📄 rfc2961.txt
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4.8. Compatibility
All nodes sending messages with the Refresh-Reduction-Capable bit set
will support the MESSAGE_ID Extension. There are no backward
compatibility issues raised by the MESSAGE_ID Class with nodes that
do not set the Refresh-Reduction-Capable bit. The MESSAGE_ID Class
has an assigned value whose form is 0bbbbbbb. Per RSVP [RFC2205],
classes with values of this form must be rejected with an "Unknown
Object Class" error by nodes not supporting the class. When the
receiver of a MESSAGE_ID object does not support the class, a
corresponding error message will be generated. The generator of the
MESSAGE_ID object will see the error and then MUST re-send the
original message without the MESSAGE_ID object. In this case, the
message generator MAY still choose to retransmit messages at the
"rapid" retransmission interval. Lastly, since the MESSAGE_ID_ACK
class can only be issued in response to the MESSAGE_ID object, there
are no possible issues with this class or Ack messages. A node MAY
support the MESSAGE_ID Extension without supporting the other refresh
overhead reduction extensions.
Berger, et al. Standards Track [Page 16]
RFC 2961 RSVP Refresh Overhead Reduction Extensions April 2001
5. Summary Refresh Extension
The summary refresh extension enables the refreshing of RSVP state
without the transmission of standard Path or Resv messages. The
benefits of the described extension are that it reduces the amount of
information that must be transmitted and processed in order to
maintain RSVP state synchronization. Importantly, the described
extension preserves RSVP's ability to handle non-RSVP next hops and
to adjust to changes in routing. This extension cannot be used with
Path or Resv messages that contain any change from previously
transmitted messages, i.e., are trigger messages.
The summary refresh extension builds on the previously defined
MESSAGE_ID extension. Only state that was previously advertised in
Path and Resv messages containing MESSAGE_ID objects can be refreshed
via the summary refresh extension.
The summary refresh extension uses the objects and the ACK message
previously defined as part of the MESSAGE_ID extension, and a new
Srefresh message. The new message carries a list of
Message_Identifier fields corresponding to the Path and Resv trigger
messages that established the state. The Message_Identifier fields
are carried in one of three Srefresh related objects. The three
objects are the MESSAGE_ID LIST object, the MESSAGE_ID SRC_LIST
object, and the MESSAGE_ID MCAST_LIST object.
The MESSAGE_ID LIST object is used to refresh all Resv state, and
Path state of unicast sessions. It is made up of a list of
Message_Identifier fields that were originally advertised in
MESSAGE_ID objects. The other two objects are used to refresh Path
state of multicast sessions. A node receiving a summary refresh for
multicast path state will at times need source and group information.
These two objects provide this information. The objects differ in
the information they contain and how they are sent. Both carry
Message_Identifier fields and corresponding source IP addresses. The
MESSAGE_ID SRC_LIST is sent in messages addressed to the session's
multicast IP address. The MESSAGE_ID MCAST_LIST object adds the
group address and is sent in messages addressed to the RSVP next hop.
The MESSAGE_ID MCAST_LIST is normally used on point-to-point links.
An RSVP node receiving an Srefresh message, matches each listed
Message_Identifier field with installed Path or Resv state. All
matching state is updated as if a normal RSVP refresh message has
been received. If matching state cannot be found, then the Srefresh
message sender is notified via a refresh NACK.
Berger, et al. Standards Track [Page 17]
RFC 2961 RSVP Refresh Overhead Reduction Extensions April 2001
A refresh NACK is sent via the MESSAGE_ID_NACK object. As described
in the previous section, the rules for sending a MESSAGE_ID_NACK
object are the same as for sending a MESSAGE_ID_ACK object. This
includes sending MESSAGE_ID_NACK object both piggy-backed in
unrelated RSVP messages or in RSVP ACK messages.
5.1. MESSAGE_ID LIST, SRC_LIST and MCAST_LIST Objects
MESSAGE_ID LIST object
MESSAGE_ID_LIST Class = 25
Class = MESSAGE_ID_LIST Class, C_Type = 1
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: 8 bits
No flags are currently defined. This field MUST be zero on
transmission and ignored on receipt.
Epoch: 24 bits
The Epoch field from the MESSAGE_ID object corresponding to the
trigger message that advertised the state being refreshed.
Message_Identifier: 32 bits
The Message_Identifier field from the MESSAGE_ID object
corresponding to the trigger message that advertised the state
being refreshed. One or more Message_Identifiers may be
included.
Berger, et al. Standards Track [Page 18]
RFC 2961 RSVP Refresh Overhead Reduction Extensions April 2001
IPv4/MESSAGE_ID SRC_LIST object
Class = MESSAGE_ID_LIST Class, C_Type = 2
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source_ |
| Message_Identifier_Tuple |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source_ |
| Message_Identifier_Tuple |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where a Source_Message_Identifier_Tuple consists of:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source_IP_Address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Berger, et al. Standards Track [Page 19]
RFC 2961 RSVP Refresh Overhead Reduction Extensions April 2001
IPv6/MESSAGE_ID SRC_LIST object
Class = MESSAGE_ID_LIST Class, C_Type = 3
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6_Source_ |
| Message_Identifier_Tuple |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6_Source_ |
| Message_Identifier_Tuple |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where a IPv6 Source_Message_Identifier_Tuple consists of:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Source_IP_Address |
| (16 Bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags: 8 bits
No flags are currently defined. This field MUST be zero on
transmission and ignored on receipt.
Epoch: 24 bits
The Epoch field from the MESSAGE_ID object corresponding to the
trigger message that advertised the state being refreshed.
Berger, et al. Standards Track [Page 20]
RFC 2961 RSVP Refresh Overhead Reduction Extensions April 2001
Message_Identifier
The Message_Identifier field from the MESSAGE_ID object
corresponding to the trigger message that advertised the Path
state being refreshed. One or more Message_Identifiers may be
included. Each Message_Identifier MUST be followed by the
source IP address corresponding to the sender described in the
Path state being refreshed.
Source_IP_Address
The IP address corresponding to the sender of the Path state
being refreshed.
IPv4/MESSAGE_ID MCAST_LIST object
Class = MESSAGE_ID_LIST Class, C_Type = 4
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Epoch |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast_ |
| Message_Identifier_ |
| Tuple |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast_ |
| Message_Identifier_ |
| Tuple |
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