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o The state tables use the following Boolean terms and operators:
A The Sender Instance in the incoming message matches the
value stored from a previous message by the "Update Peer
Verifier" operation for the port on which the incoming
message is received.
B The Sender Instance and the Source IP Address in the
incoming message matches the value stored from a previous
message by the "Update Peer Verifier" operation for the
port on which the incoming message is received.
Newman, et. al. Informational [Page 7]
RFC 1953 IFMP Specification May 1996
C The Peer Instance and Peer Identity in the incoming message
matches the value of the Sender Instance and the Source IP
Address currently in use for all SYN, SYNACK, and ACK
messages transmitted out of the port on which the incoming
message was received.
"&&" Represents the logical AND operation
"||" Represents the logical OR operation
"!" Represents the logical negation (NOT) operation.
o A timer is required for the periodic generation of SYN, SYNACK,
and ACK messages. The period of the timer is unspecified but a
value of one second is suggested.
There are two independent events: the timer expires, and a packet
arrives. The processing rules for these events are:
Timer Expires: Reset Timer
If state = SYNSENT Send SYN
If state = SYNRCVD Send SYNACK
If state = ESTAB Send ACK
Packet Arrives: If incoming message is an RSTACK
If A && C && !SYNSENT
Reset the link
Else Discard the message
Else the following State Tables.
o State synchronization across a link is considered to be achieved
when a node reaches the ESTAB state.
Newman, et. al. Informational [Page 8]
RFC 1953 IFMP Specification May 1996
State Tables
State: SYNSENT
+======================================================================+
| Condition | Action | New State |
+====================+=====================================+===========+
| SYNACK && C | Update Peer Verifier; Send ACK | ESTAB |
+--------------------+-------------------------------------+-----------+
| SYNACK && !C | Send RSTACK | SYNSENT |
+--------------------+-------------------------------------+-----------+
| SYN | Update Peer Verifier; Send SYNACK | SYNRCVD |
+--------------------+-------------------------------------+-----------+
| ACK | Send RSTACK | SYNSENT |
+======================================================================+
State: SYNRCVD
+======================================================================+
| Condition | Action | New State |
+====================+=====================================+===========+
| SYNACK && C | Update Peer Verifier; Send ACK | ESTAB |
+--------------------+-------------------------------------+-----------+
| SYNACK && !C | Send RSTACK | SYNRCVD |
+--------------------+-------------------------------------+-----------+
| SYN | Update Peer Verifier; Send SYNACK | SYNRCVD |
+--------------------+-------------------------------------+-----------+
| ACK && B && C | Send ACK | ESTAB |
+--------------------+-------------------------------------+-----------+
| ACK && !(B && C) | Send RSTACK | SYNRCVD |
+======================================================================+
State: ESTAB
+=======================================================================+
| Condition | Action | New State |
+=====================+=====================================+===========+
| SYN || SYNACK | Send ACK (note 1) | ESTAB |
+---------------------+-------------------------------------+-----------+
| ACK && B && C | Send ACK (note 1) | ESTAB |
+---------------------+-------------------------------------+-----------+
| ACK && !(B && C) | Send RSTACK | ESTAB |
+=======================================================================+
Note 1: No more than one ACK should be sent within any time period of
length defined by the timer.
Newman, et. al. Informational [Page 9]
RFC 1953 IFMP Specification May 1996
4. IFMP Redirection Protocol
A sender encapsulates within an IPv4 packet all IFMP messages
belonging to the Redirection Protocol. The sender sends these
messages to the unicast IP address of the peer at the other end of
the link. The IP address of the peer is obtained from the adjacency
protocol. The Protocol field in the IP header must contain the value
101 (decimal) indicating that the IP packet contains an IFMP message.
The Time to Live (TTL) field in the IP header must be set to 1.
All IFMP Redirection Protocol messages have the following structure:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Op Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Message Body ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
The IFMP protocol version number, currently Version = 1.
Op Code
This field gives the message type. Five message types are
currently defined for the IFMP Redirection Protocol:
REDIRECT: Op Code = 4
RECLAIM: Op Code = 5
RECLAIM ACK: Op Code = 6
LABEL RANGE: Op Code = 7
ERROR: Op Code = 8
Checksum
The 16-bit one's complement of the one's complement sum of
a pseudo header of information from the IP header, and the
IFMP message itself. The pseudo header, conceptually
prefixed to the IFMP message, contains the Source Address,
the Destination Address, and the Protocol fields from the
Newman, et. al. Informational [Page 10]
RFC 1953 IFMP Specification May 1996
IPv4 header, and the total length of the IFMP message
starting with the version field (this is equivalent to the
value of the Total Length field from the IPv4 header minus
the length of the IPv4 header itself).
Sender Instance
The sender's instance number for the link from the IFMP
Adjacency Protocol.
Peer Instance
What the sender believes is the peer's current instance
number for the link from the IFMP Adjacency protocol.
Sequence Number
The sender must increment by one, modulo 2**32, for every
IFMP Redirection Protocol message sent across a link. It
allows the receiver to process IFMP Redirection Protocol
messages in order. The Sequence Number is set to zero when
a node resets the link.
Message Body
Contains a list of one or more IFMP Redirection Protocol
message elements. All of the message elements in the list
have the same message type because the Op Code field
applies to the entire IFMP message. The number of message
elements included in a single packet must not cause the
total size of the IFMP message to exceed the MTU size of
the underlying data link. Only a single message element is
permitted in a Label Range message or in an Error message.
No IFMP Redirection Protocol messages can be sent across a link until
the IFMP Adjacency Protocol has achieved state synchronization across
that link. All IFMP Redirection Protocol messages received on a link
that does not currently have state synchronization must be discarded.
For every received IFMP Redirection Protocol message the receiver
must check the Source IP Address from the IP header, the Sender
Instance, and the Peer Instance. The incoming message must be
discarded if the Sender Instance and the Source IP Address fields do
not match the values stored by the "Update Peer Verifier" operation
of the IFMP Adjacency Protocol for the port on which the message is
received. The incoming message must also be discarded if the Peer
Instance field does not match the current value for the Sender
Instance of the IFMP Adjacency Protocol.
Newman, et. al. Informational [Page 11]
RFC 1953 IFMP Specification May 1996
4.1 Redirect Message
The Redirect Message element is used to instruct an adjacent node to
attach one or more given labels to packets belonging to one or more
specified flows each for a specified period of time. The Redirect
message is not acknowledged.
Each Redirect message element has the following structure:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow Type | Flow ID Length| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Flow Identifier ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flow Type
Specifies the Flow Type of the flow identifier contained in
the Flow Identifier field.
Flow ID Length
Specifies the length of the Flow Identifier field in
integer multiples of 32 bit words.
Lifetime field
Specifies the length of time, in seconds, for which this
redirection is valid. The association of flow identifier
and label should be discarded at a time no greater than
that specified by the Lifetime field. A value of zero is
not valid.
Label field
Contains a 32 bit label. The format of the label is
dependent upon the type of physical link across which the
Redirect message is sent. (The format of the label for ATM
data links is specified in [ENCAP].)
Flow Identifier
Identifies the flow with which the specified label should
be associated. The length of the Flow Identifier field
must be an integer multiple of 32 bit words to preserve 32
bit alignment.
Newman, et. al. Informational [Page 12]
RFC 1953 IFMP Specification May 1996
A node can send an IFMP message containing one or more Redirect
message elements across a link to its upstream neighbor. Each
Redirect message element requests that the upstream neighbor
associate a given link-level label to packets belonging to a
specified flow for up to a specified period of time. A node
receiving an IFMP message that contains one or more Redirect message
elements from an adjacent downstream neighbor can choose to ignore
any or all of the Redirect message elements. Neither the IFMP
message nor any of the Redirect message elements are acknowledged.
If the node chooses to accept a particular Redirect message element
and to redirect the specified flow, it should attach the label
specified in the Redirect message element to all further packets sent
on that flow until it chooses to do so no longer, or until the
specified lifetime expires. While the flow remains redirected, the
encapsulation specified by the definition of the Flow Type given in
the Redirect message element must be used for all packets belonging
to that flow. If the label in a Redirect message element is outside
the range that can be handled across the relevant link, a Label Range
message can be returned to the sender. The Label Range message
informs the sender of the Redirect message of the range of labels
that can be sent across the link.
If a Redirect message element is received specifying a flow that is
already redirected, the Label field in the received Redirect message
element must be checked against the label stored for the redirected
flow. If they agree, the lifetime of the redirected flow is reset to
that contained in the Redirect message element. If they disagree,
the Redirect message element is ignored, and the flow returned to the
default state. There is a minimum time between Redirect message
elements specifying the same flow. The default value is one second.
If a receiving node detects an error in any of the fields of a
Redirect message element, the node must discard that message element
without affecting any other Redirect message elements in the same
IFMP message. The receiver should return an error message to the
sender only in the case that the receiver does not understand the
version of the IFMP protocol in the received IFMP message or does not
understand a Flow Type in any of the Redirect message elements. An
Error Message should be returned for each Flow Type that is not
understood.
4.2 Reclaim Message
The Reclaim message element is used by a node to instruct an adjacent
upstream node to unbind one or more flows from the labels to which
they are currently bound, and to release the labels.
Newman, et. al. Informational [Page 13]
RFC 1953 IFMP Specification May 1996
Each Reclaim message element has the following structure:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow Type | Flow ID Length| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Flow Identifier ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flow Type
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