Internet Engineering Task Force                                J. Manner
Internet-Draft                                                 T. Suihko
Expires: March, 2005                                             M. Kojo
                                                            M. Liljeberg
                                                          K. Raatikainen
                                                         September, 2004

                             Localized RSVP

Status of this Memo

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   Guaranteed QoS for multimedia applications is based on reserved
   resources in each node on the end-to-end path. Even if the
   correspondent node does not support QoS, it would be useful to be
   able to reserve at least local resources at the access network,
   especially wireless link resources. Additionally, for mobile nodes
   the continuity of QoS is disturbed due to end-to-end signaling or
   slow re-reservations of resources after each handover. This draft
   proposes a simple enhancement to RSVP, so that initial resource
   reservations and re-reservations due to host mobility can be done
   locally in an access network.

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Changes since -03
   - Updated boilerplates
   - Removed discussion on using the CAP Object (not really an option)
   - Removed discussion and suggestion on using anycast or multicast
     addresses when sending the initial Path Request. This is more
     like a hack and trick, and not really good and clear engineering.
   - Updated references and author information

Changes since -02
   - Clarified parts of the text, e.g. Section 2.4

Changes since -01
   - Some clarifications and editorial changes

Table of Contents

   1 Introduction .................................................    2
   1.1 Related work ...............................................    3
   2 Local QoS Support ............................................    4
   2.1 Upstream transfers .........................................    5
   2.2 Downstream transfers .......................................    6
   2.3 Additional functionality ...................................    7
   2.4 Addressing Issues ..........................................    8
   2.5 Interworking Issues ........................................    9
   3 Fast local repair for mobile nodes ...........................   11
   4 Security Consideration .......................................   13
   5 IANA Considerations ..........................................   14
   6 Summary ......................................................   14
   7 Normative References .........................................   15
   8 Non-Normative References .....................................   15
   9 Authors' Addresses ...........................................   16

1.  Introduction

   Future mobile access networks will be based on IP technology. This
   implies that, on the network layer, all traffic, both traditional
   data and streamed data like audio or video, is transmitted as
   packets. Increasingly popular multimedia applications would benefit
   from better than best-effort service from the network, a forwarding
   service with strict Quality of Service (QoS) with guaranteed minimum
   bandwidth and bounded delay. Other applications, such as electronic
   commerce, network control and management, and remote login
   applications, would also benefit from a differentiated treatment.

   The IETF has two main models for providing differentiated treatment
   of packets in routers. The Integrated Services (IntServ) model [1]
   together with the Resource Reservation Protocol (RSVP)  [2] [3]
   provides per-flow guaranteed end-to-end transmission service. The
   Differentiated Services (DiffServ) framework [4] provides non-
   signaled flow differentiation that usually provides, but does not
   guarantee, proper transmission service.

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   However, these architectures have weaknesses, for example, RSVP
   requires support from both communication end points and from the
   intermediate routers, and the protocol has performance issues in
   mobile environments.  DiffServ can only provide statistical
   guarantees and is not well suited for dynamic environments. The
   Internet Architecture Board has outlined additional issues related to
   these two architectures [5].

   Let us consider a scenario, where a fixed network correspondent node
   (CN) would be sending a multimedia stream to an end host behind a
   wireless link. If the correspondent node does not support RSVP it
   cannot signal its traffic characteristics to the network and request
   specific forwarding services. Likewise, if the correspondent node is
   not able to mark its traffic with a proper DiffServ Code Point (DSCP)
   to trigger service differentiation, the multimedia stream will get
   only best-effort service which may result in poor visual and audio
   quality in the receiving application. Even if the connecting wired
   network is over-provisioned, an end host would still benefit from
   local resource reservations, especially in wireless access networks,
   where the bottleneck resource is most probably the wireless link.

   We propose a slight modification to RSVP that allows distinguishing
   local network reservations from the end-to-end reservations. The end
   host does not need to know the access network topology or the nodes
   that will reserve the local resources. The reservation message itself
   identifies the intention and the access network will find the correct
   network node(s) to respond to the reservation. Note that the scheme
   is not tied to only mobile networks but can be used in any access
   network that needs flexible local resource allocations. The first
   sketch of this solution appeared in [10] and [11], although some
   implementation ideas have changed since.

   The localized RSVP signaling would fit well, for example, with a SIP
   session, where a call set up can have a pre-condition: if the request
   for local resources is successful, the end-host can send the COMET
   message and make the call "ring" [15]. Both ends would use their own
   local reservations.

   All mobility-related terminology in this document are taken from
   [16]. Therefore, the commonly used term 'access router' (AR) means
   the 'default router'.

1.1.  Related work

   Currently we can identify two ways to signal QoS requirements to an
   access network: DiffServ Code Points (DSCP) and RSVP with IntServ. In
   the DiffServ-based solution an end host can mark the upstream packets
   with proper DSCP values, but for the downstream the gateway on the
   edge of the access network must be able to identify and handle the
   preferred streams. This can be accomplished with default values for
   different micro flows in the Service Level Agreement negotiated
   between the client and the access network service provider.

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   An alternative way to make use of DiffServ could be through a
   Bandwidth Broker [6] [7] [8] that dynamically returns the proper code
   point for each flow: when the first packet of a flow arrives at the
   access network edge router, it requests the proper code point from
   the Bandwidth Broker. The router maintains a mapping from micro flow
   identification to the DiffServ code point (soft state) so that future
   packets can be directly identified and labeled. Still, this would
   require a protocol that the end host could use to dynamically adjust
   the mapping information stored at the access network edge for the
   incoming traffic.

   RSVP can provide the signaling mechanism for QoS requirements to the
   access network. For upstream reservations, the end host would send
   the Path message to the access network edge router, which would
   return the Resv message and set up the reservations. The edge router
   would act as an RSVP proxy [9]. However, the reservation in the
   downlink direction is not as straightforward since the downlink
   reservation needs to be initiated by the RSVP proxy. We would need a
   way to trigger the proxy to initiate the RSVP signaling for a
   downlink flow.

   Thus, these mechanisms do not seem to solve the problem entirely. The
   DiffServ mechanisms cannot provide explicit resource reservations.
   The problem with the RSVP proxy approach is that the proxy cannot
   automatically distinguish reservations that would be answered by the
   correspondent node and reservations that would require interception.
   Additionally, the RSVP proxy needs a way to know when to allocate
   resources for incoming flows. Mobile access networks also add to the
   problems, since mobile nodes can frequently change their point of
   attachment in the network and resource allocations need to be re-
   arranged, including changing the serving RSVP proxy.

2.  Local QoS Support

   The usual signaling model of RSVP includes the data sender and
   receiver, and a network of RSVP routers. The data sender initiates
   the RSVP signaling by sending the Path message. This message is
   routed through the network, setting states in RSVP routers, and
   finally arriving at the data receiver. The receiver then responds to
   the signaling by sending the Resv message, which applies the
   reservation for the data stream.

   If the data receiver is not RSVP-aware, it can not respond to the
   signaling and make the resource reservation happen. Similarly, if the
   receiver is RSVP-aware, but the sender is not, the sender can not
   initiate the signaling for the resource reservation.

   In the Localized RSVP scheme, we expect the local end host to be
   RSVP-aware and we add an RSVP-aware application to a router in the
   local access network. This 'proxy' is called the Localized RSVP Proxy
   server (LRSVP proxy) and is located somewhere within the local access
   network - a good place would be the access network gateway. For local
   reservations, the proxy acts on behalf of correspondent nodes.  In

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   this discussion, from a software engineering point of view, the proxy
   is its own process running on the router. Thus, the following three
   logical functions are kept separate: basic IP routing, basic RSVP
   message processing, and LRSVP proxy functionality.

   Now, in order to distinguish local reservations from end-to-end
   reservations, we use one bit in the unused Flags field in the RSVP
   Session Object. The Local Indication (LI) bit (currently we use bit
   0x8) is used to differentiate reservations that are internal to the
   access network. When the bit is set the RSVP message is part of local
   resource signaling and the RSVP router running the proxy will not
   forward the message to the next hop but instead give the message to
   the RSVP-application running on the router. A default value of zero
   indicates standard end-to-end signaling, where the proxy application
   is not concerned.

   We also need a second bit, the Expedited Refresh (ER) bit (currently
   we use bit 0x4), to indicate that a Path message is sent as a refresh
   to a broken path and must be forwarded immediately. This indication
   is needed because each RSVP hop propagates a Path message before a
   timeout only if the Path state has changed - when a route changes at
   the receiver end of the data flow, a Path message is needed to set up
   again the Path state. This is discussed in more detail later.

   When the local end host wants to make a resource reservation for a
   downstream flow, it needs a Path message from a node on the data
   path. If the data sender is not RSVP-aware, the local end host can
   trigger the LRSVP proxy to send the Path message on behalf of the
   data sender. A new message type called "Path Request", with an
   initial message type number 8, is used to request a Path message from
   the local RSVP proxy. This message has the same structure as a
   standard Path message.

   A second message called "Path Request Tear", with an initial message
   type number 9, is used to tear down a downstream reservation. Note
   that due to the new bits and message types, all RSVP routers inside
   the access network must be upgraded with the LRSVP extension.

   When a local end host wants to reserve resources in the local access
   network, it uses the LI flag in RSVP messages to indicate a local
   reservation. The structure of the RSVP messages follows the RSVP
   standard. When the router running the LRSVP proxy receives an RSVP
   message with the LI bit set it will notice that the flag was set and
   does not forward the message further to the next hop. The RSVP daemon
   on the router gives the message to the local RSVP application, which
   responds according to the following description.

2.1.  Upstream transfers

   Setting local upstream reservations is straightforward and follows
   closely the standard RSVP functionality. The local end host sends the
   usual Path message, but sets the LI flag bit in the Session Object.
   The Session Object of the message defines the destination of the flow

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   that will eventually be transmitted from the local end host, and the
   Sender Template provides information about the local end host itself.

   [END HOST]  [Access Router]  [X-OVER ROUTER]     [PROXY]     [CN]
       |              |               |               |         |
       |------------- Path towards CN (LI) ---------->|         |
       |              |               |               |         |
       |              |               |     (proxy intercepts)  |
       |              |               |               |         |
       |              |               |<---- Resv ----|         |
       |              |<---- Resv ----|               |         |
       |<---- Resv ---|               |               |         |
       |              |               |               |         |

   Figure 1: Local Upstream reservation

   The Path message is routed within the access network and sets the
   Path state in RSVP routers. When the LRSVP proxy receives the Path
   message, it notes due to the LI bit that the reservation is meant to
   stay within the access network and responds with a Resv message. It
   will not forward the Path message further to the next hop. When a
   Resv message arrives at the local end host, the resources for the
   session defined in the Path message have been allocated.

2.2.  Downstream transfers

   Before setting a downstream resource reservation, the local end host
   needs to be aware of the data senders. For multimedia communications,
   a session is usually initiated with application layer protocols like
   SIP [15] or RTSP [12].  Based on this correspondence, the local end
   host knows the necessary information about the sender. Another, more
   coarse reservation could be set, for example, for browsing different
   audio servers; the local end host would indicate in the RSVP messages
   that the sender will use UDP. It is, therefore, possible to make
   resource reservations for any sender that wants to communicate with
   the local end host. However, in order to allow for more accurate QoS
   support, more information should be given. The way to find this
   information is out of scope of this document.

   In order to set up a local downstream reservation we need a way to
   signal the LRSVP proxy to initiate the RSVP reservation set up on
   behalf of the sender(s), that is, to send a Path message. To achieve
   this, the local end host sends the Path Request message with the LI
   flag bit set (Fig. 2).  The Path Request message is identical to a
   standard Path message apart from the message type field. The Session
   Object must include information about the recipient, the local end
   host in this case, and the Sender Template must define the expected
   sender(s). The Traffic specification (Tspec) can either be based on
   the local end user's wishes, a best estimate of the incoming traffic
   characteristics, or on application level session signaling prior to
   the transfer.

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   [END HOST]  [Access Router]  [X-OVER ROUTER]     [PROXY]    [CN]
       |              |               |               |         |
       |------------ Path Request towards CN (LI) --->|         |
       |              |               |               |         |
       |              |               |     (proxy intercepts)  |
       |              |               |               |         |
       |              |               |<- Path (LI) --|         |
       |              |<- Path (LI) --|               |         |
       |<- Path (LI) -|               |               |         |
       |              |               |               |         |
       |- Resv (LI) ->|               |               |         |
       |              |-- Resv (LI) ->|               |         |
       |              |               |-- Resv (LI) ->|         |
       |              |               |               |         |

   Figure 2: Local downstream reservation

   When the LRSVP proxy receives this message, it detects that the
   message is meant to stay within the access network. The message type
   indicates that the proxy should initiate an RSVP reservation for a
   downstream flow and use the information in the message to fill the
   objects in a Path message. The proxy now generates a Path message
   that includes the parameter values in the Path Request message and
   sends it towards the local end host.

   When the local end host receives the Path message, it responds with a
   Resv message with the LI flag set. This reserves the downstream
   resources within the access network for the senders originally
   identified by the local end host.

   The Path Request message can also be used end-to-end, to request the
   correspondent node to initiate a resource reservation. In this case,
   the LI bit must not be set, since it would stop the message at the
   local access network.

2.3.  Additional functionality

   All the other features of RSVP are used with LRSVP in the standard
   way including the local repair mechanism and reservation tear down.
   Downstream reservations are torn down with the Path Request Tear
   message. The operation follows that of the Path Request: the message
   does not change states within the network, but only triggers the
   proxy to send a Path Tear message towards the end host for the
   specified session.

   All messages used for local reservations must have the LI flag set in
   order to keep the signaling within the access network.  Intermediate
   RSVP routers between the local end host and the LRSVP proxy should
   not process the Path Request message and they should forward it as an
   ordinary IP packet. An enhancement to the local repair changes this
   operation and is discussed later.

   The proposed scheme also allows RSVP to be used to signal DiffServ

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   Code Points in a DiffServ access network using the RSVP DCLASS object
   [13]. The DCLASS object is used to represent and carry DiffServ code
   points within RSVP messages.  The local end host can use the DCLASS
   object to instruct the LRSVP proxy to mark incoming traffic with
   certain DiffServ code points to trigger different forwarding behavior
   within the DiffServ access network.  The local end host, however,
   needs to be aware of the different code point values and the related
   services, especially if other than standardized code points are used.
   This information can be part of host auto-configuration, for example.

   Furthermore, the proposed signaling can be used at both ends of a
   data stream. For example, if the two end hosts in different access
   networks are communicating with each other, both of them could use
   the mechanism to allocate resources, for example, in their own access
   networks, independently of each other. This could happen, if the two
   access networks had a different view of QoS, one uses only IntServ
   and RSVP, while the other also uses DiffServ. In such a scenario,
   however, it may be more practical to use RSVP end-to-end, even if the
   core network connecting the two access networks does not support

2.4.  Addressing Issues

   When the local end host sends Path or Path Request messages, it needs
   to use some IP address as the destination in the IP header. There are
   various options about which address the local end host can or can not
   use. The local end host must use in priority order (if known):

   1. The address of the correspondent host,
   2. The address of a proper LRSVP proxy,
   3. The address of the next-hop RSVP router, or
   4. The address of the default router.

   The first option may not be possible, if the end host wants to
   allocate resources only for certain services regardless of the
   sender, HTTP, for example. The second possible address could be given
   through auto-configuration. The third option would be to send the IP
   packet to the next-hop RSVP router, if the end host has knowledge of
   it - ideally, this would be the default router, in a mobile access
   network, it would be the access router.

   Finally, if any of the earlier addresses are not known, the end host
   may try to send the RSVP packet to the default router, and see if the
   router is also running an RSVP daemon and could handle the
   reservation attempt. If the default router is not running an RSVP
   daemon, it will return an ICMP error message.

   A further concern arises if the access network has several inbound
   routes. It is possible that the local downstream reservation
   initiated by the end host is set on a wrong LRSVP proxy, one that
   will not get the packets arriving to the end host. This seems more of
   a network design issue and therefore the access network operator must
   locate the LRSVP proxies based on the packet routing - the proxies

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   could even be co-located at the access routers.

2.5.  Interworking Issues

   The Localized RSVP makes use of two bits in the Session Object and
   adds two new message types. There can be situations where such a
   currently non-standard message arrives at a standard RSVP router.

   According to the message processing rules in RFC2209 [18], the Path
   Request and Path Request Tear messages would be forwarded intact by
   standard RSVP routers. However, for standard RSVP message, the bits
   used by LRSVP may or may not be kept between RSVP hops, and, thus,
   the indication of local signaling or the need for an expedited
   refresh may be lost. Therefore, all RSVP routers within an access
   network wanting to support local reservations must be set to keep the
   bits intact.

   In one scenario, the local network of the end host would not
   understand the LRSVP extension or even standard RSVP. Thus, Path
   messages with the LI bit and Path Request message can be routed out
   of the local network. If the local network of the correspondent node
   has support for LRSVP, that LRSVP proxy gets the Path or Path Request
   message with the LI bit set from the external network. The proxy must
   drop the message and respond with a PathErr message and use a new
   error code called "LRSVP not supported". This would inform the host
   that LRSVP is not supported and it still can try end-to-end

   Another interesting scenario arises when the correspondent node is a
   mobile node and the parties use route optimization. It can happen,
   that the correspondent node is actually in the same access network as
   the end host using LRSVP, and either or both nodes try to reserve
   local resources independently of each other. Now it is possible that
   Path and Path Request messages with the LI bit set are routed
   directly to the correspondent node, without going through a local
   network LRSVP proxy.

   A solution would be that end hosts can also perform the same
   functions as an LRSVP proxy, that is, answer to Path messages with
   the LI bit set and, most importantly, handle Path Request messages as

   o If an end host receives an unsolicited Path message with the LI bit
   set, it should respond with a Resv message and not set the LI bit.
   The reason is that that if the LRSVP proxies drop Path messages with
   the LI bit set coming from external networks, the local end hosts can
   trust that if they receive such a message, it must have (if the
   network is properly configured) arrived from a node in the local
   access network. Now, if our end host that sent the Path message
   receives the Resv without the LI bit, it can use this as an
   indication that the correspondent node is in the local access network
   and may remove the LI bit in subsequent messages belonging to the
   same session.

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   o Similarly, if the correspondent node receives a Path Request
   message, it should respond with a Path message that does not have the
   LI bit set. Again, if our end host receives a Path message without
   the LI bit set in response to the local Path Request sent earlier, it
   can use this as an indication that the correspondent node is in the
   local domain and it may remove the LI bit in subsequent messages
   belonging to the same session.

   Now, if the correspondent node moves again and changes access
   networks, the signaling is already set to standard end-to-end mode
   and reservations in the new RSVP-aware access network would be set in
   place. However, changing access networks implies most probably a
   change in the IP address assigned to the CN, which forces a re-
   reservation of resources.

   In the latter scenario, it is quite possible, that the mobile
   correspondent node, located in the same access network as our end
   host, is not (L)RSVP aware. Thus, it cannot respond to the RSVP
   messages and local, actually, any kind of RSVP-based, reservations
   are not possible.

   Moreover, the location of the LRSVP proxy may yet affect the
   signaling of two nodes within the same access network. Consider the
   case where each access router would also host an LRSVP proxy. Now if
   the two communicating nodes are connected to different access
   routers, the two nodes may use their own local reservations on the
   last-hop link, but also a standard end-to-end reservation is

   A further issue concerns the interactions between local and end-to-
   end reservations: could a local reservation be 'upgraded' into an
   end-to-end reservation? This should be possible for both directions:

   o If the proxy receives a fully standard Path message from the local
   network with the same session information as an existing local
   reservation, it must forward the message as usual, but set a pending
   Path state indication for the end-to-end reservation. If a Resv
   arrives from the external network for this same session, it must
   change the reservation to an end-to-end reservation.

   o If the proxy receives a Path Request message from the local network
   without the LI bit set, it must forward the message to the IP
   destination address. If the proxy receives later a Path message from
   the external network for an existing local session, it must set a
   pending state for the end-to-end reservation. If a Resv is received
   from the local end host without the LI bit set, the proxy must change
   its state for the session to 'end-to-end' (by removing a local-
   indication from its session structures) and forward the Resv message
   further to the external network.

   Thus, it would be possible to upgrade a local session to end-to-end
   status. It is not clear whether there is a need for an end-to-end
   session to be 'downgraded' into a local session.

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   Note that when the resource signaling is going end-to-end, the local
   repair functionality may be affected. If both nodes use only local
   reservations, the local repair at either end is propagated at most to
   the local LRSVP proxy. With end-to-end reservations, the local repair
   may be propagated further away from the moving node and its access

3.  Fast local repair for mobile nodes

   The RSVP standard [2] 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 Path state of the
   reservation on the new route and a subsequent Resv message will apply
   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. The RSVP specification also says
   that 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 [2]). However, for example, Mobile IP, does not
   affect routing directly in routers, and thus mobility may not be
   noticed at intermediate RSVP routers.

   When the mobile node has moved, it can send a Path message for each
   upstream resource reservation and initiate the standard local repair
   mechanism (Fig. 3). If there is no cross-over router, and the Path
   message arrives at a new LRSVP proxy, the proxy will reply to the
   Path with a Resv, similarly as it would for a new resource
   reservation request (what this actually looks like to the new proxy).

       |             |              |                 |             |
       |-- Path towards CN (LI)---->|                 |             |
       |             |              |                 |             |
       |             |  (X-over router intercepts)    |             |
       |             |              |                 |             |
       |             |<- Resv (LI) -|                 |             |
       |<- Resv (LI)-|              |                 |             |
       |             |              |                 |             |

   Figure 3: Fast upstream reservation

   For the downstream, the mobile node will need to wait until it
   receives a Path message, setting up the Path state on the new route.
   Only after receiving the Path message, the mobile can send a Resv
   message to re-reserve the downstream resources.

   The Path Request message can be used in mobile networks to initiate a
   faster local repair of downstream reservations on behalf of a mobile
   node that changed access routers during an ongoing RSVP session. When
   the mobile node changes its access router in the network, it should

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   send the Path Request message immediately after the handover (Fig 4).

    |               |               |               |               |
    |-------------- Path Request towards CN (LI,ER) --------------->|
    |               |               |               |               |
    |               |               |               |<-Path (LI,ER)-|
    |               |               |<-Path (LI,ER)-|               |
    |               |<-Path (LI,ER)-|               |               |
    |<-Path (LI,ER)-|               |               |               |
    |               |               |               |               |
    |- Resv (LI) -->|               |               |               |
    |               |- Resv (LI) -->|               |               |
    |               |               |               |               |

   Figure 4: Fast downstream reservation

   The message must have the ER bit set to indicate that the request is
   for an existing session and triggered due to movement. The Path
   Request message is forwarded through the intermediate RSVP routers
   until it arrives at the LRSVP proxy. The message would then instruct
   the proxy to initiate a local repair by sending the needed Path
   message. The proxy must set the ER bit in the Session Object to
   indicate that this Path message is not an ordinary refresh message
   but instead triggered by a routing change and therefore must be
   forwarded immediately to the next hop. If the ER bit is not set, the
   RSVP router in Fig. 4 would not forward the Path message immediately
   towards the mobile node but, instead, would wait until its own
   scheduled refresh timeout.

   If the movement of the mobile node results in packets to flow through
   a new LRSVP proxy, the Path Request message would re-reserve the
   local resources for the new path. In this case, the proxy notes that
   the ER bit is set, but, since there is no existing state, it will
   initiate a new reservation. The ER bit must not be set in the
   following Path message since the reservation is a new one for this

   A enhancement to the scheme would allow a cross-over RSVP router that
   has the reservation for the mobile node stored on a different
   interface to send the needed Path message (Fig. 5). RSVP routers
   inside the access network would look into Path Request messages. If
   the router notices it is the cross-over router, it sends a Path
   message towards the local end host. If an RSVP router sends the Path
   message, it must not send the Path Request message any further. This
   requires more processing from intermediate RSVP routers, but allows
   for faster state updates. This functionality would be especially
   important when the session is end-to-end instead of local: the Path
   Request message would not go to the correspondent node, but trigger
   the closer cross-over router to repair the local path of the

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   [END HOST]        [NEW AR]        [X-OVER ROUTER]        [PROXY]
       |                 |                  |                  |
       |- Path Request towards CN (LI,ER) ->|                  |
       |                 |                  |                  |
       |                 |      (X-over router intercepts)     |
       |                 |                  |                  |
       |                 |<--- Path (LI) ---|                  |
       |<-- Path (LI) ---|                  |                  |
       |                 |                  |                  |
       |--- Resv (LI) -->|                  |                  |
       |                 |--- Resv (LI) --->|                  |
       |                 |                  |                  |

   Figure 5: Enhancement of the fast downstream reservation

   The LI flag must be set in all RSVP refresh messages if the
   reservation is set for the local access network.  This will prevent a
   refresh message, like the Path Request message, to be routed out of
   the access network.

4.  Security Consideration

   The Path Request message triggers most processing at the LRSVP proxy.
   This could potentially be used for Denial of Service attacks. A
   possible solution is to make RSVP daemons located on access routers
   make a sanity check on all Path Request (and Path Request Tear)
   messages: the receiver of the stream must be a node on a link
   connected to the AR.  This has the benefit that the proxy may trust
   that the access router has validated the message; this can be seen as
   distributed processing of the authentication and authorization data.
   The same considerations apply for the Path message. In order to
   secure any RSVP signaling, a security association must be set up
   between the local end hosts and the access routers.

   The RSVP daemon at the end hosts and LRSVP proxy must also modify
   their security/sanity checks to allow the end host to send the Path
   Request with apparently suspicious session information (identifying
   the correspondent node(s)). Also, the proxy must be able to send RSVP
   messages "on-behalf" of external network nodes.

   The LRSVP proxy must be configured to identify its ingress and egress
   interfaces. If the proxy receives a Path or a Path Request message
   with the LI bit set from outside the access network, it must drop the

   The two new messages can make use of the standard RSVP INTEGRITY and
   POLICY objects. This requires that the MN and ARs share the required
   keys. For the remaining functionality, the security considerations
   with standard RSVP apply, which are analyzed well by the NSIS WG in

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5.  IANA Considerations

   IANA needs to allocate the two flag bits in the RSVP Session Object,
   the LI and ER bits. In addition, IANA needs to give two RSVP message
   type numbers to the Path Request and Path Request Tear messages and
   one Error Type indicating that a local resource reservation is not

6.  Summary

   In summary, the Localized RSVP requires the following changes in the
   standard RSVP protocol:

   a) A new message type and number, named Path Request (initially
   number 8).

   b) A new message type and number, named Path Request Tear (initially
   number 9).

   c) A bit from the Session Object for the use as the Local Indication
   (LI) (initially bit 0x8).

   d) A bit from the Session Object for use as the Expedited Refresh
   (ER) indication (initially bit 0x4).

   e) An RSVP router must keep the LI bit set in all messages belonging
   to that session, if it encounters packets with the bit set.

   f) An RSVP router that is not also a proxy, must forward an RSVP
   packet with a message type "Path Request" without storing state.

   g) An RSVP router that is not also a proxy, must forward an RSVP
   packet with a message type "Path Request Tear" without affecting the
   stored state.

   h) An access network RSVP router should be able to use the Path
   Request as an indication of the need for a local repair. This can
   enable faster reservation set up following a handover. This affects
   point f), because the router that receives a Path Request must first
   check if it has the Path state stored on another network interface.
   If one is present, the Path Request message should not be forwarded
   to the next hop and instead the router must send a Path message
   towards the mobile node.

   i) A new error code to indicate that the access network does not
   support local reservations. If local resources cannot be requested,
   the end-host can always try to do end-to-end signaling.

   To summarize, these changes are small and would make RSVP more
   appealing as a signaling protocol for IP access networks. The changes
   are required only within access networks, unless the Path Request
   message is deemed useful to use end-to-end through the Internet.

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7.  Normative References

   [1] R. Braden, D. Clark, S. Shenker, "Integrated Services in the
   Internet Architecture: an Overview". RFC 1633, June 1994.

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

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

   [4] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, "An
   Architecture for Differentiated Services". RFC 2475, December, 1998.

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

   [18] R. Braden, "Resource ReSerVation Protocol (RSVP) -- Version 1
   Message P rocessing Rules". RFC 2209, September 1997.

8.  Non-Normative References

   [5] G. Huston, "Next Steps for the IP QoS Architecture".  RFC 2990,
   November 2000.

   [6] K. Nichols, V. Jacobson, L. Zhang, "A Two-bit Differentiated
   Services Architecture for the Internet". RFC 2638, July 1999.

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

   [8] Phil Chimento and Ben Teitelbaum, "QBone Bandwidth Broker
   Architecture". The Internet2 initiative, June 2000.

   [9] S. Gai, D. G. Dutt, N. Elfassy, Y. Bernet, "RSVP Proxy". Internet
   Draft (work in progress), March 2002 (expired) (draft-ietf-rsvp-

   [10] Jukka Manner and Kimmo Raatikainen, "Extended Quality-of-Service
   for Mobile Networks". Proceedings of the 9th International Workshop
   on Quality of Service (IWQoS), June 2001, pp. 275-280. Published in
   the series Springer Lecture Notes in Computer Science (LNCS) 2092.

   [11] IST-BRAIN Project, "Deliverable D2.2: BRAIN architecture
   specifications and models, BRAIN functionality and protocol
   specification".  March 2001, (available at:

   [12] H. Schulzrinne, A. Rao, R. Lanphier, "Real Time Streaming
   Protocol (RTSP)". RFC 2326, April 1998.

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   [15] J. Rosenberg et al., "SIP: Session Initiation Protocol". RFC
   3261, June 2002

   [16] J. Manner, and M. Kojo, "Mobility related terminology". RFC
   3753, June 2004.

   [17] H. Tschofenig, "RSVP Security Properties". Internet Draft (work
   in progress), September 2004.

9.  Authors' Addresses

   Questions about this document may be directed to:

   Jukka Manner
   Department of Computer Science
   University of Helsinki
   P.O. Box 68

   Voice:  +358-9-191-51298
   Fax:    +358-9-191-51120

   Markku Kojo
   Department of Computer Science
   University of Helsinki
   P.O. Box 68

   Voice:  +358-9-191-51305
   Fax:    +358-9-191-51120

   Kimmo Raatikainen
   Department of Computer Science
   University of Helsinki
   P.O. Box 68

   Voice:  +358-50-483-6275
   Fax:    +358-9-191-51120

   Tapio Suihko
   VTT Information Technology
   P.O. Box 1203
   FIN-02044 VTT

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   Voice:  +358-9-456-6078
   Fax:    +358-9-456-7028

   Mika Liljeberg
   Nokia Research Center
   P.O. Box 407
   FIN-00045 Nokia Group

   Voice: +358-50-4836791


   This work has been partially performed in the framework of the IST
   project IST-2000-28584 MIND, which is partly funded by the European
   Union.  The authors would like to acknowledge the help of their
   colleagues in preparing this document, in particular Eleanor Hepworth
   and Alberto Lopez.

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an

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