Cisco Cisco IOS Software Release 12.0(24)S

The reliable messages extension supports dependable message delivery among neighboring routers by 
implementing an acknowledgment mechanism that consists of a MESSAGE_ID object and a 
MESSAGE_ID_ACK object. The acknowledgments can be transmitted in an ACK message or 
piggybacked in other RSVP messages.

Each RSVP message contains one MESSAGE_ID object. If the ACK_Desired flag field is set within the 
MESSAGE_ID object, then the receiver transmits a MESSAGE_ID_ACK object to the sender to confirm 
delivery.

A bundle message consists of several standard RSVP messages grouped into a single RSVP message. 

A bundle message must contain at least one submessage. A submessage can be any RSVP message type 
other than another bundle message. Submessage types include Path, PathErr, Resv, ResvTear, ResvErr, 
ResvConf, and ACK.

Bundle messages are addressed directly to the RSVP neighbor. The bundle header immediately follows 
the IP header, and there is no intermediate transport header.

When a router receives a bundle message that is not addressed to one of its local IP addresses, it forwards 
the message.

In this release, bundle messages can be received, but not sent.

MESSAGE_ID_ACK (desired flag)

Retransmit MESSAGE_ID_ACK

Retransmit MESSAGE_ID_ACK

Continue retransmission till R

m

 Refresh

Messages are missed. Increase R

rt 

by

factor of 2 for next transmission

R

rt

R

rt 

= Retransmit Time

R

m 

= Successive Refresh Messages Missed

0 seconds

Time

Normal

Refresh State

Destination Node

Originating Node

n x R

rt

where n < R

m

If an ACK for a Path or Reservation
message is received, go to normal
refresh state; for all other messages,
stop

MESSAGE_ID_ACK (successful response)

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