MUST be notified

        PathErr and ResvErr messages provide refusal to set up state in
        RSVP.

      5.3.5 NSIS MUST allow for local information exchange

        RSVP NULL service type [RFC2997] provides such a feature.


   5.4 Control Information

      5.4.1 Mutability information on parameters SHOULD be possible

        Rspec and Adspec are mutable; Tspec is (generally) end-to-end
        not mutable.

      5.4.2 It SHOULD be possible to add and remove local domain
            information

        RSVP aggregation [RFC3175] and NULL service type [RFC2997] can
        provide such a feature.

      5.4.3 State MUST be addressed independent of flow identification


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        RSVP states are tied to the flows, thus this requirement is not
        met.

      5.4.4 Modification of already established state SHOULD be seamless

        Modifications of a reservation is possible with RSVP.

      5.4.5 Grouping of signaling for several micro-flows MAY be
            provided

        Aggregated RSVP and RFC2961 allow this.


   5.5 Performance

      5.5.1 Scalability

        RSVP scales linearly to the number of reservation states.

      5.5.2 NSIS SHOULD allow for low latency in setup

        Setting up an RSVP reservation takes one round-trip time and the
        processing times are each RSVP router.

      5.5.3 NSIS MUST allow for low bandwidth consumption for the
            signaling protocol

        The initial reservations messages can not be compressed, but the
        refresh interval can be adjusted to consume less bandwidth, at
        the expense of possible inefficient resource usage.

      5.5.4 NSIS SHOULD allow to constrain load on devices

        See discussions on RSVP performance (section 4).

      5.5.5 NSIS SHOULD target the highest possible network utilization

        This dedends on the IntServ service types, Controlled Load can
        provide better overall utilization than Guaranteed Service.


   5.6 Flexibility

      5.6.1 Flow aggregation

        Aggregated RSVP and RFC2961 allow this.

      5.6.2 Flexibility in the placement of the NSIS Initiator/Responder

        RSVP allows receiver as initiator of reservations.

      5.6.3 Flexibility in the initiation of state change

        RSVP receivers can initiate the state change during its

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        refreshment.

      5.6.4 SHOULD support network-initiated state change

        As RSVP supports hop-by-hop refreshment, this is made possible.

      5.6.5 Uni / bi-directional state setup

        RSVP is only uni-directional.


   5.7 Security

      5.7.1 Authentication of signaling requests

        Authentication is available in RSVP.

      5.7.2 Request Authorization

        Authorization with a PDP is possible in RSVP.

      5.7.3 Integrity protection

        The INTEGRITY Object is available in RSVP.

      5.7.4 Replay protection

        The INTEGRITY Object to replay protect the content of the
        signaling messages between two RSVP nodes.

      5.7.5 Hop-by-hop security

        The RSVP security model works only hop-by-hop.

      5.7.6 Identity confidentiality and network topology hiding

        The INTEGRITY Object can be used for this purpose.

      5.7.7 Denial-of-service attacks

        Challenging with RSVP.

      5.7.8 Confidentiality of signaling messages

        Not supported by RSVP.

      5.7.9 Ownership of state

        Challenging with RSVP.


   5.8 Mobility

      5.8.1 Allow efficient service re-establishment after handover

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        Works for upstream but may not be achieved for the downstream
        if mobility is not noticed at the cross-over router.


   5.9 Interworking with other protocols and techniques

      5.9.1 MUST interwork with IP tunneling

        RFC 2746 discusses these issues.

      5.9.2 MUST NOT constrain either to IPv4 or IPv6

        RSVP supports both IP versions.

      5.9.3 MUST be independent from charging model

        RSVP does not discuss this.

      5.9.4 SHOULD provide hooks for AAA protocols

        COPS and RSVP work together.

      5.9.5 SHOULD work with seamless handoff protocols

        Not supported by RSVP. Still, RFC2205 suggests that route
        changes should be indicated to the local RSVP daemon, which can
        then initiate state refresh.

      5.9.6 MUST work with traditional routing

        RSVP expects traditional routing.


   5.10 Operational

      5.10.1 Ability to assign transport quality to signaling messages

        This is a network design issue, but is possible with DiffServ.

      5.10.2 Graceful fail over

        RSVP supports this.

      5.10.3 Graceful handling of NSIS entity problems

        RSVP itself does not supports this.









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