NSIS X. Fu
B. Schloer
Internet-Draft Univ. Goettingen
Expiration Date: June 24, 2007 H. Tschofenig
T. Tsenov
Siemens
December 25, 2006
QoS NSLP State Machine
draft-fu-nsis-qos-nslp-statemachine-05.txt
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Copyright Notice
Copyright (C) The Internet Society (2006). All Rights Reserved.
Abstract
This document describes a state machine for the NSIS Signaling Layer
Protocol for Quality-of-Service signaling (QoS NSLP). A combined
state machine for QoS NSLP entities at different locations of a flow
path is presented in order to illustrate how QoS NSLP may be
implemented.
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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 . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 Common Procedures . . . . . . . . . . . . . . . . . . . . 7
5.2 Common Variables . . . . . . . . . . . . . . . . . . . . . 7
5.3 Events . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Assumptions . . . . . . . . . . . . . . . . . . . . . . . 9
6. Basic State Machine Concept . . . . . . . . . . . . . . . . 11
6.1 The QoS NSLP Daemon . . . . . . . . . . . . . . . . . . . 11
6.2 States, Events and Callback Functions . . . . . . . . . . 12
6.3 Timer . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.4 The Toggle Flag . . . . . . . . . . . . . . . . . . . . . 13
7. State Machine for QoS NSLP nodes . . . . . . . . . . . . . . 13
7.1 State ST_IDLE . . . . . . . . . . . . . . . . . . . . . . 14
7.2 State ST_WR . . . . . . . . . . . . . . . . . . . . . . 16
7.3 State ST_INST . . . . . . . . . . . . . . . . . . . . . . 18
8 Actions and Transitions . . . . . . . . . . . . . . . . . . . 21
8.1 State ST_IDLE . . . . . . . . . . . . . . . . . . . . . . 21
8.2 State ST_WR . . . . . . . . . . . . . . . . . . . . . . 22
8.3 State ST_INST . . . . . . . . . . . . . . . . . . . . . . 23
9. Security Considerations . . . . . . . . . . . . . . . . . . 25
10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 25
11. Change History . . . . . . . . . . . . . . . . . . . . . . 26
11.1 Changes in Version -01 . . . . . . . . . . . . . . . . 26
11.2 Changes in Version -02 . . . . . . . . . . . . . . . . 26
11.3 Changes in Version -03 . . . . . . . . . . . . . . . . 26
11.3 Changes in Version -04 . . . . . . . . . . . . . . . . 26
11.4 Changes in Version -05 . . . . . . . . . . . . . . . . 26
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 27
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
13.1 Normative References . . . . . . . . . . . . . . . . . . 28
13.2 Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. ASCII versions of the state diagrams . . . . . . . . 29
A.1 State ST_IDLE . . . . . . . . . . . . . . . . . . . . . 29
A.2 State ST_WR . . . . . . . . . . . . . . . . . . . . . 32
A.3 State ST_INST . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 40
Intellectual Property and Copyright Statements . . . . . . . 41
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1. Introduction
This document describes a state machine for QoS NSLP [1], trying to
show how QoS NSLP can be implemented to support its deployment. The
state machine described in this document is illustrative of how the
QoS NSLP protocol defined in [1] may be implemented for QoS NSLP
nodes in the flow path. Where there are differences [1] are
authoritative. The state machine diagrams are informative only.
Implementations may achieve the same results using different methods.
According to [1], there are several possibilities for QoS NSLP
signaling, at least including the following: - end-to-end signaling
vs. scoped signaling - sender-initiated signaling vs. receiver-
initiated signaling.
The messages used in the QoS NSLP protocol can be summarized as
follows:
Requesting message Responding message
------------------------+---------------------------
RESERVE |None or RESERVE or RESPONSE
QUERY |RESERVE or RESPONSE
RESPONSE |NONE
NOTIFY |NONE
------------------------+---------------------------
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].
The complete text is reproduced here:
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,
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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 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 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 of 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, i.e., 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 of 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
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variables are initialized to FALSE before the state machine execution
begins. Second, the following notational shorthand is specific to
this document:
<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 }
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Compound statement. Braces are used to group statements that are
executed together as if they were a single statement.
!=
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.
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5. Common Rules
Throughout the document we use terms defined in the [1], such as flow
sender, flow receiver, QUERY, RESERVE or RESPONSE.
5.1 Common Procedures
tx_reserve():
Transmit RESERVE message
tx_response():
Transmit RESPONSE message
tx_query():
Transmit QUERY message
tx_notify():
Transmit NOTIFY message
install_qos_state():
Install the local QoS state.
delete_qos_state():
Delete the local QoS state.
send_info_to_app():
Report information to the application.
RMF():
Performs Resource Management Function and returns the following
values{AVAIL, NO_AVAIL}.
is_local(RII):
Checks the RII object of received RESPONSE message if it is
requested by current node or other upstream node. Returns values
{true, false}.
is_local(RSN):
Checks The RSN object of the received RESPONSE message if it is
requested by current node. Returns values {true, false}.
process_query():
Processes a Query message and provides the requested info
5.2 Common Variables
RII:
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Request Identification Information (RII) object.
RSN:
Reservation Sequence Number (RSN) object.
INFO:
Info_Spec object. Takes values:
- 0x02 - Success values
- 0x04 - Transient Failure values
QSPEC:
QoS specification object.
T-Flag:
Tear flag. Indicates to tear down reservation state. Takes values
{true, false}.
Q-Flag:
Request Reduced Refreshes flag of common message header. Takes
values {true, false}.
R-Flag:
Reserve-Init flag (QUERY) or Replace flag (RESERVE). Indicates a
Receiver Initiated Reservation request in a QUERY message or an
replacing RESERVE in a RESERVE message. Takes values {true,
false}.
S-Flag:
Scoping flag of common message header. Takes values
{true="Next_hop", false="Whole_path"}.
setRII:
If set a RII object will be included into the message. Takes
values {true, false}.
ReducedRefresh:
Keeps information if Reduced refresh method may be used for
refreshing a installed QoS state. Takes value {"On","Off"}.
FlowID:
Flow ID kept by the installed QoS state.
Nodepos:
Position of the QoS NSLP node. Takes values {"QNI", "QNE", "QNR"}.
Toggle:
Flag to indicate whether the direction of a new message has to be
changed compared to the direction of a received one. Takes values
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{true, false}.
Direction:
Direction, in which the message has to be sent. Takes values
{DOWNSTREAM, UPSTREAM}.
SII:
Source Identification Information entry. Takes values:
- CurrSII - SII entry stored for current installed QoS state.
(Assumed to be the one for the direction where the message comes
from e.g.Upstream/Downstream)
- newSII - SII of the received message is different from the SII
stored for the current installed QoS state.
5.3 Events
EV_TG_QUERY:
External trigger to send a QUERY message.
EV_RX_QUERY:
QUERY message received
EV_RX_NOTIFY:
NOTIFY message received
EV_TG_RESERVE:
External trigger to send a RESERVE message.
EV_RX_RESERVE:
RESERVE message received
EV_RX_RESPONSE:
RESPONSE message received
EV_TIMEOUT_RESPONSE:
Wait-Response interval timer expiration
EV_TIMEOUT_REFRESH:
Refresh interval timer expiration
EV_TIMEOUT_STATE_LIFETIME:
State lifetime timer expiration
5.4 Assumptions
- For simplification not all included objects in a message are shown.
Only those that are significant for the case are shown. The State
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Machine does not present handling of messages that are not
significant for management of the states such as certain NOTIFY
and QUERY messages.
- The State Machine represents handling of messages of the same
Session ID and with no protocol errors. Separate parallel
instances of the state machines should handle messages for
different Session IDs.
- Default message handling should be defined for messages with
different Session IDs that have impact on current session state
and error messages. This is not included in the current version.
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6 Basic State Machine Concept
6.1 The QoS NSLP Daemon
The QoS NSLP Daemon (qosd) listens for incoming messages from the
local application and for messages coming over the network from GIST.
For each new SessionID (SID) a new State Machine (FSM) is created as
shown in the diagram below.
Incoming messages from the client application are checked for the
type of the message (QUERY or RESERVE) and for the SID. A table is
searched for the given SID. If it is not found, a new FSM is created
and its address together with the SID is added to the table. If the
type of the message is a QUERY with set R-Bit, a Receiver Initiated
Reservation is requested and the node position is QNR, in all other
cases the node position is QNI. If the SID is found, the address of
the FSM is returned. Now the FSM is triggered with the corresponding
event of the message (EV_TG_QUERY, EV_TG_RESERVE). If the FSM returns
to the qosd in ST_IDLE, it is deleted together with its table entry.
For a message arriving from GIST, the procedure is almost the same.
The table is searched for the given SID. If it is not found, then the
IP-address of the MRI is compared to the local IP-address. If the
arriving message is requesting a Receiver Initiated Reservation and
the destination address is equal to the local address then the node
position is QNR. If the addresses are equal and no Receiver Initiated
Reservation is requested then the node position is QNI. If the
addresses are not the same, a new FSM for a QNE is created. Also
here, the corresponding FSM is triggered with the event according to
the arrived message and deleted when returning in ST_IDLE.
+-------+ +-------+ +-------+
| | | | | |
| FSM 1 | | FSM 2 | | FSM n |
| | | | | |
+-------+ +-------+ +-------+
\ | /
\ | /
\ | /
\ | /
\ | /
+-------+
| |
| qosd |
| |
+-------+
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Figure 1
6.2 States, Events and Callback Functions
Three States are defined: ST_IDLE, ST_WR and ST_INST. A new created
FSM is starting automatically in ST_IDLE. In this state no
reservation state is installed no responses to previously sent
messages are expected. In ST_WR the FSM is waiting for a response to
a previously sent message, but no reservation state is installed. In
ST_INST reservation state has been installed and incoming messages
are processed.
The following table provides to a given state and a triggered event
the function which has to be executed by the FSM. Example: when
EV_RX_QUERY is triggered in state ST_IDLE, the function
idle__rx_query is executed.
+-----------+----------------------------+-------------------------------+
| State | Event | Executed Function |
+-----------+----------------------------+-------------------------------+
| ST_IDLE | EV_TG_QUERY | idle__tg_query |
| ST_IDLE | EV_RX_QUERY | idle__rx_query |
| ST_IDLE | EV_TG_RESERVE | idle__tg_reserve |
| ST_IDLE | EV_RX_RESERVE | idle__rx_reserve |
| ST_IDLE | EV_RX_RESPONSE | idle__rx_response |
+-----------+----------------------------+-------------------------------+
| ST_WR | EV_TG_QUERY | wr__tg_query |
| ST_WR | EV_RX_QUERY | wr__rx_query |
| ST_WR | EV_TG_RESERVE | wr__tg_reserve |
| ST_WR | EV_RX_RESERVE | wr__rx_reserve |
| ST_WR | EV_RX_RESPONSE | wr__rx_response |
| ST_WR | EV_TIMEOUT_WAITRESP | wr__timeout_waitresp |
+-----------+----------------------------+-------------------------------+
| ST_INST | EV_TG_QUERY | inst__tg_query |
| ST_INST | EV_RX_QUERY | inst__rx_query |
| ST_INST | EV_RX_NOTIFY | inst__rx_notify |
| ST_INST | EV_TG_RESERVE | inst__tg_reserve |
| ST_INST | EV_RX_RESERVE | inst__rx_reserve |
| ST_INST | EV_RX_RESPONSE | inst__rx_response |
| ST_INST | EV_TIMEOUT_WAITRESP | inst__timeout_waitresp |
| ST_INST | EV_TIMEOUT_REFRESH | inst__timeout_refresh |
| ST_INST | EV_TIMEOUT_STATELIFETIME | inst__timeout_statelifetime |
+-----------+----------------------------+-------------------------------+
Figure 2
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6.3 Timer
The Response Timer at QNI and QNE is started when a RESPONSE message
is expected to a sent QUERY or RESERVE. When a reservation is set up,
the Refresh Timer are started at QNI and QNE and the StateLife Timer
are started at QNE and QNR. When the Refresh Timer times out, a
refreshing RESERVE is sent peer to peer towards the QNR and the
Response Timer are started because a confirmation is expected. On
arrival the StateLife Timer is restarted.
If the confirmation is not sent back, then the refreshing RESERVEs
are resent up to MAX_RETRY. After MAX_RETRY has been reached,
reservation state is removed and a RESERVE with set T-Flag is sent to
the QNR to remove reservation state along the path. When no
refreshing RESERVE arrive at QNE and QNR, then the StateLife Timer
expires and reservation state is also removed and a RESERVE with set
T-Flag is sent towards the QNR.
+-----------------+-------------------+-------------------+
| QNI | QNE | QNR |
+-----------------+-------------------+-------------------+
| Refresh Timer | Refresh Timer | StateLife Timer |
| Response Timer | Response Timer | |
| | StateLife Timer | |
+-----------------+-------------------+-------------------+
Figure 3
6.4 The Toggle Flag
The Toggle Flag manipulates the direction of the message. When set,
the message is sent in the opposite direction compared to the
received one. The boolean operation XOR is used. Example, where true
is the toggle flag: DOWNSTREAM XOR true = UPSTREAM (0 XOR 1 = 1).
7. State machine
The following section presents the state machine diagrams of QoS NSLP
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7.1 State ST_IDLE
(see the .pdf version for missing diagram or
refer to Appendix A.1 if reading the .txt version)
Figure 4
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(see the .pdf version for missing diagram or
refer to Appendix A.1 if reading the .txt version)
Figure 5
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7.2 State ST_WR
(see the .pdf version for missing diagram or
refer to Appendix A.2 if reading the .txt version)
Figure 6
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(see the .pdf version for missing diagram or
refer to Appendix A.2 if reading the .txt version)
Figure 7
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7.3 State ST_INST
(see the .pdf version for missing diagram or
refer to Appendix A.3 if reading the .txt version)
Figure 8
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(see the .pdf version for missing diagram or
refer to Appendix A.3 if reading the .txt version)
Figure 9
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(see the .pdf version for missing diagram or
refer to Appendix A.3 if reading the .txt version)
Figure 10
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8. Actions and Transitions
This chapter describes the operation of the FSM.
8.1 State ST_IDLE
8.1.1 idle__tg_query
The local application has triggered a QUERY in ST_IDLE. If the node
position is QNR and a Receiver Initiated Reservation is requested,
then a QUERY message is constructed with set R-Flag together with a
PC and a QSPEC. No RII object is included because a RESPONSE message
does not need to be triggered. In case of a normal QUERY a RII object
is included to match back the response. It also contains a QSPEC to
perform a query along the path. In both cases the variable Direction
is set to DOWNSTREAM and the Response Timer is started. The message
is sent downstream and transition is made to ST_WR.
8.1.2 idle__rx_query
This function is executed when a QUERY message has arrived over the
network from GIST and the FSM is in State ST_IDLE. If a QSPEC object
is present, then it is passed to the RMF. If the R-Flag is not set
and the node position is QNE and the Scoping Flag is not set, then a
new QUERY message with the returned QSPEC from the RMF is constructed
and sent further along the path. If the Scoping Flag is set or the
node position is QNI or QNR, then a RESPONSE message with the
received RII object, an INFO object with Error Class SUCCESS and the
QSPEC object is sent back with set Toggle Flag. Transition is made to
ST_IDLE.
If the R-Flag is set and the node position is QNI and the RMF returns
that no resources are available, then a RESPONSE with a RSN object
and a INFO object with Error Class Failure is sent back. Transition
is done to ST_IDLE.
In the other case where resources are available, the RMF performs
resource reservation. A new RESERVE message is created, the Q-Flag is
set, if Reduced Refreshes were requested, a RSN object, a PC and the
returned QSPEC is added. If a response is requested, then a RII
object is added additionally and the response timer is started.
Direction is set to UPSTREAM and the message is sent upstream. The
refresh timer is started. Transition is made to ST_INST.
8.1.3 idle__tg_reserve
The local application has triggered a RESERVE message to be sent. If
the T-Flag is set, then a RESERVE message is sent downstream with set
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T-Flag and with a RSN object. Transition is made to ST_IDLE.
If the node position is QNI and the RMF returns that no resources are
available, then a FAILURE is sent back to the local application.
Transition is made to ST_IDLE.
If resources are available, then the RMF performs resource
reservation, a new RESERVE message is created, the Q-Flag is set if
reduced refreshes are requested, a RSN object, a PC and the returned
QSPEC is added. If a response is requested, then a RII object is
added additionally and the response timer is started. Direction is
set to DOWNSTREAM and the message is sent downstream. The refresh
timer is started. Transition is made to ST_INST.
8.1.4 idle__rx_reserve
A RESERVE from the network in ST_IDLE has arrived. If the T-Flag is
set, if the node position is QNE and if the Scoping Flag is not set,
then the message is forwarded further along the path with
toggle=false. Transition is made to ST_IDLE.
If the T-Flag is not set and the RMF returns that no resources are
available, then a RESPONSE with a RII (if available, else with RSN
object) and a INFO object with Error Class Failure is sent back.
Transition is done to ST_IDLE.
If resources are available, then the RMF performs resource
reservation, the State Timer is started. If the node position is QNE
and the Scoping Flag is not set, then a new RESERVE message is
created out of the old one and sent further downstream. The Response
Timer is started additionally to the Refresh Timer. If the Q-Flag
was set in the received message, the variable ReducedRefreshes is set
to true and a NOTIFY with the corresponding INFO object is sent back
with toggle=true. If the received message contained a RII object and
the node is QNR or QNE and the Scoping Flag is set, then a RESPONSE
with this RII object and INFO=SUCCESS is sent back. Transition is
made to ST_INST.
8.1.5 idle__rx_response
If the node position is QNE and the Scoping Flag is not set, then the
RESPONSE message is forwarded further along the path. Transition is
made to ST_IDLE.
8.2 State ST_WR
8.2.1 wr__tg_query
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The local application has triggered a QUERY in ST_WR. The value of
the RII object is stored and the message is sent to the stored
direction together with a QSPEC object. The Response Timer is
started. Transition is made to ST_WR.
8.2.2 wr__rx_query
This function is executed when a QUERY message has arrived over the
network from GIST and the FSM is in State ST_WR. If a QSPEC object is
present, then it is passed to the RMF. If the R-Flag is not set and
the node position is QNE and the Scoping Flag is not set, then a new
QUERY message with the returned QSPEC from the RMF is constructed and
sent further along the path. If the Scoping Flag is set or the node
position is QNI or QNR, then a RESPONSE message with the received RII
object, an INFO object with Error Class Success and the QSPEC object
is sent back with set Toggle Flag. Transition is made to ST_WR.
8.2.3 wr__tg_reserve
See idle__tg_reserve.
8.2.4 wr__rx_reserve
See idle__rx_reserve. If the node position is QNR and the stored
Direction is DOWNSTREAM, then this is the requested RESERVE message
for the Receiver Initiated Reservation. The Response Timer is
stopped. Transition is made to ST_INST.
8.2.5 wr__rx_response
In ST_WR a RESPONSE message has arrived. If the node position is QNE
and no Scoping Flag is set, then the RESPONSE message is forwarded.
If the RII object is stored to match back a response, then the
Response Timer is stopped. If no more Response Timer are pending,
transition is made to ST_IDLE, otherwise to ST_WR.
8.2.6 wr__timeout_response
A Response Timer has timed out while in ST_WR. If the maximum number
of retries has been reached, then the Response Timer is stopped. If
no more Response Timer are pending, transition is done to ST_IDLE,
otherwise to ST_WR. If the maximum number of retransmissions has not
been reached, then the stored message is resent and transition is
made to ST_WR.
8.3 State ST_INST
8.3.1 inst__tg_query
Fu, et al. [Page 23]
Internet-Draft QoS NSLP State Machine December 2006
See wr__tg_query. Transition is made to ST_INST.
8.3.2 inst__rx_query
See wr__rx_query. Transition is made to ST_INST.
8.3.3 inst__rx_notify
If Reduced Refreshes were requested, then the Error Code is checked
whether the next peer has accepted them. After receiving the RII
object Reduced Refreshes can be used as refreshing RESERVEs.
Transition is made to ST_INST.
8.3.4 inst__tg_reserve
If the T-Flag is set, then all pending timers are stopped, the
reservation is torn down and the message is sent further along the
path into the stored direction with toggle=false. Transition is done
to ST_IDLE.
8.3.5 inst__rx_reserve
A RESERVE message in ST_INST has arrived. If the T-Flag is set, then
all pending timer are stopped, the reservation is torn down. If the
node position is QNE and the S-Flag is not set, then the RESERVE is
forwarded with toggle=false. Transition is done to ST_IDLE.
If the T-Flag is not set, then this is a refreshing RESERVE. A
RESPONSE with the received RII and INFO=SUCCESS is sent back with
Toggle=false, if the node position is QNR or QNE and the S-Flag is
set. The Statelife Timer is being restarted.
8.3.6 inst__rx_response
In ST_INST a RESPONSE message has arrived. If the node position is
QNE and no Scoping Flag is set, then the RESPONSE message is
forwarded. If the RII object is stored to match back a response, then
the Response Timer is stopped. If the received Error Code of the INFO
object is SUCCESS, then the Response Timer is started. Transition is
done to ST_INST.
If the Error Code is FAILURE, then the reservation state is deleted
and pending timer are stopped. Transition is made to ST_IDLE.
8.3.7 inst__timeout_response
A Response Timer has timed out while in ST_INST. If the maximum
number of retries has been reached, then all pending timer are
Fu, et al. [Page 24]
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stopped. Transition is made to ST_IDLE. If maximum numbers of
retransmissions has not been reached, then the refreshing RESERVE is
resent and the Response Timer is restarted. Transition is made to
ST_INST.
8.3.8 inst__timeout_refresh
A RESERVE message is created. If Reduced Refreshes are accepted, no
QSPEC object is added. If the refresh is sent along the whole path,
then a RII object is added. The Response and the Refresh Timer is
restarted. Transition is made to ST_INST.
8.3.9 inst__timeout_statelifetime
The Statelife Timer timed out in ST_INST. All active timer are
stopped and existing reservations are removed. If the node position
is not QNR, then a RESERVE message with T-Flag set is created and
sent into the stored direction. Transition is done to ST_IDLE.
9. Security Considerations
This document does not raise new security considerations. Any
security concerns with QoS NSLP are likely reflected in security
related NSIS work already (such as [1] or [6]).
For the time being, the state machine described in this document does
not consider the security aspect of QoS NSLP protocol itself. A
future version of this document will add security relevant states and
state transitions.
10. Open Issues
This document tries to describe possible states and transitions for
QoS NSLP according to its current specification [1], Section 5. We
found some issues during the development of the state machines.
1. Bi-directional reservation is difficult to support as the state
machine becomes quite complex (note at one particular point in
time the protocol state engine can be only in one state).
2. How to signal unsuccessful reservation for Receiver initiated
reservation (No RII included; a resulting Response(RSN) cannot be
forwarded further than the next peer). We use NOTIFY message.
3. The case of unsuccessful reservation at a QNE node and no RII
specified by upstream nodes. According to the spec RESPONSE(RSN)
should not be forwarded further than the next peer. Currently we
use NOTIFY(RSN) that is sent further to the upstream nodes.
Fu, et al. [Page 25]
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4. We assume that handling of QoS state lifetime expiration event is
based on the local policy of the node. NOTIFY/Reserve(Ton)
messages might be sent to other peers.
5. The draft states that RESERVE message MUST be sent only towards
the QNR. This is not the case when re-routing procedure is done
and RESERVE(Ton) message should be sent from merging QNE node for
deleting the old branch. We believe this is towards the QNI.
6. Re-routing functionality described in this document is not
complete and need further consideration.
11. Change History
11.1 Changes in Version -01
1. Notation of the nodes changed to QNI, QNE and QNR.
2. Description of soft state refresh functionality.
3. Support of ACK flag in the common header.
4. Include of QoS NSLP objects, flags from the common header and
entries stored with the installed QoS state in a node: ACK,
Replace, RSN, Error_SPEC, QSPEQ, FlowID, SII.
5. Initial description of Re-routing functionality.
6. For support of all listed changes, some notations are changed.
11.2 Changes in Version -02
1. Switch to .pdf format of the draft and include graphic diagrams.
2. Update notation from "Summary refresh" to "Reduced refresh"
3. Description of QoS reservation update/upgrade
11.3 Changes in Version -03
1. Deep review of the state machine architecture
11.4 Changes in Version -04
1. Reduced the three state machines of QNI, QNE and QNR to one for
all nodes.
2. Introduced new flags to have a finer control of the direction of
the message to be sent.
11.5 Changes in Version -05
1. Combined ST_WR2 and ST_INST into ST_INST
2. Support for Q-Flag in common header
3. Explanations on the execution of the State Machine added
Fu, et al. [Page 26]
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12. Acknowledgments
The authors would like to thank Sven Van den Bosch and Christian
Dickmann for their feedback.
Fu, et al. [Page 27]
Internet-Draft QoS NSLP State Machine December 2006
13. References
13.1. Normative References
[1] Manner, J., Karagiannis, G. and McDonald, A., "NSLP for
Quality-of-Service Signaling", Internet draft, draft-
ietf-nsis-qos-nslp-11 (work in progress), June 2006.
[2] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
13.2. Informative References
[3] Vollbrecht, J., Eronen, P., Petroni, N., and Y. Ohba,
"State Machines for Extensible Authentication Protocol
(EAP) Peer and Authenticator", draft-ietf-eap-
statemachine-06 (work in progress), December 2004.
[4] Institute of Electrical and Electronics Engineers, "DRAFT
Standard for Local and Metropolitan Area Networks: Port-
Based
Network Access Control (Revision)", IEEE 802-1X-REV/D11,
July 2004.
[5] Ohba, Y., "State Machines for Protocol for Carrying
Authentication for Network Access (PANA)",
draft-ohba-pana-statemachine-01 (work in progress),
February 2005.
[6] Tschofenig, H. and D. Kroeselberg, "Security Threats for
NSIS", draft-ietf-nsis-threats-06 (work in progress),
October 2004.
Fu, et al. [Page 28]
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Appendix A. ASCII versions of state diagrams
This appendix contains the state diagrams in ASCII format. Please use
the PDF version whenever possible: it is much easier to understand.
The notation is as follows: 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 ST_IDLE
ST_IDLE::EV_TG_RESERVE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag) { | ST_IDLE |
| tx_reserve(T-Flag, RSN, Direction=DOWNSTREAM); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (Nodepos==QNI) && (RMF()==NO_AVAIL)) { | ST_IDLE |
| send_info_to_app(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (Nodepos==QNI) && (RMF()==AVAIL)) { | ST_INST |
| install_qos_state(); | |
| if(setRII) { | |
| tx_reserve(Q-Flag, RSN, RII, PC, QSPEC, | |
| Direction=DOWNSTREAM); | |
| } else { | |
| tx_reserve(Q-Flag, RSN, PC, QSPEC, | |
| Direction=DOWNSTREAM); | |
| } | |
| startRefreshTimer(); | |
| startResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 11
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ST_IDLE::EV_RX_RESERVE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag && (Nodepos==QNE) && (!S-Flag)) { | ST_IDLE |
| tx_reserve(T-Flag, RSN, Toggle=false); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (RMF()==NO_AVAIL)) { | ST_IDLE |
| tx_response(RII/RSN, INFO(FAILURE), Toggle=true) | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (RMF()==AVAIL)) { | ST_INST |
| install_qos_state(); | |
| startStateTimer(); | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| Direction=DOWNSTREAM; | |
| tx_reserve(Toggle=false); | |
| startRefreshTimer(); | |
| startResponseTimer(); | |
| } | |
| if(Q-Flag) { | |
| ReducedRefreshes=true; | |
| tx_notify(INFO(RR_SUPPORTED), Toggle=true); | |
| } | |
| if(RII && ((Nodepos==QNR) || | |
| ((Nodepos==QNE) && S-Flag))) { | |
| Direction=UPSTREAM; | |
| tx_response(RII, INFO(SUCCESS), Toggle=true); | |
| } | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 12
ST_IDLE::EV_TG_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if((Nodepos==QNR) && R-Flag) { | ST_WR |
Fu, et al. [Page 30]
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| tx_query(R-Flag, PC, QSPEC, Direction=DOWNSTREAM); | |
| } else { | |
| tx_query(RII, QSPEC, Direction=DOWNSTREAM); | |
| } | |
| startResponseTimer(); | |
| | |
+---------------------------------------------------------+-----------+
Figure 13
ST_IDLE::EV_RX_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| queryRMF(QSPEC); | ST_IDLE |
| if(!(R-Flag && (Nodepos==QNI))) { | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_query(QSPEC, Toggle=false); | |
| } else { | |
| tx_response(RII/RSN, INFO(SUCCESS), | |
| QSPEC, Toggle=true); | |
| } | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(R-Flag && (Nodepos==QNI) && (RMF()==NO_AVAIL)) { | ST_IDLE |
| tx_response(RSN, INFO(FAILURE), Toggle=true); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(R-Flag && (Nodepos==QNI) && (RMF()==AVAIL)) { | ST_INST |
| install_qos_state(); | |
| if(setRII) { | |
| tx_reserve(Q-Flag, RSN, RII, PC, QSPEC, | |
| Direction=UPSTREAM); | |
| } else { | |
| tx_reserve(Q-Flag, RSN, PC, QSPEC, | |
| Direction=UPSTREAM); | |
| } | |
| startRefreshTimer(); | |
| startResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Fu, et al. [Page 31]
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Figure 14
ST_IDLE::EV_RX_RESPONSE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if((Nodepos==QNE) && (!S-Flag)) { | ST_IDLE |
| tx_response(Toggle=false); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 15
A.2. State ST_WR
ST_WR::EV_RX_RESPONSE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_response(Toggle=false); | |
| } | |
| if(is_local(RII)==true) { | |
| stopResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(TIMER_PENDING==true) | ST_WR |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(TIMER_PENDING==false) | ST_IDLE |
| | |
+---------------------------------------------------------+-----------+
Figure 16
ST_WR::EV_TIMEOUT_RESPONSE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
Fu, et al. [Page 32]
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| | |
| if((MAX_RETRY) && (!TIMER_PENDING)) | ST_IDLE |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((MAX_RETRY) && (TIMER_PENDING)) | ST_WR |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(MAX_RETRY) { | ST_WR |
| tx_query(Direction); | |
| restartResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 17
ST_WR::EV_RX_RESERVE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag && (Nodepos==QNE) && (!S-Flag)) { | ST_IDLE |
| tx_reserve(T-Flag, RSN, Toggle=false); | |
| stopTimers(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (RMF()==NO_AVAIL)) { | ST_IDLE |
| tx_response(RII/RSN, INFO(FAILURE), Toggle=true); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (RMF()==AVAIL)) { | ST_INST |
| install_qos_state(); | |
| startStateTimer(); | |
| if((Nodepos==QNR) && (Direction==DOWNSTREAM)) { | |
| stopResponseTimer(); | |
| } | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_reserve(Toggle=false); | |
| startRefreshTimer(); | |
| startResponseTimer(); | |
| } | |
Fu, et al. [Page 33]
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| if(Q-Flag) { | |
| ReducedRefreshes=true; | |
| tx_notify(info(RR_SUPPORTED), Toggle=true); | |
| } | |
| if(RII && ((Nodepos==QNR) || | |
| ((Nodepos==QNE) && S-Flag))) { | |
| tx_response(RII, INFO(SUCCESS), Toggle=true); | |
| } | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 18
ST_WR::EV_TG_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| tx_query(RII, QSPEC, Direction); | ST_WR |
| startResponseTimer(); | |
| | |
+---------------------------------------------------------+-----------+
Figure 19
ST_WR::EV_RX_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| queryRMF(QSPEC); | ST_WR |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_query(QSPEC, Toggle=false); | |
| } else { | |
| tx_response(RII/RSN, INFO(SUCCESS), QSPEC, | |
| Toggle=true); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 20
ST_WR::EV_TG_RESERVE
Fu, et al. [Page 34]
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+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag) { | ST_IDLE |
| tx_reserve(T-Flag, RSN, Direction=DOWNSTREAM); | |
| stopTimers(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (Nodepos==QNI) && (RMF()==NO_AVAIL)) { | ST_IDLE |
| send_info_to_app(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if((!T-Flag) && (Nodepos==QNI) && (RMF()==AVAIL)) { | ST_INST |
| install_qos_state(); | |
| if(setRII) { | |
| tx_reserve(Q-Flag, RSN, RII, PC, QSPEC, | |
| Direction=DOWNSTREAM); | |
| } else { | |
| tx_reserve(Q-Flag, RSN, PC, QSPEC, | |
| Direction=DOWNSTREAM); | |
| } | |
| startRefreshTimer(); | |
| startResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 21
A.3. State ST_INST
ST_INST::EV_RX_RESPONSE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_response(toggle=false); | |
| } | |
| if(is_local(RII)==true) { | |
| stopResponseTimer(); | |
| } | |
| | |
Fu, et al. [Page 35]
Internet-Draft QoS NSLP State Machine December 2006
+---------------------------------------------------------+-----------+
| | |
| if(INFO==SUCCESS) | ST_INST |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(INFO==FAILURE) { | ST_IDLE |
| delete_qos_state(); | |
| stop_timers(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 22
ST_INST::EV_RX_RESERVE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag) { | ST_IDLE |
| delete_qos_state(); | |
| stopTimers(); | |
| if((Nodepos==QNE) && (!S-Flag)) { | |
| tx_reserve(Toggle=false); | |
| } | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(!T-Flag) { | ST_INST |
| if((Nodepos==QNR) || ((Nodepos==QNE)&&(!S-Flag))) { | |
| if(RII) { | |
| tx_response(RII, RSN, INFO(SUCCESS), | |
| Toggle=true); | |
| } else { | |
| tx_notify(INFO(SUCCESS), Toggle=true); | |
| } | |
| } | |
| restartStateTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 23
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ST_INST::EV_RX_NOTIFY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(ErrorClass==ERRORCLASS_INFO) { | ST_INST |
| if(ErrorCode==RR_NOT_SUPPORTED) { | |
| ReducedRefreshes = false; | |
| } else if(ErrorCode==RR_SUPPORTED) { | |
| ReducedRefreshes = true; | |
| } | |
| } | |
| if(ErrorClass==SUCCESS) { | |
| stopResponseTimer(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 24
ST_INST::EV_TG_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| tx_query(RII, QSPEC, Direction); | ST_INST |
| startResponseTimer(); | |
| | |
+---------------------------------------------------------+-----------+
Figure 25
ST_INST::EV_RX_QUERY
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(!R-Flag) { | ST_INST |
| queryRMF(QSPEC); | |
| if((Nodepos==QNE) && (!S-Flag)) | |
| tx_query(QSPEC, Toggle=false); | |
| } else { | |
| tx_response(RII/RSN, INFO, QSPEC, Toggle=true); | |
| } | |
| } | |
| | |
Fu, et al. [Page 37]
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+---------------------------------------------------------+-----------+
Figure 26
ST_INST::EV_TG_RESERVE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(T-Flag) { | ST_INST |
| delete_qos_state(); | |
| stopTimers(); | |
| tx_reserve(T-Flag, RSN, Direction); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 27
ST_INST::EV_TIMEOUT_RESPONSE
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| if(MAX_RETRY) { | ST_IDLE |
| delete_qos_state(); | |
| stopTimers(); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
| | |
| if(!MAX_RETRY) { | ST_INST |
| tx_reserve(Direction); | |
| restartResponseTimer() | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 28
ST_INST::EV_TIMEOUT_REFRESH
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
Fu, et al. [Page 38]
Internet-Draft QoS NSLP State Machine December 2006
| if(ReducedRefreshes) { | ST_INST |
| if(WholePath) { | |
| tx_reserve(RSN, RII, Direction); | |
| } else { | |
| tx_reserve(RSN, Direction); | |
| } | |
| } else { | |
| if(WholePath) { | |
| tx_reserve(RSN, RII, QSPEC, Direction); | |
| } else { | |
| tx_reserve(RSN, QSPEC, Direction); | |
| } | |
| } | |
| startResponseTimer(); | |
| restartRefreshTimer(); | |
| | |
+---------------------------------------------------------+-----------+
Figure 29
ST_INST::EV_TIMEOUT_STATELIFETIME
+---------------------------------------------------------+-----------+
| Action | new State |
+---------------------------------------------------------+-----------+
| | |
| stopTimers(); | ST_IDLE |
| delete_qos_state(); | |
| if(Nodepos != QNR) { | |
| tx_reserve(T-Flag, RSN, Direction); | |
| } | |
| | |
+---------------------------------------------------------+-----------+
Figure 30
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Authors' Addresses
Xiaoming Fu
University of Goettingen
Telematics Group
Lotzestrasse 16-18
Goettingen 37083
Germany
Email: fu@cs.uni-goettingen.de
Hannes Tschofenig
Siemens
Otto-Hahn-Ring 6
Munich, Bayern 81739
Germany
Email: Hannes.Tschofenig@siemens.com
Tseno Tsenov
Siemens
Otto-Hahn-Ring 6
Munich, Bayern 81739
Germany
Email: tseno.tsenov@mytum.de
Bernd Schloer
University of Goettingen
Telematics Group
Lotzestrasse 16-18
Goettingen 37083
Germany
Email: bschloer@cs.uni-goettingen.de
Fu, et al. [Page 40]
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Fu, et al. [Page 41]