path: root/doc/rfc/rfc2209.txt

Network Working Group                                          R. Braden
Request For Comments: 2209                                           ISI
Category: Informational                                         L. Zhang
                                                                    UCLA
                                                          September 1997

                Resource ReSerVation Protocol (RSVP) --
                   Version 1 Message Processing Rules

Status of this Memo


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

Abstract

   This memo contains an algorithmic description of the rules used by an
   RSVP implementation for processing messages.  It is intended to
   clarify the version 1 RSVP protocol specification.

   This memo provides a generic description of the rules for the
   operation of Version 1 of RSVP [RFC 2205].  It is intended to outline
   a set of algorithms that will accomplish the needed function,
   omitting many details.

1. GENERIC DATA STRUCTURES

   This memo assumes the generic interface calls defined in [RFC 2005]
   and the following data structures.  An actual implementation may use
   additional or different data structures and interfaces.  The data
   structure fields that are shown are required unless they are
   explicitly labelled as optional.

   o    PSB -- Path State Block

        Each PSB holds path state for a particular (session, sender)
        pair, defined by SESSION and SENDER_TEMPLATE objects,
        respectively, received in a PATH message.











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        PSB contents include the following values from a PATH message:

        -    Session

        -    Sender_Template

        -    Sender_Tspec

        -    The previous hop IP address and the Logical Interface
             Handle (LIH) from a PHOP object

        -    The remaining IP TTL

        -    POLICY_DATA and/or ADSPEC objects (optional)

        -    Non_RSVP flag

        -    E_Police flag

        -    Local_Only flag

        In addition, the PSB contains the following information provided
        by routing: OutInterface_list, which is the list of outgoing
        interfaces for this (sender, destination), and IncInterface,
        which is the expected incoming interface.  For a unicast
        destination, OutInterface_list contains one entry and
        IncInterface is undefined.

        Note that there may be more than one PSB for the same (session,
        sender) pair but different incoming interfaces.  At most one of
        these, which will have the Local_Only flag off, will be the PSB
        used for forwarding PATH messages downstream; we will refer to
        it as the "forwarding PSB" in the following.  The other PSB's
        will have the Local_Only flag on and an empty
        OutInterface_list.h The Local_Only flag is needed to correctly
        match PSB's against RSB's, by the rules of [RFC 2205].

   o    RSB -- Reservation State Block

        Each RSB holds a reservation request that arrived in a
        particular RESV message, corresponding to the triple:  (session,
        next hop, Filter_spec_list).  Here "Filter_spec_list" may be a
        list of FILTER_SPECs (for SE style), a single FILTER_SPEC (FF
        style), or empty (WF style).  We define the virtual object type
        "FILTER_SPEC*" for such a data structure.






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        RSB contents include:

        -    Session specification

        -    Next hop IP address

        -    Filter_spec_list

        -    The outgoing (logical) interface OI on which the
             reservation is to be made or has been made.

        -    Style

        -    Flowspec

        -    A SCOPE object (optional, depending upon style)

        -    RESV_CONFIRM object that was received (optional)

   o    TCSB -- Traffic Control State Block

        Each TCSB holds the reservation specification that has been
        handed to traffic control for a specific outgoing interface.  In
        general, TCSB information is derived from RSB's for the same
        outgoing interface.  Each TCSB defines a single reservation for
        a particular triple: (session, OI, Filter_spec_list).   TCSB
        contents include:

        -    Session

        -    OI (Outgoing Interface)

        -    Filter_spec_list

        -    TC_Flowspec, the effective flowspec, i.e., the LUB over the
             corresponding FLOWSPEC values from matching RSB's.
             TC_Flowspec is passed to traffic control to make the actual
             reservation.

         -   Fwd_Flowspec, the updated object to be forwarded
             after merging.

        -    TC_Tspec, equal to Path_Te, the effective sender Tspec.

        -    Police Flags

             The flags are E_Police_Flag, M_Police_Flag, and
             B_Police_Flag.



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        -    Rhandle, F_Handle_list

             Handles returned by the traffic control interface,
             corresponding to a flowspec and perhaps a list of filter
             specs.

        -    A RESV_CONFIRM object to be forwarded.

   o    BSB -- Blockade State Block

        Each BSB contains an element of blockade state.  Depending upon
        the reservation style in use, the BSB's may be per (session,
        sender_template) pair or per (session, PHOP) pair.  In practice,
        an implementation might embed a BSB within a PSB; however, for
        clarity we describe BSB's independently.

        The contents of a BSB include:

        -    Session

        -    Sender_Template (which is also a filter spec)

        -    PHOP

        -    FLOWSPEC Qb

        -    Blockade timer Tb

        The following Boolean Flag variables are used in this section:
        Path_Refresh_Needed, Resv_Refresh_Needed, Tear_Needed,
        Need_Scope, B_Merge, and NeworMod.  Refresh_PHOP_list is a
        variable-length list of PHOPs to be refreshed.

2. PROCESSING RULES

   MESSAGE ARRIVES

   Verify version number and RSVP checksum, and discard message if any
   mismatch is found.

   If the message type is not PATH or PTEAR or RACK and if the IP
   destination address does not match any of the addresses of the local
   interfaces, then forward the message to IP destination address and
   return.

   Parse the sequence of objects in the message.  If any required
   objects are missing or the length field of the common header does not
   match an object boundary, discard the message and return.



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   Verify the INTEGRITY object, if any.  If the check fails, discard the
   message and return.

   Verify the consistent use of port fields.  If the DstPort in the
   SESSION object is zero but the SrcPort in a SENDER_TEMPLATE or
   FILTER_SPEC object is non-zero, then the message has a "conflicting
   source port" error; silently discard the message and return.

   Processing of POLICY_DATA objects will be specified in the future.

   Further processing depends upon message type.

   PATH MESSAGE ARRIVES

   Assume the PATH message arrives on interface InIf.

   Process the sender descriptor object sequence in the message as
   follows.  The Path_Refresh_Needed and Resv_Refresh_Needed flags are
   initially off.

   o    Search for a path state block (PSB) whose (session,
        sender_template) pair matches the corresponding objects in the
        message, and whose IncInterface matches InIf.

             During this search:

             1.   If a PSB is found whose session matches the
                  DestAddress and Protocol Id fields of the received
                  SESSION object, but the DstPorts differ and one is
                  zero, then build and send a "Conflicting Dst Port"
                  PERR message, drop the PATH message, and return.

             2.   If a PSB is found with a matching sender host but the
                  Src Ports differ and one of the SrcPorts is zero, then
                  build and send an "Ambiguous Path" PERR message, drop
                  the PATH message, and return.

             3.   If a forwarding PSB is found, i.e., a PSB that matches
                  the (session, sender_template) pair and whose
                  Local_Only flag is off, save a pointer to it in the
                  variable fPSB.  If none is found, set fPSB to NULL.

        o    If there was no matching PSB, then:

             1.   Create a new PSB.

             2.   Copy contents of the SESSION, SENDER_TEMPLATE,
                  SENDER_TSPEC, and PHOP (IP address and LIH) objects



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                  into the PSB.

             3.   If the sender is from the local API, set
                  OutInterface_List to the single interface whose
                  address matches the sender address, and make
                  IncInterface undefined.  Otherwise, turn on the
                  Local_Only flag.

             4.   Turn on the Path_Refresh_Needed flag.

        o    Otherwise (there is a matching PSB):

             -    If the PHOP IP address, the LIH, or Sender_Tspec
                  differs between the message and the PSB, copy the new
                  value into the PSB and turn on the Path_Refresh_Needed
                  flag.  If the PHOP IP address or the LIH differ, also
                  turn on the Resv_Refresh_Needed flag.

        o    Call the resulting PSB the "current PSB" (cPSB).  Update
             the cPSB, as follows:

             -    Start or Restart the cleanup timer for the PSB.

             -    If the message contains an ADSPEC object, copy it into
                  the PSB.

             -    Copy E_Police flag from SESSION object into PSB.

             -    Store the received TTL into the PSB.
                  If the received TTL differs from Send_TTL in the RSVP
                  common header, set the Non_RSVP flag on in the PSB.

        o    If the PSB is new or if there is no route change
             notification in place, then perform the following routing
             manipulations, but not if the cPSB is from the local API.

             1.   Invoke the appropriate Route_Query routine using
                  DestAddress from SESSION and (for multicast routing)
                  SrcAddress from Sender_Template.

                  Call the results (Rt_OutL, Rt_InIf).

             2.   If the destination is multicast and Rt_InIf differs
                  from IncInterface in the cPSB, but fPSB points to the
                  cPSB, then do the following.

                  -    Turn on the Local_Only flag and clear the
                       OutInterface_list of the fPSB.  Set the fPSB



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                       pointer to NULL.

                  -    Search for a PSB for the same (session,
                       sender_template) pair whose IncInterface matches
                       Rt_InIf.  If one is found, set fPSB to point to
                       it.

             3.   If the destination is multicast and Rt_InIf is the
                  same as IncInterface in the cPSB, but fPSB does not
                  point to the cPSB, then do the following.

                  -    Copy into the cPSB the OutInterface_list from the
                       PSB, if any, pointed to by fPSB.  Clear
                       OutInterface_list and turn on the Local_Only flag
                       in the PSB pointed to by fPSB, if any.

                  -    Turn off the Local_Only flag in the cPSB and set
                       fPSB to point to cPSB.

             4.   If Rt_OutL differs from OutInterface_list of the PSB
                  pointed to by fPSB, then:

                  -    Update the OutInterface_list of the PSB from
                       Rt_OutL, and then execute the PATH LOCAL REPAIR
                       event sequence below.

        o    If the Path_Refresh_Needed flag is now off, drop the PATH
             message and return.

             Otherwise (the path state is new or modified), do
             refreshes, upcalls, and state updates as follows.

             1.   If this PATH message came from a network interface and
                  not from a local application, make a Path Event upcall
                  for each local application for this session:

                       Call: <Upcall_Proc>( session-id, PATH_EVENT,
                                    flags, sender_tspec, sender_template
                                    [ , ADSPEC] [ , POLICY_DATA] )

             2.   If OutInterface_list is not empty, execute the PATH
                  REFRESH event sequence (below) for the sender defined
                  by the PSB.

             3.   Search for any matching reservation state, i.e., an
                  RSB whose Filter_spec_list includes a FILTER_SPEC
                  matching the SENDER_TEMPLATE and whose OI appears in
                  the OutInterface_list, and make this the `active RSB'.



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                  If none is found, drop the PATH message and return.

             4.   Execute the RESV REFRESH sequence (below) for the PHOP
                  in the PSB.

             5.   Execute the event sequence UPDATE TRAFFIC CONTROL to
                  update the local traffic control state if necessary.
                  This sequence will turn on the Resv_Refresh_Needed
                  flag if the traffic control state has been modified in
                  a manner that should trigger a reservation refresh.
                  If so, execute the RESV REFRESH sequence for the PHOP
                  in the PSB.

        o    Drop the PATH message and return.

   PTEAR MESSAGE ARRIVES

        o    Search for a PSB whose (Session, Sender_Template) pair
             matches the corresponding objects in the message.  If no
             matching PSB is found, drop the PTEAR message and return.

        o    Forward a copy of the PTEAR message to each outgoing
             interface listed in OutInterface_list of the PSB.

        o    Find each RSB that matches this PSB, i.e., whose
             Filter_spec_list matches Sender_Template in the PSB and
             whose OI is included in OutInterface_list.

             1.   If the RSB style is explicit, then:
                  -    Delete from Filter_spec_list the FILTER_SPEC that
                       matches the PSB.

                  -    if Filter_spec_list is now empty, delete the RSB.

             2.   Otherwise (RSB style is wildcard) then:

                  -    If this RSB matches no other PSB, then delete the
                       RSB.

             3.   If an RSB was found, execute the event sequence UPDATE
                  TRAFFIC CONTROL (below) to update the traffic control
                  state to be consistent with the current reservation
                  and path state.

        o    Delete the PSB.

        o    Drop the PTEAR message and return.




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   PERR MESSAGE ARRIVES

        o    Search for a PSB whose (SESSION, SENDER_TEMPLATE) pair
             matches the corresponding objects in the message.  If no
             matching PSB is found, drop the PERR message and return.

        o    If the previous hop address in the PSB is the local API,
             make an error upcall to the application:

                  Call: <Upcall_Proc>( session-id, PATH_ERROR,
                                 Error_code, Error_value, Node_Addr,
                                 Sender_Template [ , Policy_Data] )

             Any SENDER_TSPEC or ADSPEC object in the message is
             ignored.

             Otherwise, send a copy of the PERR message to the PHOP IP
             address.

        o    Drop the PERR message and return.

   RESV MESSAGE ARRIVES

        Initially, Refresh_PHOP_list is empty and the
        Resv_Refresh_Needed and NeworMod flags are off.  These variables
        are used to control immediate reservation refreshes.

        o    Determine the Outgoing Interface OI

             The logical outgoing interface OI is taken from the LIH in
             the NHOP object.  (If the physical interface is not implied
             by the LIH, it can be learned from the interface matching
             the IP destination address).

        o    Check the path state

             1.   If there are no existing PSB's for SESSION then build
                  and send a RERR message (as described later)
                  specifying "No path information", drop the RESV
                  message, and return.

             2.   If a PSB is found with a matching sender host but the
                  SrcPorts differ and one of the SrcPorts is zero, then
                  build and send an "Ambiguous Path" PERR message, drop
                  the RESV message, and return.






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        o    Check for incompatible styles.

             If any existing RSB for the session has a style that is
             incompatible with the style of the message, build and send
             a RERR message specifying "Conflicting Style", drop the
             RESV message, and return.

        Process the flow descriptor list to make reservations, as
        follows, depending upon the style.  The following uses a filter
        spec list struct Filtss of type FILTER_SPEC* (defined earlier).

        For FF style: execute the following steps independently for each
        flow descriptor in the message, i.e., for each (FLOWSPEC,
        Filtss) pair.  Here the structure Filtss consists of the
        FILTER_SPEC from the flow descriptor.

        For SE style, execute the following steps once for (FLOWSPEC,
        Filtss), with Filtss consisting of the list of FILTER_SPEC
        objects from the flow descriptor.

        For WF style, execute the following steps once for (FLOWSPEC,
        Filtss), with Filtss an empty list.

        o    Check the path state, as follows.

             1.   Locate the set of PSBs (senders) that route to OI and
                  whose SENDER_TEMPLATEs match a FILTER_SPEC in Filtss.

                  If this set is empty, build and send an error message
                  specifying "No sender information", and continue with
                  the next flow descriptor in the RESV message.

             2.   If the style has explicit sender selection (e.g., FF
                  or SE) and if any FILTER_SPEC included in Filtss
                  matches more than one PSB, build and send a RERR
                  message specifying "Ambiguous filter spec" and
                  continue with the next flow descriptor in the RESV
                  message.

             3.   If the style is SE and if some FILTER_SPEC included in
                  Filtss matches no PSB, delete that FILTER_SPEC from
                  Filtss.

             4.   Add the PHOP from the PSB to Refresh_PHOP_list, if the
                  PHOP is not already on the list.






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        o    Find or create a reservation state block (RSB) for
             (SESSION, NHOP).  If the style is distinct, Filtss is also
             used in the selection.  Call this the "active RSB".

        o    If the active RSB is new:

             1.   Set the session, NHOP, OI and style of the RSB from
                  the message.

             2.   Copy Filtss into the Filter_spec_list of the RSB.

             3.   Copy the FLOWSPEC and any SCOPE object from the
                  message into the RSB.

             4.   Set NeworMod flag on.

        o    If the active RSB is not new, check whether Filtss from the
             message contains FILTER_SPECs that are not in the RSB; if
             so, add the new FILTER_SPECs and turn on the NeworMod flag.

        o    Start or restart the cleanup timer on the active RSB, or,
             in the case of SE style, on each FILTER_SPEC of the RSB
             that also appears in Filtss.

        o    If the active RSB is not new, check whether STYLE, FLOWSPEC
             or SCOPE objects have changed; if so, copy changed object
             into RSB and turn on the NeworMod flag.

        o    If the message contained a RESV_CONFIRM object, copy it
             into the RSB and turn on NeworMod flag.

        o    If the NeworMod flag is off, continue with the next flow
             descriptor in the RESV message, if any.

        o    Otherwise (the NeworMod flag is on, i.e., the active RSB is
             new or modified), execute the UPDATE TRAFFIC CONTROL event
             sequence (below).  If the result is to modify the traffic
             control state, this sequence will turn on the
             Resv_Refresh_Needed flag and make a RESV_EVENT upcall to
             any local application.

             If the UPDATE TRAFFIC CONTROL sequence fails with an error,
             then delete a new RSB but restore the original reservation
             in an old RSB.

        o    Continue with the next flow descriptor.





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        o    When all flow descriptors have been processed, check the
             Resv_Refresh_Needed flag.  If it is now on, execute the
             RESV REFRESH sequence (below) for each PHOP in
             Refresh_PHOP_list.

        o    Drop the RESV message and return.

             If processing a RESV message finds an error, a RERR message
             is created containing flow descriptor and an ERRORS object.
             The Error Node field of the ERRORS object is set to the IP
             address of OI, and the message is sent unicast to NHOP.

   RTEAR MESSAGE ARRIVES

        Processing of a RTEAR message roughly parallels the processing
        of the corresponding RESV message

        A RTEAR message arrives with an IP destination address matching
        outgoing interface OI.  Flag Resv_Refresh_Needed is initially
        off and Refresh_PHOP_list is empty.

        o    Determine the Outgoing Interface OI

             The logical outgoing interface OI is taken from the LIH in
             the NHOP object.  (If the physical interface is not implied
             by the LIH, it can be learned from the interface matching
             the IP destination address).

        o    Process the flow descriptor list in the RTEAR message to
             tear down local reservation state, as follows, depending
             upon the style.  The following uses a filter spec list
             struct Filtss of type FILTER_SPEC* (defined earlier).

             For FF style: execute the following steps independently for
             each flow descriptor in the message, i.e., for each
             (FLOWSPEC, Filtss) pair.  Here the structure Filtss
             consists of the FILTER_SPEC from the flow descriptor.

             For SE style, execute the following steps once for
             (FLOWSPEC, Filtss), with Filtss consisting of the list of
             FILTER_SPEC objects from the flow descriptor.

             For WF style, execute the following steps once for
             (FLOWSPEC, Filtss), with Filtss an empty list.







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             1.   Find an RSB matching (SESSION, NHOP).  If the style is
                  distinct, Filtss is also used in the selection.  Call
                  this the "active RSB".  If no active RSB is found,
                  continue with next flow descriptor.

             2.   Check the style

                  If the active RSB has a style that is incompatible
                  with the style of the message, drop the RTEAR message
                  and return.

             3.   Delete from the active RSB each FILTER_SPEC that
                  matches a FILTER_SPEC in Filtss.

             4.   If all FILTER_SPECs have now been deleted from the
                  active RSB, delete the active RSB.

             5.   Execute the UPDATE TRAFFIC CONTROL event sequence
                  (below) to update the traffic control state to be
                  consistent with the reservation state.  If the result
                  is to modify the traffic control state, the
                  Resv_Refresh_Needed flag will be turned on and a
                  RESV_EVENT upcall will be made to any local
                  application.

             6.   Continue with the next flow descriptor.

        o    All flow descriptors have been processed.

             Build and send any RTEAR messages to be forwarded, in the
             following manner.

             1.   Select each PSB that routes to the outgoing interface
                  OI, and, for distinct style, that has a
                  SENDER_TEMPLATE matching Filtss.

             2.   Select a flow descriptor (Qj,Fj) (where Fj may be a
                  list) in the RTEAR message whose FILTER_SPEC matches
                  the SENDER_TEMPLATE in the PSB.  If not match is
                  found, return for next PSB.

                  -    Search for an RSB (for any outgoing interface) to
                       which the PSB routes and whose Filter_spec_list
                       includes the SENDER_TEMPLATE from the PSB.

                  -    If an RSB is found, add the PHOP of the PSB to
                       the Refresh_PHOP_list.




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                  -    Otherwise (no RSB is found), add the flow
                       descriptor (Qj,Fj) to the new RTEAR message being
                       built, in a manner appropriate to the style.

                  -    Continue with the next PSB.

             3.   If the next PSB is for a different PHOP or the last
                  PSB has been processed, forward any RTEAR message that
                  has been built.

        o    If any PSB's were found in the preceding step, and if the
             Resv_Refresh_Needed flag is now on, execute the RESV
             REFRESH sequence (below) for each PHOP in
             Refresh_PHOP_list.

        o    Drop the RTEAR message and return.

   RERR MESSAGE ARRIVES

        A RERR message arrives through the (real) incoming interface
        In_If.

        o    If there is no path state for SESSION, drop the RERR
             message and return.

        o    If the Error Code = 01 (Admission Control failure), do
             special processing as follows:

             1.   Find or create a Blockade State Block (BSB), in the
                  following style-dependent manner.

                  For WF (wildcard) style, there will be one BSB per
                  (session, PHOP) pair.

                  For FF style, there will be one BSB per (session,
                  filter_spec) pair.  Note that an FF style RERR message
                  carries only one flow descriptor.

                  For SE style, there will be one BSB per (session,
                  filter_spec), for each filter_spec contained in the
                  filter spec list of the flow descriptor.

             2.   For each BSB in the preceding step, set (or replace)
                  its FLOWSPEC Qb with FLOWSPEC from the message, and
                  set (or reset) its timer Tb to Kb*R seconds.  If the
                  BSB is new, set its PHOP value, and set its
                  Sender_Template equal to the appropriate filter_spec
                  from the message.



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             3.   Execute the RESV REFRESH event sequence (shown below)
                  for the previous hop PHOP, but only with the B_Merge
                  flag off.  That is, if processing in the RESV REFRESH
                  sequence reaches the point of turning the B_Merge flag
                  on (because all matching reservations are blockaded),
                  do not turn it on but instead exit the REFRESH
                  sequence and return here.

        o    Execute the following for each RSB for this session whose
             OI differs from In_If and whose Filter_spec_list has at
             least one filter spec in common with the FILTER_SPEC* in
             the RERR message.   For WF style, empty FILTER_SPEC*
             structures are assumed to match.

             1.   If Error_Code = 01 and the InPlace flag in the
                  ERROR_SPEC is 1 and one or more of the BSB's
                  found/created above has a Qb that is strictly greater
                  than Flowspec in the RSB, then continue with the next
                  matching RSB, if any.

             2.   If NHOP in the RSB is the local API, then:

                  -    If the FLOWSPEC in the RERR message is strictly
                       greater than the RSB Flowspec, then turn on the
                       NotGuilty flag in the ERROR_SPEC.

                  -    Deliver an error upcall to application:

                        Call: <Upcall_Proc>( session-id, RESV_ERROR,
                                        Error_code, Error_value,
                                           Node_Addr,  Error_flags,
                                           Flowspec, Filter_Spec_List
                                            [ , Policy_data] )

                       and continue with the next RSB.

             3.   If the style has wildcard sender selection, use the
                  SCOPE object SC.In from the RERR message to construct
                  a SCOPE object SC.Out to be forwarded.  SC.Out should
                  contain those sender addresses that appeared in SC.In
                  and that route to OI, as determined by scanning the
                  PSB's.  If SC.Out is empty, continue with the next
                  RSB.

             4.   Create a new RERR message containing the error flow
                  descriptor and send to the NHOP address specified by
                  the RSB.  Include SC.Out if the style has wildcard
                  sender selection.



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             5.   Continue with the next RSB.

        o    Drop the RERR message and return.

   RESV CONFIRM ARRIVES

        o    If the (unicast) IP address found in the RESV_CONFIRM
             object in the RACK message matches an interface of the
             node, a confirmation upcall is made to the matching
             application:

                  Call: <Upcall_Proc>( session-id, RESV_CONFIRM,
                              Error_code, Error_value, Node_Addr,
                                  LUB-Used, nlist, Flowspec,
                                  Filter_Spec_List, NULL, NULL )

        o    Otherwise, forward the RACK message to the IP address in
             its RESV_CONFIRM object.

        Drop the RACK message and return.

   UPDATE TRAFFIC CONTROL

        The sequence is invoked by many of the message arrival sequences
        to set or adjust the local traffic control state in accordance
        with the current reservation and path state.  An implicit
        parameter of this sequence is the `active' RSB.

        If the result is to modify the traffic control state, this
        sequence notifies any matching local applications with a
        RESV_EVENT upcall.  If the state change is such that it should
        trigger immediate RESV refresh messages, it also turns on the
        Resv_Refresh_Needed flag.

        o    Compute the traffic control parameters using the following
             steps.

             1.   Initially the local flag Is_Biggest is off.

             2.   Consider the set of RSB's matching SESSION and OI from
                  the active RSB.  If the style of the active RSB is
                  distinct, then the Filter_spec_list must also be
                  matched.

                  -    Compute the effective kernel flowspec,
                       TC_Flowspec, as the LUB of the FLOWSPEC values in
                       these RSB's.




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                  -    Compute the effective traffic control filter spec
                       (list) TC_Filter_Spec* as the union of the
                       Filter_spec_lists from these RSB's.

                  -    If the active RSB has a FLOWSPEC larger than all
                       the others, turn on the Is_Biggest flag.

             3.   Scan all RSB's matching session and Filtss, for all
                  OI.  Set TC_B_Police_flag on if TC_Flowspec is smaller
                  than, or incomparable to, any FLOWSPEC in those RSB's.

             4.   Locate the set of PSBs (senders) whose
                  SENDER_TEMPLATEs match Filter_spec_list in the active
                  RSB and whose OutInterface_list includes OI.

             5.   Set TC_E_Police_flag on if any of these PSBs have
                  their E_Police flag on.  Set TC_M_Police_flag on if it
                  is a shared style and there is more than one PSB in
                  the set.

             6.   Compute Path_Te as the sum of the SENDER_TSPEC objects
                  in this set of PSBs.

        o    Search for a TCSB matching SESSION and OI; for distinct
             style (FF), it must also match Filter_spec_list.

             If none is found, create a new TCSB.

        o    If TCSB is new:

             1.   Store TC_Flowspec, TC_Filter_Spec*, Path_Te, and the
                  police flags into TCSB.

             2.   Turn the Resv_Refresh_Needed flag on and make the
                  traffic control call:

                 TC_AddFlowspec( OI, TC_Flowspec,
                              Path_Te, police_flags)
                               ->  Rhandle, Fwd_Flowspec

             3.   If this call fails, build and send a RERR message
                  specifying "Admission control failed" and with the
                  InPlace flag off.  Delete the TCSB, delete any
                  RESV_CONFIRM object from the active RSB, and return.







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             4.   Otherwise (call succeeds), record Rhandle and
                  Fwd_Flowspec in the TCSB.  For each filter_spec F in
                  TC_Filter_Spec*, call:

                 TC_AddFilter( OI, Rhandle, Session, F)
                                     -> Fhandle

             and record the returned Fhandle in the TCSB.

        o    Otherwise, if TCSB is not new but no effective kernel
             flowspec TC_Flowspec was computed earlier, then:

             1.   Turn on the Resv_Refresh_Needed flag.

             2.   Call traffic control to delete the reservation:

                 TC_DelFlowspec( OI, Rhandle )

             3.   Delete the TCSB and return.

        o    Otherwise, if TCSB is not new but the TC_Flowspec, Path_Te,
             and/or police flags just computed differ from corresponding
             values in the TCSB, then:

             1.   If the TC_Flowspec and/or Path_Te values differ, turn
                  the Resv_Refresh_Needed flag on.

             2.   Call traffic control to modify the reservation:

                 TC_ModFlowspec( OI, Rhandle, TC_Flowspec,
                                Path_Te, police_flags )
                                     -> Fwd_Flowspec

             3.   If this call fails, build and send a RERR message
                  specifying "Admission control failed" and with the
                  InPlace bit on.  Delete any RESV_CONFIRM object from
                  the active RSB and return.

             4.   Otherwise (the call succeeds), update the TCSB with
                  the new values and save Fwd_Flowspec in the TCSB.

        o    If the TCSB is not new but the TC_Filter_Spec* just
             computed differs from the FILTER_SPEC* in the TCSB, then:

             1.   Make an appropriate set of TC_DelFilter and
                  TC_AddFilter calls to transform the Filter_spec_list
                  in the TCSB into the new TC_Filter_Spec*.




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             2.   Turn on the Resv_Refresh_Needed flag.

        o    If the active RSB contains a RESV_CONFIRM object, then:

             1.   If the Is_Biggest flag is on, move the RESV_CONFIRM
                  object into the TCSB and turn on the
                  Resv_Refresh_Needed flag. (This will later cause the
                  RESV REFRESH sequence to be invoked, which will either
                  forward or return the RESV_CONFIRM object, deleting it
                  from the TCSB in either case).

             2.   Otherwise, create and send a RACK message to the
                  address in the RESV_CONFIRM object.  Include the
                  RESV_CONFIRM object in the RACK message.  The RACK
                  message should also include an ERROR_SPEC object whose
                  Error_Node parameter is IP address of OI from the TCSB
                  and that specifies "No Error".

        o    If the Resv_Refresh_Needed flag is on and the RSB is not
             from the API, make a RESV_EVENT upcall to any matching
             application:

                  Call: <Upcall_Proc>( session-id, RESV_EVENT,
                              style, Flowspec, Filter_spec_list [ ,
                              POLICY_DATA] )

             where Flowspec and Filter_spec_list come from the TCSB and
             the style comes from the active RSB.

        o    Return to the event sequence that invoked this one.

   PATH REFRESH

        This sequence sends a path refresh for a particular sender,
        i.e., a PSB.  This sequence may be entered by either the
        expiration of a refresh timer or directly as the result of the
        Path_Refresh_Needed flag being turned on during the processing
        of a received PATH message.

        o    Insert TIME_VALUES object into the PATH message being
             built.  Compute the IP TTL for the PATH message as one less
             than the TTL value received in the message.  However, if
             the result is zero, return without sending the PATH
             message.

        o    Create a sender descriptor containing the SENDER_TEMPLATE,
             SENDER_TSPEC, and POLICY_DATA objects, if present in the
             PSB, and pack it into the PATH message being built.



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        o    Send a copy of the PATH message to each interface OI in
             OutInterface_list.  Before sending each copy:

             1.   If the PSB has the E_Police flag on and if interface
                  OI is not capable of policing, turn the E_Police flag
                  on in the PATH message being built.

             2.   Pass the ADSPEC object and Non_RSVP flag present in
                  the PSB to the traffic control call TC_Advertise.
                  Insert the modified ADSPEC object that is returned
                  into the PATH message being built.

             3.   Insert into its PHOP object the interface address and
                  the LIH for the interface.

   RESV REFRESH

        This sequence sends a reservation refresh towards a particular
        previous hop with IP address PH.  This sequence may be entered
        by the expiration of a refresh timer, or invoked from the PATH
        MESSAGE ARRIVES, RESV MESSAGE ARRIVES, RTEAR MESSAGE ARRIVES, or
        RERR MESSAGE ARRIVES sequence.

        In general, this sequence considers each of the PSB's with PHOP
        address PH.  For a given PSB, it scans the TCSBs for matching
        reservations and merges the styles, FLOWSPECs and
        Filter_spec_list's appropriately.  It then builds a RESV message
        and sends it to PH.  The details depend upon the attributes of
        the style(s) included in the reservations.

        Initially the Need_Scope flag is off and the new_SCOPE object is
        empty.

        o    Create an output message containing INTEGRITY (if
             configured), SESSION, RSVP_HOP, and TIME_VALUES objects.

        o    Determine the style for these reservations from the first
             RSB for the session, and move the STYLE object into the
             proto-message.  (Note that the present set of styles are
             never themselves merged; if future styles can be merged,
             these rules will become more complex).

        o    If style is wildcard and if there are PSB's from more than
             one PHOP and if the multicast routing protocol does not use
             shared trees, set the Need_Scope flag on.






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        o    Select each sender PSB whose PHOP has address PH.  Set the
             local flag B_Merge off and execute the following steps.

             1.   Select all TCSB's whose Filter_spec_list's match the
                  SENDER_TEMPLATE object in the PSB and whose OI appears
                  in the OutInterface_list of the PSB.

             2.   If the PSB is from the API, then:

                  -    If TCSB contains a CONFIRM object, then create
                       and send a RACK message containing the object and
                       delete the CONFIRM object from the TCSB.

                  -    Continue with next PSB.

             3.   If B_Merge flag is off then ignore a blockaded TCSB,
                  as follows.

                  -    Select BSB's that match this TCSB.  If a selected
                       BSB is expired, delete it.  If any of the
                       unexpired BSB's has a Qb that is not strictly
                       larger than TC_Flowspec, then continue processing
                       with the next TCSB.

                  However, if steps 1 and 2 result in finding that all
                  TCSB's matching this PSB are blockaded, then:

                  -    If this RESV REFRESH sequence was invoked from
                       RESV ERROR RECEIVED, then return to the latter.

                  -    Otherwise, turn on the B_Merge flag and restart
                       at step 1, immediately above.

             4.   Merge the flowspecs from this set of TCSB's, as
                  follows:

                  -    If B_Merge flag is off, compute the LUB over the
                       flowspec objects.  From each TCSB, use the
                       Fwd_Flowspec object if present, else use the
                       normal Flowspec object.











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                       While computing the LUB, check for a RESV_CONFIRM
                       object in each TCSB.  If a RESV_CONFIRM object is
                       found:

                       -    If the flowspec (Fwd_Flowspec or Flowspec)
                            in that TCSB is larger than all other (non-
                            blockaded) flowspecs being compared, then
                            save this RESV_CONFIRM object for forwarding
                            and delete from the TCSB.

                       -    Otherwise (the corresponding flowspec is not
                            the largest), create and send a RACK message
                            to the address in the RESV_CONFIRM object.
                            Include the RESV_CONFIRM object in the RACK
                            message.  The RACK message should also
                            include an ERROR_SPEC object whose
                            Error_Node parameter is IP address of OI
                            from the TCSB and specifying "No Error".

                       -    Delete the RESV_CONFIRM object from the
                            TCSB.

                  -    Otherwise (B_Merge flag is on), compute the GLB
                       over the Flowspec objects of this set of TCSB's.

                  While computing the GLB, delete any RESV_CONFIRM
                  object object in any of these TCSB's.

             5.   (All matching TCSB's have been processed).  The next
                  step depends upon the style attributes.

                  Distinct reservation (FF) style

                       Use the Sender_Template as the merged
                       FILTER_SPEC.  Pack the merged (FLOWSPEC,
                       FILTER_SPEC, F_POLICY_DATA) triplet into the
                       message as a flow descriptor.

                  Shared wildcard reservation (WF) style

                       There is no merged FILTER_SPEC.  Merge (compute
                       the LUB of) the merged FLOWSPECS from the TCSB's,
                       across all PSB's for PH.








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                  Shared distinct reservation (SE) style

                       Using the Sender_Template as the merged
                       FILTER_SPEC, form the union of the FILTER_SPECS
                       obtained from the TCSB's.  Merge (compute the LUB
                       of) the merged FLOWSPECS from the TCSB's, across
                       all PSB's for PH.

             6.   If the Need_Scope flag is on and the sender specified
                  by the PSB is not the local API:

                  -    Find each RSB that matches this PSB, i.e., whose
                       Filter_spec_list matches Sender_Template in the
                       PSB and whose OI is included in
                       OutInterface_list.

                  -    If the RSB either has no SCOPE list or its SCOPE
                       list includes the sender IP address from the PSB,
                       insert the sender IP address into new_SCOPE.

        o    (All PSB's for PH have been processed).  Finish the RESV
             message.

             1.   If Need_Scope flag is on but new_SCOPE is empty, no
                  RESV message should be sent; return.  Otherwise, if
                  Need_Scope is on, move new_SCOPE into the message.

             2.   If a shared reservation style is being built, move the
                  final merged FLOWSPEC object and filter spec list into
                  the message.

             3.   If a RESV_CONFIRM object was saved earlier, move it
                  into the new RESV message.

             4.   Set the RSVP_HOP object in the message to contain the
                  IncInterface address through which it will be sent and
                  the LIH from (one of) the PSB's.

        o    Send the message to the address PH.

   ROUTE CHANGE NOTIFICATION

        This sequence is triggered when routing sends a route change
        notification to RSVP.

        o    Each PSB is located whose SESSION matches the destination
             address and whose SENDER_TEMPLATE matches the source
             address (for multicast).



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             1.   If the OutInterface_list from the notification differs
                  from that in the PSB, execute the PATH LOCAL REPAIR
                  sequence.

             2.   If the IncInterface from the notification differs from
                  that in the PSB, update the PSB.

   PATH LOCAL REPAIR

        The sequence is entered to effect local repair after a route
        change for a given PSB.

        o    Wait for a delay time of W seconds.

        o    Execute the PATH REFRESH event sequence (above) for the
             PSB.

References

   [Baker96]  Baker, F., "RSVP Cryptographic Authentication", Work in
        Progress.


   [RFC 2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and
        S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
        FunctionalSpecification", RFC 2205, September 1997.

   [RFC 2207]  Berger, L. and T. O'Malley, "RSVP Extensions for IPSEC
        IPv4 Data Flows", RFC 2207, September 1997.

   [RSVP93]  Zhang, L., Deering, S., Estrin, D., Shenker, S., and D.
        Zappala, "RSVP: A New Resource ReSerVation Protocol", IEEE
        Network, September 1993.

Security Considerations

   Processing the RSVP INTEGRITY object [Baker96] is only mentioned in
   this memo, because the processing rules are described here only in
   general terms.  The RSVP support for IPSEC [RFC 2207] will imply
   modifications that have not yet been incorporated into these
   processing rules.










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Authors' Addresses

   Bob Braden
   USC Information Sciences Institute
   4676 Admiralty Way
   Marina del Rey, CA 90292

   Phone: (310) 822-1511
   EMail: Braden@ISI.EDU


   Lixia Zhang
   UCLA Computer Science Department
   4531G Boelter Hall
   Los Angeles, CA 90095-1596 USA

   Phone: 310-825-2695
   EMail: lixia@cs.ucla.edu

































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