Internet Engineering Task Force (IETF) T. Tsenov
Request for Comments: 5972 H. Tschofenig
Category: Informational Nokia Siemens Network
ISSN: 2070-1721 X. Fu, Ed.
Univ. Goettingen
C. Aoun
Consultant
E. Davies
Folly Consulting
October 2010
General Internet Signaling Transport (GIST) State Machine
Abstract
This document describes state machines for the General Internet
Signaling Transport (GIST). The states of GIST nodes for a given
flow and their transitions are presented in order to illustrate how
GIST may be implemented.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5972.
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document authors. All rights reserved.
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Tsenov, et al. Informational [Page 1]RFC 5972 GIST State Machine October 2010
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than English.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Notational Conventions Used in State Diagrams ...................3
4. State Machine Symbols ...........................................5
5. Common Rules ....................................................6
5.1. Common Procedures ..........................................7
5.2. Common Events ..............................................8
5.3. Common Variables ...........................................9
6. State Machines .................................................11
6.1. Diagram Notations .........................................12
6.2. State Machine for GIST Querying Node ......................12
6.3. State Machine for GIST Responding Node ....................16
7. Security Considerations ........................................18
8. Acknowledgments ................................................18
9. References .....................................................18
9.1. Normative References ......................................18
9.2. Informative References ....................................18
Appendix A. State Transition Tables ...............................20
A.1. State Transition Tables for GIST Querying Node ............20
A.2. State Transition Tables for GIST Responding Node ..........24
Tsenov, et al. Informational [Page 2]RFC 5972 GIST State Machine October 2010
1. Introduction
The state machines described in this document are illustrative of how
the GIST protocol defined in [1] may be implemented for the GIST
nodes in different locations of a flow path. Where there are
differences, [1] is authoritative. The state machines are
informative only. Implementations may achieve the same results using
different methods.
There are two types of possible entities for GIST signaling:
- GIST querying node: GIST node that initiates the discovery of the
next peer;
- GIST responding node: GIST node that is the discovered next peer.
We describe a set of state machines for these entities to illustrate
how GIST may be implemented.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [2].
3. Notational Conventions Used in State Diagrams
The following text is reused from [3], and the state diagrams are
based on the conventions specified in [4], Section 8.2.1. Additional
state machine details are taken from [5].
RFC 4137 [3] reproduced the following text from Section 8.2.1 of IEEE
802-1X-2004 [4].
State diagrams are used to represent the operation of the protocol
by a number of cooperating state machines, each comprising a group
of connected, mutually exclusive states. Only one state of each
machine can be active at any given time.
. . .
All permissible transitions between states are represented by
arrows, the arrowhead denoting the direction of the possible
transition. Labels attached to arrows denote the condition(s)
that must be met in order for the transition to take place. All
conditions are expressions that evaluate to TRUE or FALSE; if a
condition evaluates to TRUE, then the condition is met. The label
UCT denotes an unconditional transition (i.e., UCT always
Tsenov, et al. Informational [Page 3]RFC 5972 GIST State Machine October 2010
evaluates to TRUE). A transition that is global in nature (i.e.,
a transition that occurs from any of the possible states if the
condition attached to the arrow is met) is denoted by an open
arrow; i.e., no specific state is identified as the origin of the
transition. When the condition associated with a global
transition is met, it supersedes all other exit conditions
including UCT. The special global condition BEGIN supersedes all
other global conditions, and once asserted it remains asserted
until all state blocks have executed to the point that variable
assignments and other consequences of their execution remain
unchanged.
On entry to a state, the procedures defined for the state (if any)
are executed exactly once, in the order that they appear on the
page. Each action is deemed to be atomic; i.e., execution of a
procedure completes before the next sequential procedure starts to
execute. No procedures execute outside a state block. The
procedures in only one state block execute at a time, even if the
conditions for execution of state blocks in different state
machines are satisfied, and all procedures in an executing state
block complete execution before the transition to and execution of
any other state block occurs. That is, the execution of any state
block appears to be atomic with respect to the execution of any
other state block, and the transition condition to that state from
the previous state is TRUE when execution commences. The order of
execution of state blocks in different state machines is undefined
except as constrained by their transition conditions. A variable
that is set to a particular value in a state block retains this
value until a subsequent state block executes a procedure that
modifies the value.
On completion of all the procedures within a state, all exit
conditions for the state (including all conditions associated with
global transitions) are evaluated continuously until one of the
conditions is met. The label ELSE denotes a transition that
occurs if none of the other conditions for transitions from the
state are met (i.e., ELSE evaluates to TRUE if all other possible
exit conditions from the state evaluate to FALSE). Where two or
more exit conditions with the same level of precedence become TRUE
simultaneously, the choice as to which exit condition causes the
state transition to take place is arbitrary.
In addition to the above notation, there are a couple of
clarifications specific to this document. First, all boolean
variables are initialized to FALSE before the state machine execution
begins. Second, the following notational shorthand is specific to
this document:
Tsenov, et al. Informational [Page 4]RFC 5972 GIST State Machine October 2010
<variable> = <expression1> | <expression2> | ...
Execution of a statement of this form will result in <variable>
having a value of exactly one of the expressions. The logic for
which of those expressions gets executed is outside of the state
machine and could be environmental, configurable, or based on
another state machine such as that of the method.
4. State Machine Symbols
( )
Used to force the precedence of operators in boolean expressions
and to delimit the argument(s) of actions within state boxes.
;
Used as a terminating delimiter for actions within state boxes.
Where a state box contains multiple actions, the order of
execution follows the normal English language conventions for
reading text.
=
Assignment action. The value of the expression to the right of
the operator is assigned to the variable to the left of the
operator. Where this operator is used to define multiple
assignments, e.g., a = b = X, the action causes the value of the
expression following the right-most assignment operator to be
assigned to all of the variables that appear to the left of the
right-most assignment operator.
!
Logical NOT operator.
&&
Logical AND operator.
||
Logical OR operator.
if...then...
Conditional action. If the boolean expression following the "if"
evaluates to TRUE, then the action following the "then" is
executed.
{ statement 1, ... statement N }
Compound statement. Braces are used to group statements that are
executed together as if they were a single statement.
Tsenov, et al. Informational [Page 5]RFC 5972 GIST State Machine October 2010
!=
Inequality. Evaluates to TRUE if the expression to the left of
the operator is not equal in value to the expression to the right.
==
Equality. Evaluates to TRUE if the expression to the left of the
operator is equal in value to the expression to the right.
>
Greater than. Evaluates to TRUE if the value of the expression to
the left of the operator is greater than the value of the
expression to the right.
<=
Less than or equal to. Evaluates to TRUE if the value of the
expression to the left of the operator is either less than or
equal to the value of the expression to the right.
++
Increment the preceding integer operator by 1.
+
Arithmetic addition operator.
&
Bitwise AND operator.
5. Common Rules
Throughout the document we use terms defined in [1], such as Query,
Response, and Confirm.
The state machine represents the handling of GIST messages that match
a Message Routing State's Message Routing Information (MRI), NSIS
Signaling Layer Protocol identifier (NSLPID), and session identifier
(SID) and with no protocol errors. Separate parallel instances of
the state machines should handle messages for different Message
Routing States (MRSs).
The state machine represents the states and transitions of the
upstream and downstream peers of the Message Routing State.
For simplification, not all objects included in a message are shown.
Only those that are significant for the case are shown. State
machines do not present handling of messages that are not significant
for management of the states.
Tsenov, et al. Informational [Page 6]RFC 5972 GIST State Machine October 2010
The state machines presented in this document do not cover all
functions of a GIST node. Functionality of message forwarding,
transmission of NSLP data without MRS establishment, and providing of
the received messages to the appropriate MRS, we refer to as "lower-
level pre-processing" step. Pre-processing provides to the
appropriate MRS state machine only the messages that are matched
against waiting Query/Response cookies, or the triplet (MRI, NSLPID,
SID) of the established MRS. This is represented by "rx_*" events in
the state machines.
Management of messaging associations (MAs) is considered in the
document via procedures, events, and variables, which describe MA
interaction with the MRS state machines. A state machine for MA
management is not explicitly presented.
5.1. Common Procedures
Tx_Query:
Transmit of Query message.
Tx_Response:
Transmit of Response message.
Tx_Confirm:
Transmit of Confirm message.
Tx_Data:
Transmit of Data message.
Tg_MessageStatus:
NSLP/GIST API message informing NSLP application of unsuccessful
delivery of a message
Tg_RecvMsg:
NSLP/GIST API message that provides received message to NSLP
application.
Tg_NetworkNotification:
NSLP/GIST API message that informs NSLP application of change in
MRS.
Install downstream/upstream MRS:
Install new Message Routing State and save the corresponding peer
state info (IP address and UDP port, or pointer to the used MA)
for the current Message Routing State or update the corresponding
peer state info.
Tsenov, et al. Informational [Page 7]RFC 5972 GIST State Machine October 2010
Delete MRS:
Delete installed downstream/upstream peer's info for the current
Message Routing State, and delete the Message Routing State if
required.
Refresh MRS:
Refreshes installed MRS.
Queue NSLP info:
Save NSLP messages in a queue until conditions for their sending
are present, e.g., a required MA association is established.
CheckPeerInfo:
The sender of the received data message is matched against the
installed peer info in the MRS.
Delete MA:
Delete/disconnect used MA.
Stop using shared MA:
Stop using shared MA. If the shared MA is no longer being used by
any other MRSs, it depends on the local policy whether it is
deleted or kept.
Tg_Establish_MA:
Triggers establishment of a new MA.
Start/Restart a timer variable (Section 5.3):
Start/Restart of a certain timer.
Install/Update/Delete UpstreamPeerInfo variable (Section 5.3):
Management of upstream peer info in state machine of responding
node.
5.2. Common Events
Rx_Query:
Receive of Query message.
Rx_Response:
Receive of Response message.
Rx_Confirm:
Receive of Confirm message.
Rx_Data:
Receive of Data message.
Tsenov, et al. Informational [Page 8]RFC 5972 GIST State Machine October 2010
Tg_SendMsg:
NSLP/GIST API message from NSLP application that requests
transmission of a NSLP message.
Tg_SetStateLifetime(time_period):
NSLP/GIST API message providing info for the lifetime of a Routing
State (RS), required by the application. "Time_period = 0"
represents the cancellation of established RSs/MAs, invoked by the
NSLP application.
Tg_InvalidRoutingState:
NSLP/GIST API notification from NSLP application for path change.
Tg_ERROR:
General Error event / system level error.
Tg_MA_Established:
A new MA has been successfully established.
Tg_MA_Error:
Error event with used MA.
Timeout a timer variable (Section 5.3):
Timeout of a certain timer.
5.3. Common Variables
Variables listed in this section are defined as:
- Specific information carried in the received messages.
- Conditions that are results of processes not defined in the state
machine model.
State machine logic is based on these general conditions and message
parameters.
The type of mode and destination info is determined by NSLP
application parameters and local GIST policy. Here it is represented
by the common variables D-mode, C-mode, and MAinfo.
C-mode:
The message MUST be transmitted in C-mode. This is specified by
"Message transfer attributes" set by NSLP application to any of
the following values:
"Reliability" is set to TRUE.
Tsenov, et al. Informational [Page 9]RFC 5972 GIST State Machine October 2010
"Security" is set to values that request secure handling of a
message.
"Local processing" is set to values that require services offered
by C-mode (e.g., congestion control) [1].
D-mode:
The message MUST be transmitted in D-mode. This is specified by
local policy rules. If the "Message transfer attributes" are not
set by NSLP application to any of the following values, then:
"Reliability" is set to TRUE.
"Security" is set to values that request special security handling
of a message.
"Local processing" is set to values that require services offered
by C-mode [1].
MAinfo:
GIST message parameters describing the required MA or proposed MA,
e.g., "Stack-proposal" and "Stack-Configuration-Data" [1].
NSLPdata:
NSLP application data.
RespCookie:
Responder Cookie that is being sent by the responding node with
the Response message in case that its local policy requires a
confirmation from the querying node.
ConfirmRequired:
Indicator that a Confirm message is required by the local policy
rule for installation of a new MRS.
NewPeer:
Indicator that a Response message is received from a new
responding peer.
MAexist:
Indicator that an existing MA will be reused in data transfer
between peers.
UpstreamPeerInfo:
Upstream peer info that is saved in an established MRS.
T_Inactive_QNode:
Message Routing State lifetime timer in querying node.
Tsenov, et al. Informational [Page 10]RFC 5972 GIST State Machine October 2010
T_Expired_RNode:
Message Routing State lifetime timer in responding node.
T_Refresh_QNode:
Message Routing State refresh timer in querying node.
T_No_Response:
Timer for the waiting period for Response message in querying
node.
T_No_Confirm:
Timer for the waiting period for Confirm message in responding
node.
No_MRS_Installed:
Data sent by responding node via a Response message that indicates
loss of Confirm message.
6. State Machines
The following section presents the state machine diagrams of GIST
peers. RFC 5972 is published as a .txt file. A supplementary .pdf
is being published as well.
In the .pdf document, the state machine diagrams are depicted in
detail. All state machine information (triggering event, action
taken, and variable status) is represented in the diagrams.
In the .txt document, state machine diagrams depict only transition
numbers. Following each diagram is a list of state transition
descriptions. Complete transition details (triggering event, action
taken, and variable status) are given in state transition tables in
Appendix A.
Please use the .pdf version whenever possible. It is the clearer
representation of the state machine. In case of a difference between
the two documents, please refer to the .pdf version.
Tsenov, et al. Informational [Page 11]RFC 5972 GIST State Machine October 2010
6.1. Diagram Notations
+--------------------------------+
| STATE |
+--------------+-----------------+
|
|
ooooo
o N o Transition N
ooooo
|
v
+--------------------------------+
| STATE |
+--------------------------------+
Figure 1: Diagram notations
6.2. State Machine for GIST Querying Node
The state machine diagram of the GIST querying node is below.
Transition descriptions follow.
Please refer to Appendix A.1 for complete transition details
(triggering event, action taken, and variable status).
Tsenov, et al. Informational [Page 12]RFC 5972 GIST State Machine October 2010
+-----------+ ooooo
| Any State +----------o 18 o
+-----------+ ooooo
|
v
+-----------------------------------------------------------------+
| IDLE |
+--+--------------------------------------------------------------+
| ^ ^ ^
| | | |
ooooo ooooo ooooo ooooo ooooo | |
o 1 o o 2 o +o 3 o+ +o 4 o+ +o 5 o+ | |
ooooo ooooo | ooooo | | ooooo | | ooooo | | |
| | | | | | | | | |
v | | v | v | v | |
+-----------+-----+----------+----------+--------+ | |
| Wait Response | | |
+--+-------------------------------------+-------+ | |
| ^ | | |
| | | | |
ooooo | ooooo ooooo ooooo |
o 6 o | +o 5 o+ o 7 o o 8 o |
ooooo | | ooooo | ooooo ooooo |
| | | | | | |
| | | v v | |
| | +----+-------------------------------+---+ |
| | | Wait MA Establishment | |
| | +------------------------------+---------+ |
| | ^ | |
| | | | |
| ooooo ooooo ooooo ooooo ooooo
| o 9 o o 11 o +o 13 o+ o 12 o o 10 o
| ooooo ooooo | ooooo | ooooo ooooo
| | | | | | |
v | | | v v |
+----------+----------+--------+------------------------------+---+
| Established Downstream MRS |
+--+-----------+-----------+-----------+-----------+--------------+
| ^ | ^ | ^ | ^ | ^
| | | | | | | | | |
| ooooo | | ooooo | | ooooo | | ooooo | | ooooo |
+o 16 o+ +o 14 o+ +o 15 o+ +o 4 o+ +o 17 o+
ooooo ooooo ooooo ooooo ooooo
Figure 2: State Machine for GIST Querying Node
Tsenov, et al. Informational [Page 13]RFC 5972 GIST State Machine October 2010
1**) An initial request from the NSLP application is received, which
triggers Query messages requesting either D-mode or C-mode.
Depending on the node's local policy, the NSLP data might be
piggybacked in the Query requesting D-mode. The Query may carry
MAinfo if C-mode transport is needed.
2) T_No_Response timer expires, and the maximum number of retries
has been reached. The NSLP application is notified of the GIST
peer discovery failure.
3) T_No_Response timer expires. The Query is resent.
4) A Data message is received. It is checked to see whether its
sender matches the installed downstream peer info in the MRS; if
so, it is processed. In WaitResponse state, this event might
happen in the process of an MA upgrade, when the downstream peer
is still not aware of establishment of the new MA.
5) The NSLP application provides data for sending. NSLP data is
queued because the downstream peer is not discovered or the
required MA is still not established.
6) A Response message is received. If a D-mode connection is
requested or the available MA can be reused for the requested
C-mode, the MRS is established.
7*) Response message is received. If a C-mode connection must be
established, and there is no available MA to be reused, MA
establishment is initiated and the system waits for it to be
completed.
8) MA establishment fails. NSLP application is notified for
unsuccessful message delivery.
9) The NSLP application provides data for sending, and the
requested transport parameters require an upgrade of the
established MRS from D-mode/C-mode to C-mode. Or, the NSLP
application notifies the GIST instance of the path change. As a
result, downstream GIST peer discovery is initiated.
10) The MRS lifetime expires or the NSLP application notifies that
the MRS is no longer needed. The MRS is deleted. If not
needed, the MA is deleted, too. The NSLP application is
notified of the MRS change.
11*) The path change is detected as a Response message from a new
downstream GIST peer is received. A new MA must be established
for the requested C-mode.
Tsenov, et al. Informational [Page 14]RFC 5972 GIST State Machine October 2010
12*) A new MA is established. The MRS is installed. The queued NSLP
data is sent.
13) T_Refresh_QNode timer expires. The Query message is sent.
14) The NSLP application provides data for sending. It is sent via
Data message towards the downstream GIST peer.
15) The Response message from the downstream GIST peer is received.
The peer is not changed. The MRS is refreshed (T_Refresh_QNode
timer is restarted).
16) The path change is detected as a Response message from a new
downstream GIST peer is received. D-mode is requested, or the
existing MA can be reused for the requested C-mode.
17) The responding peer indicates that it has not received a Confirm
message and it has no established upstream MRS. The Confirm
message is resent.
18) A general error or system-level error occurs. The MRS is
deleted. If not needed, the MA is deleted, too. The NSLP
application is notified of the MRS change.
Remarks:
*) Response and Confirm messages might be sent either in D-mode or
C-mode, before or after MA establishment, depending on the node's
local three-way handshake policy and the availability of the MAs
to be reused. See [1] for details.
**) Depending on GIST local policy, NSLPdata might be sent as the
payload of Query and Confirm messages (piggybacking).
Tsenov, et al. Informational [Page 15]RFC 5972 GIST State Machine October 2010
6.3. State Machine for GIST Responding Node
The GIST responding node state machine diagram is below. Transition
descriptions follow.
Please refer to Appendix A.2 for complete transition details
(triggering event, action taken, and variable status).
+-----------+ ooooo
| Any State +----------o 14 o
+-----------+ ooooo
|
v
+-----------------------------------------------------------------+
| IDLE |
+--+-------------------------------+------------------------------+
| ^ | ^
| | | |
ooooo | ooooo ooooo ooooo
o 1 o | o 2 o +o 4 o+ o 3 o
ooooo | ooooo | ooooo | ooooo
| | | | | |
| | v | v |
| | +--------------------+---------------+---+
| | | Wait Confirm |
| | +---------+------------------+-----------+
| | | ^ | ^
| | | | | |
| ooooo ooooo ooooo ooooo | ooooo |
| +o 13 o+ o 8 o o 5 o o 7 o +o 6 o+
| | ooooo | ooooo ooooo ooooo ooooo
| | | | | |
v | v | v |
+------+-------------+------------------------+-------------------+
| Established Upstream MRS |
+------+-------------+-------------+------------+-----------------+
| ^ | ^ | ^ | ^
| | | | | | | |
| ooooo | | ooooo | | ooooo | | ooooo |
+o 9 o+ +o 11 o+ +o 12 o+ +o 10 o+
ooooo ooooo ooooo ooooo
Figure 3: State Machine for GIST Responding Node
1) A Query message is received. The MRS is installed immediately
because local policy permits it. The Query message might carry
piggybacked NSLP data that will be provided to the NSLP
application.
Tsenov, et al. Informational [Page 16]RFC 5972 GIST State Machine October 2010
2) A Query message is received. Local policy requires an explicit
Confirm message for MRS installation. The Query message might
carry piggybacked NSLP data that will be provided to the NSLP
application.
3) T_No_Confirm timer expires. Note that all cases of lost handshake
GIST messages are handled only by the GIST querying node via
resend of the Query message.
4) A Query message is received again. This means that the sent
Response message has not been received by the upstream GIST peer.
The Response message is resent.
5) A Confirm message is received that causes installation of the
upstream MRS.
6) In case of a lost Confirm message, data messages might be received
from the upstream GIST node (it is unaware of the lost Confirm
message). A Response message indicating the loss of the Confirm
is sent back to the upstream GIST node.
7) A Query message is received (from either an existing upstream GIST
node or a new upstream GIST node) with a request to change the
used GIST operation mode (from D-mode/C-mode to C-mode, if
available; otherwise, it stays the same). Local policy requires
an explicit Confirm message for MRS installation.
8) The MRS lifetime expires or the NSLP application notifies that the
MRS is no longer needed. The MRS is deleted. If used and not
needed, the MA is deleted, too. The NSLP application is notified
of the MRS change.
9) The NSLP application provides data for sending. NSLP data is sent
if the discovery process is successfully accomplished, or it is
queued if a Confirm message is still expected to confirm
establishment of an MA.
10) A Query message is received. If it is sent from a new upstream
GIST node, then there is a path change. Local policy does not
need an explicit Confirm message for MRS installation. The MRS
data is updated.
11) A Query message is received with a request to change the used
GIST operation mode (from D-mode/C-mode to C-mode, if available;
otherwise, it stays the same). Local policy does not need an
explicit Confirm message for MRS installation. The MRS data is
updated.
Tsenov, et al. Informational [Page 17]RFC 5972 GIST State Machine October 2010
12) A Data message is received. Data messages are accepted only if
the complete MRS is installed, e.g., the upstream peer info is
installed. If not, then a Confirm message is expected and the
Data message is not accepted. A Response message indicating the
loss of the Confirm is sent back to the upstream GIST node.
13) A Confirm message is received. It accomplishes assignment of an
existing MA (or establishment of a new MA) needed for data
transfer between peers. The information for the used MA is
installed as the upstream peer info.
14) A general error or system-level error occurs. The MRS is
deleted. If not needed, the MA is deleted, too. The NSLP
application is notified of the MRS change.
7. Security Considerations
This document does not raise new security considerations. Security
considerations are addressed in the GIST specification [1] and in
[6].
8. Acknowledgments
The authors would like to thank Christian Dickmann who contributed to
refining of the state machine.
The authors would like to thank Robert Hancock, Ingo Juchem, Andreas
Westermaier, Alexander Zrim, Julien Abeille Youssef Abidi, and Bernd
Schloer for their insightful comments.
9. References
9.1. Normative References
[1] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", RFC 5971, October 2010.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[3] Vollbrecht, J., Eronen, P., Petroni, N., and Y. Ohba, "State
Machines for Extensible Authentication Protocol (EAP) Peer and
Authenticator", RFC 4137, August 2005.
Tsenov, et al. Informational [Page 18]RFC 5972 GIST State Machine October 2010
[4] Institute of Electrical and Electronics Engineers, "Standard for
Local and Metropolitan Area Networks: Port-Based Network Access
Control", IEEE 802-1X-2004, December 2004.
[5] Fajardo, V., Ed., Ohba, Y., and R. Marin-Lopez, "State Machines
for the Protocol for Carrying Authentication for Network Access
(PANA)", RFC 5609, August 2009.
[6] Tschofenig, H. and D. Kroeselberg, "Security Threats for Next
Steps in Signaling (NSIS)", RFC 4081, June 2005.
Tsenov, et al. Informational [Page 19]RFC 5972 GIST State Machine October 2010
Appendix A. State Transition Tables
The state transition tables below represent the state diagrams in
ASCII format. Please use the .pdf version whenever possible. It is
the clearer representation of the state machine.
For each state there is a separate table that lists in each row:
- an event that triggers a transition,
- actions taken as a result of the incoming event,
- and the new state at which the transitions ends.
A.1. State Transition Tables for GIST Querying Node
Please refer to the state machine diagram in Figure 2.
-----------
State: IDLE
-----------
+Transition
| |Condition |Action |State
V--+------------------------+-------------------------+-----------
1) |tg_SendMsg |tx_Query |Wait
** | |start T_No_Response |Response
| |Queue NSLP data |
| | |
18)|Tg_ERROR |Delete MRS |IDLE
| |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
Tsenov, et al. Informational [Page 20]RFC 5972 GIST State Machine October 2010
-----------
State: WaitResponse
-----------
+Transition
| |Condition |Action |State
V--+------------------------+-------------------------+-----------
2) |(timeout T_No_Response) |tg_MessageStatus |IDLE
|&&(MaxRetry) | |
| | |
3) |(timeout T_No_Response) |Tx_Query |Wait
|&&(!MaxRetry) |restart T_No_Response |Response
| | |
4) |rx_Data |IF(CheckPeerInfo) |Wait
| | tg_RecvMsg to Appl.|Response
| | |
5) |tg_SendMsg |Queue NSLP data |Wait
| | |Response
| | |
6) |rx_Response)|| |Install MRS |Established
|(rx_Response(MAinfo)&& |IF (RespCookie) |Downstream
|(MAexist)) | tx_Confirm(RespCookie)|MRS
| |tx_Data(Queued NSLP data)|
| | |
7) |rx_Response(MAinfo)&& |tg_Establish_MA |Wait MA
* |(!MAexist) |(tx_Confirm) |Establish.
| | |
| | |
18)|Tg_ERROR |(Delete MRS) |IDLE
| |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
Tsenov, et al. Informational [Page 21]RFC 5972 GIST State Machine October 2010
-----------
State: Established Downstream MRS
-----------
+Transition
| |Condition |Action |State
V--+------------------------+-------------------------+-----------
4) |rx_Data |IF(CheckPeerInfo) |Established
| | tg_RecvMsg to Appl.|Downstream
| | |MRS
| | |
9) |((tg_SendMsg)&&(C-mode) |tx_Query |Wait
|&&(!MAexist))|| |Queue NSLP data |Response
|(tg_MA_error)|| | |
|(tg_InvalidRoutingState)| |
| | |
10)|(timeout T_Inactive_ |Delete MRS |IDLE
| QNode)|||IF (MA is used) |
|(tg_SetStateLifetime(0))| (Delete MA)|| |
| | (Stop using shared MA)|
| |Tg_NetworkNotification |
| | |
11)|(rx_Response(MAinfo)&& |((Delete MA)|| |Wait MA
* |(NewPeer)&&(!MA_exist)) |(Stop using shared MA)) |Establish.
| |tg_Establish_MA |
| |(tx_Confirm) |
| | |
13)|timeout T_Refresh_QNode |tx_Query |Established
| | |Downstream
| | |MRS
| | |
14)|tg_SendMsg |tx_Data |Established
| |restart T_Inactive_QNode |Downstream
| | |MRS
| | |
15)|(rx_Response)&& |Refresh MRS |Established
|(!NewPeer) |restart T_Inactive_QNode |Downstream
| | |MRS
| | |
16)|(rx_Response)|| |IF (MA is used) |Established
|(rx_Response(Mainfo)&& | (Delete MA)|| |Downstream
|(MAexist)))&&(NewPeer) | (Stop using shared MA)|MRS
| |Install MRS |
| |restart T_Inactive_QNode |
| |IF (RespCookie) |
| | tx_Confirm(RespCookie)|
| | |
Tsenov, et al. Informational [Page 22]RFC 5972 GIST State Machine October 2010
17)|rx_Response(No_MRS_ |tx_Confirm(RespCookie) |Established
| installed)|tx_Data(Queued NSLP data)|Downstream
| | |MRS
| | |
18)|Tg_ERROR |(Delete MRS) |IDLE
| |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
-----------
State: Wait MA Establishment
-----------
+Transition
| |Condition |Action |State
V--+------------------------+-------------------------+-----------
5) |tg_SendMsg |Queue NSLP data |Wait MA
| | |Establish.
| | |
8) |tg_MA_error |Delete MRS |IDLE
| |tg_MessageStatus |
| | |
12)|tg_MA_Established |Install MRS |Established
* | |(tx_Confirm) |Downstream
| |tx_Data(Queued NSLP data)|MRS
| | |
18)|Tg_ERROR |Delete MRS |IDLE
| |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
Tsenov, et al. Informational [Page 23]RFC 5972 GIST State Machine October 2010
A.2. State Transition Tables for GIST Responding Node
Please refer to the state machine diagram in Figure 3.
-----------
State: IDLE
-----------
+Transition
| |Condition |Action |State
v--+------------------------+-------------------------+-----------
1) |rx_Query&& |tx_Response |Established
|(!ConfirmRequired) |Install MRS |Upstream
| |IF(NSLPdata) |MRS
| | tg_RecvMsg(NSLPdata)|
| | to Appl.|
| | |
2) |rx_Query&& |tx_Response |Wait
|(ConfirmRequired) |start T_No_Confirm |Confirm
| |IF(NSLPdata) |
| | tg_RecvMsg(NSLPdata)|
| | to Appl.|
| | |
---+------------------------+-------------------------+-----------
-----------
State: WAIT CONFIRM
-----------
+Transition
| |Condition |Action |State
v--+------------------------+-------------------------+-----------
3) |timeout T_No_Confirm | |IDLE
| | |
4) |rx_Query&& |tx_Response |Wait
|(ConfirmRequired) |start T_No_Confirm |Confirm
| |IF(NSLPdata) |
| | tg_RecvMsg(NSLPdata)|
| | to Appl.|
| | |
5) |rx_Confirm |Install Upstream MRS |Established
| | |Upstream
| | |MRS
| | |
6) |rx_Data |tx_Response(No_MRS_ |Wait
| | installed)|Confirm
| | |
Tsenov, et al. Informational [Page 24]RFC 5972 GIST State Machine October 2010
14)|(Tg_ERROR)|| |(Delete MRS) |IDLE
|(Tg_MA_Error) |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
-----------
State: Established Upstream MRS
-----------
+Transition
| |Condition |Action |State
v--+------------------------+-------------------------+-----------
7) |(rx_Query)&& |Delete MRS |Wait
|(ConfirmRequired) |tx_Response |Confirm
| |start T_No_Confirm |
| |IF(MA is used) |
| | (Delete MA)|| |
| | (Stop using shared MA)|
| |IF(NSLPdata) |
| | tg_RecvMsg(NSLPdata) |
| | to Appl.|
| | |
8) |(timeout T_Expire_RNode)|Delete MRS |IDLE
||| |tg_NetworkNotification |
|(tg_SetStateLifetime(0))|IF(MA is used) |
| | (Delete MA)|| |
| | (Stop using shared MA)|
| | |
9) |tg_SendMsg |IF(!UpstreamPeerInfo) |Established
| | Queue NSLP data |Upstream
| |ELSE tx_Data |MRS
| | |
10)|rx_Query |IF (NewPeer) |Established
| | Update UpstreamPeerInfo|Upstream
| |tx_Response |MRS
| |restart T_Expire_RNode |
| | |
11)|rx_Query(MAinfo)&& |Delete UpstreamPeerInfo |Established
|(!ConfirmRequired) |restart T_Expire_RNode |Upstream
| |tx_Response(MAinfo) |MRS
| | |
Tsenov, et al. Informational [Page 25]RFC 5972 GIST State Machine October 2010
12)|rx_Data |IF(UpstreamPeerInfo) |Established
| | (tg_RecvMsg to Appl.)|Upstream
| | &&(restart_T_Expire_ |MRS
| | RNode)|
| |ELSE |
| | tx_Error(No_MRS_ |
| | installed)|
| | |
13)|rx_Confirm |Install UpstreamPeerInfo |Established
| |tx_Data(queued_NSLP_data)|Upstream
| | |MRS
| | |
14)|(Tg_ERROR)|| |(Delete MRS) |IDLE
|(Tg_MA_Error) |IF (MA is used) |
| | ((Delete MA)|| |
| | (Stop using shared MA))|
| |Tg_NetworkNotification |
| | |
---+------------------------+-------------------------+-----------
Tsenov, et al. Informational [Page 26]RFC 5972 GIST State Machine October 2010
Authors' Addresses
Tseno Tsenov
Sofia, Bulgaria
EMail: tseno.tsenov@mytum.de
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
EMail: Hannes.Tschofenig@nsn.com
Xiaoming Fu (editor)
University of Goettingen
Computer Networks Group
Goldschmidtstr. 7
Goettingen 37077
Germany
EMail: fu@cs.uni-goettingen.de
Cedric Aoun
Consultant
Paris, France
EMail: cedaoun@yahoo.fr
Elwyn B. Davies
Folly Consulting
Soham, Cambs, UK
Phone: +44 7889 488 335
EMail: elwynd@dial.pipex.com
Tsenov, et al. Informational [Page 27]
