📄 rfc1953.txt
字号:
Network Working Group P. Newman, Ipsilon
Request for Comments: 1953 W. L. Edwards, Sprint
Category: Informational R. Hinden, Ipsilon
E. Hoffman, Ipsilon
F. Ching Liaw, Ipsilon
T. Lyon, Ipsilon
G. Minshall, Ipsilon
May 1996
Ipsilon Flow Management Protocol Specification for IPv4
Version 1.0
Status of this Memo
This document provides information for the Internet community. This
memo does not specify an Internet standard of any kind. Distribution
of this memo is unlimited.
IESG Note:
This memo documents a private protocol for IPv4-based flows. This
protocol is NOT the product of an IETF working group nor is it a
standards track document. It has not necessarily benefited from the
widespread and in depth community review that standards track
documents receive.
Abstract
The Ipsilon Flow Management Protocol (IFMP), is a protocol for
allowing a node to instruct an adjacent node to attach a layer 2
label to a specified IP flow. The label allows more efficient access
to cached routing information for that flow. The label can also
enable a node to switch further packets belonging to the specified
flow at layer 2 rather than forwarding them at layer 3.
Table of Contents
1. Introduction....................................................2
2. Flow Types......................................................2
3. IFMP Adjacency Protocol.........................................4
3.1 Packet Format.............................................4
3.2 Procedure.................................................7
4. IFMP Redirection Protocol......................................10
4.1 Redirect Message.........................................12
4.2 Reclaim Message..........................................13
4.3 Reclaim Ack Message......................................15
4.4 Label Range Message......................................16
Newman, et. al. Informational [Page 1]
RFC 1953 IFMP Specification May 1996
4.5 Error Message............................................17
References........................................................19
Security Considerations...........................................19
Authors' Addresses................................................19
1. Introduction
The Ipsilon Flow Management Protocol (IFMP), is a protocol for
instructing an adjacent node to attach a layer 2 label to a specified
IP flow. The label allows more efficient access to cached routing
information for that flow and it allows the flow to be switched
rather than routed in certain cases.
If a network node's upstream and downstream links both redirect a
flow at the node, then the node can switch the flow at the data link
layer rather than forwarding it at the network layer. The label
space is managed at the downstream end of each link and redirection
messages are sent upstream to associate a particular flow with a
given label. Each direction of transmission on a link is treated
separately.
If the flow is not refreshed by the time the lifetime field in the
redirect message expires, then the association between the flow and
the label is discarded. A flow is refreshed by sending a redirect
message, identical to the original, before the lifetime expires.
Several flow types may be specified. Each flow type specifies the
set of fields from the packet header that are used to identify a
flow. There must be an ordering amongst the different flow types
such that a most specific match operation may be performed.
A particular flow is specified by a flow identifier. The flow
identifier for that flow gives the contents of the set of fields from
the packet header as defined for the flow type to which it belongs.
This document specifies the IFMP protocol for IPv4 on a point-to-
point link. The definition of labels, and the encapsulation of
flows, are specified in a separate document for each specific data
link technology. The specification for ATM data links is given in
[ENCAP].
2. Flow Types
A flow is a sequence of packets that are sent from a particular
source to a particular (unicast or multicast) destination and that
are related in terms of their routing and any logical handling policy
they may require.
Newman, et. al. Informational [Page 2]
RFC 1953 IFMP Specification May 1996
A flow is identified by its flow identifier.
Several different flow types can be defined. The particular set of
fields from the packet header used to identify a flow constitutes the
flow type. The values of these fields, for a particular flow,
constitutes the flow identifier for that flow. The values of these
fields must be invariant in all packets belonging to the same flow at
any point in the network.
Flow types are sub- or super-sets of each other such that there is a
clear hierarchy of flow types. This permits a most specific match
operation to be performed. (If additional flow types are defined in
the future that are not fully ordered then the required behavior will
be defined.) Each flow type also specifies an encapsulation that is
to be used after a flow of this type is redirected. The
encapsulations for each flow type are specified in a separate
document for each specific data link technology. The encapsulations
for flows over ATM data links are given in [ENCAP].
Three flow types are defined in this version of the protocol:
Flow Type 0
Flow Type 0 is used to change the encapsulation of IPv4 packets
from the default encapsulation.
For Flow Type 0: Flow Type = 0 and Flow ID Length = 0.
The Flow Identifier for Flow Type 0 is null (zero length).
Flow Type 1
Flow Type 1 is designed for protocols such as UDP and TCP in which
the first four octets after the IPv4 header specify a Source Port
number and a Destination Port number.
For Flow Type 1, Flow Type = 1 and Flow ID Length = 4 (32 bit
words).
The format of the Flow Identifier for Flow Type 1 is:
Newman, et. al. Informational [Page 3]
RFC 1953 IFMP Specification May 1996
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| IHL |Type of Service| Time to Live | Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flow Type 2
For Flow Type 2, Flow Type = 2 and Flow ID Length = 3 (32 bit
words).
The format of the Flow Identifier for Flow Type 2 is:
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| IHL | Reserved | Time to Live | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Reserved fields are unused and should be set to zero by the
sender and ignored by the receiver.
3. IFMP Adjacency Protocol
The IFMP Adjacency Protocol allows a host or router to discover the
identity of a peer at the other end of a link. It is also used to
synchronize state across the link, to detect when the peer at the
other end of the link changes, and to exchange a list of IP addresses
assigned to the link.
3.1 Packet Format
All IFMP messages belonging to the Adjacency Protocol must be
encapsulated within an IPv4 packet and must be sent to the IP limited
broadcast address (255.255.255.255). 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.
Newman, et. al. Informational [Page 4]
RFC 1953 IFMP Specification May 1996
All IFMP messages belonging to the adjacency protocol 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer Identity |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer Next Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Reserved | Max Ack Intvl |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Address List ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version
The IFMP protocol version number. The current Version = 1.
Op Code
Specifies the function of the message. Four Op Codes are
defined for the IFMP Adjacency Protocol:
SYN: Op Code = 0
SYNACK: Op Code = 1
RSTACK: Op Code = 2
ACK: Op Code = 3
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
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).
Newman, et. al. Informational [Page 5]
RFC 1953 IFMP Specification May 1996
Sender Instance
For the SYN, SYNACK, and ACK messages, is the sender's
instance number for the link. The receiver uses this to
detect when the link comes back up after going down or when
the identity of the peer at the other end of the link
changes. The instance number is a 32 bit number that is
guaranteed to be unique within the recent past and to
change when the link or node comes back up after going
down. It is used in a similar manner to the initial
sequence number (ISN) in TCP [RFC 793]. Zero is not a
valid instance number. For the RSTACK message the Sender
Instance field is set to the value of the Peer Instance
field from the incoming message that caused an RSTACK
message to be generated.
Peer Instance
For the SYN, SYNACK, and ACK messages, is what the sender
believes is the peer's current instance number for the
link. If the sender of the message does not know the
peer's current instance number for the link, the sender
must set this field to zero. For the RSTACK message the
Peer Instance field is set to the value of the Sender
Instance field from the incoming message that caused an
RSTACK message to be generated.
Peer Identity
For the SYN, SYNACK, and ACK messages, is the IP address of
the peer that the sender of the message believes is at the
other end of the link. The Peer Identity is taken from the
Source IP Address of the IP header of a SYN or a SYNACK
message. If the sender of the message does not know the IP
address of the peer at the other end of the link, the
sender must set set this field to zero. For the RSTACK
message, the Peer Identity field is set to the value of the
Source Address field from the IP header of the incoming
message that caused an RSTACK message to be generated.
Peer Next Sequence Number
Gives the value of the peer's Sequence Number that the
sender of the IFMP Adjacency Protocol message expects to
arrive in the next IFMP Redirection Protocol message. If a
node is in the ESTAB state, and the value of the Peer Next
Sequence Number in an incoming ACK message is greater than
the value of the Sequence Number plus one, from the last
IFMP Redirection Protocol message transmitted out of the
port on which the incoming ACK message was received, the
link should be reset. The procedure to reset the link is
defined in section 3.2.
Newman, et. al. Informational [Page 6]
RFC 1953 IFMP Specification May 1996
Max Ack Intvl
Maximum Acknowledgement Interval is the maximum amount of
time the sender of the message will wait until transmitting
an ACK message.
Address List
A list of one or more IP addresses that are assigned to the
link by the sender of the message. The list must have at
least one entry that is identical to the Source Address in
the IP header. The contents of this list are not used by
the IFMP protocol but can be made available to the routing
protocol.
3.2 Procedure
The IFMP Adjacency Protocol is described by the rules and state
tables given in this section.
The rules and state tables use the following operations:
o The "Update Peer Verifier" operation is defined as storing the
Sender Instance and the Source IP Address from a SYN or SYNACK
message received from the peer on a particular port.
o The procedure "Reset the link" is defined as:
1. Generate a new instance number for the link
2. Delete the peer verifier (set the stored values of Sender
Instance and Source IP Address of the peer to zero)
3. Set Sequence Number and Peer Next Sequence Number to zero
4. Send a SYN message
5. Enter the SYNSENT state
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