📄 rfc3215.txt
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-- Downstream Lost
The LSR loses its LDP session with a downstream LDP peer.
-- Internal SetUp
For some reason, e.g. a configuration request of a traffic
engineering tunnel, or recognizing a new FEC could trigger an
Internal SetUp event to set up a new LSP from this node.
-- Internal Destroy
The LSR send an Internal Destroy event to tear down an LSP.
-- Internal Cross-Connect
The LSR send an Internal Cross-Connect to splice two LSPs into one
LSP. This happens when a LSR switches over to a better next hop.
Boscher, et al. Informational [Page 8]
RFC 3215 LDP State Machine January 2002
-- Internal New NH
The LSR decides to switch over the better next hop.
2.2.4 State Transitions
The following diagram describes briefly the state transitions.
+-------------------+
| |<-------------------+
+-------->| IDLE | |
| | |----------+ |
| +-------------------+ | |
|(LDP Release) | | |
|(LDP Upstream |(LDP Request 1) | | (LDP Release)
| Abort |(Internal SetUp) | | (Upstream Lost)
|(Internal Destroy) | | |
|(Upstream Lost) v | |
| +-------------------+ | |
+---------| | | |
| RESPONSE_AWAITED | | |
+---------| | | |
| +-------------------+ | |
| | | |
|(Downstream Lost) |(LDP Mapping) | |
|(LDP Downstream | | |
| NAK) | +---------------+ |
| | | (LDP Request 2) |
| | | |
| v v |
| +-------------------+ (LDP Withdraw 1) |
| | | (Internal Destroy) |
| | ESTABLISHED |------------>-------+
| | | |
| +-------------------+ |
| | |
| | |
| |(LDP Withdraw 2) | (LDP Upstream
| |(Downstream Lost) | Abort)
| | |
| v |
| +-------------------+ |
| | | |
+-------->| RELEASE_AWAITED |------------>-------+
| |
+-------------------+
Boscher, et al. Informational [Page 9]
RFC 3215 LDP State Machine January 2002
2.2.5 State Machine
2.2.5.1 State -- "IDLE"
State: IDLE
Event: LDP Request
New State: Depends upon the action routine.
Actions:
If this LSR is the LSP Egress or Proxy Egress [2]
Then:
Choose an upstream label, connect this upstream label to the local
IP forwarding module, allocate the resources, send the LDP-MAPPING
upstream with the upstream label, and go to the new state
`ESTABLISHED'.
else
Obtain a next hop (or interface) with the FEC specified in the
LDP-REQUEST, propagate the LDP-REQUEST, with newly assigned
Message ID by this LSR, towards the obtained next hop, and go to
the new state `RESPONSE_AWAITED'.
If the LSR uses the independent control mode [2], choose an
upstream label, connect this upstream label to the local IP
forwarding module, go to the ESTABLISHED state and send an LDP-
MAPPING upstream with the upstream label.
If unable to process the request for any reason, issue an LDP-NAK to
the sender with the appropriate error code, go to IDLE and delete the
LSP Control Block.
State: IDLE
Event: LDP Mapping
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: LDP Release
Boscher, et al. Informational [Page 10]
RFC 3215 LDP State Machine January 2002
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: LDP Withdraw
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: LDP Upstream Abort
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: LDP Downstream NAK
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: Upstream Lost
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Boscher, et al. Informational [Page 11]
RFC 3215 LDP State Machine January 2002
Event: Downstream Lost
New State: IDLE
Actions:
Ignore the event. It is an internal implementation error.
State: IDLE
Event: Internal SetUp
New State: RESPONSE_AWAITED
Actions:
Set up the Trigger Control Block pointer,
Obtain a next hop (or interface) with the FEC specified in the
Internal SetUp message, send a LDP-REQUEST towards the obtained
next hop, and go to the new state `RESPONSE_AWAITED'.
State: IDLE
Event: Internal Destroy
New State: IDLE
Actions:
Ignore. It is an internal implementation error.
State: IDLE
Event: Internal Cross-Connect
New State: IDLE
Actions:
Ignore. It is an internal implementation error.
State: IDLE
Event: Internal New NH
New State: IDLE
Boscher, et al. Informational [Page 12]
RFC 3215 LDP State Machine January 2002
Actions:
Ignore. It is an internal implementation error.
2.2.5.2 State -- "RESPONSE_AWAITED"
State: RESPONSE_AWAITED
Event: LDP Request
New State: RESPONSE_AWAITED
Actions:
Ignore the event. It is an internal implementation error. A non
VC merge ATM LSR must create a new LSP control block for a new LDP
request.
State: RESPONSE_AWAITED
Event: LDP Mapping
New State: ESTABLISHED
Actions:
1) If the LSP is triggered by the local router (Trigger Control
Block Pointer is not zero), send event `Internal LSP UP' to the
Trigger control block.
2) Else If the LSR uses the ordered control mode, choose an
upstream label.
3) Connect the upstream label to the downstream label. Allocate
the resources. Propagate the LDP-MAPPING upstream with the
upstream label.
If unable to process the message, disconnect the upstream label
from the downstream label, free the upstream label, release the
resources, send an LDP-RELEASE downstream and an LDP-NAK upstream
with status (No Label Resources [4]), go to IDLE and delete the
LSP Control Block.
State: RESPONSE_AWAITED
Event: LDP Release
New State: IDLE
Boscher, et al. Informational [Page 13]
RFC 3215 LDP State Machine January 2002
Actions:
If the LSR uses the independent control mode, free the upstream
label.
Send an LDP-ABORT downstream, go to IDLE and delete the LSP
Control Block.
Note: This should only occur if the LSR uses the independent
control mode. In the ordered control mode, no upstream label
mapping will have been sent corresponding to this LSP while
waiting for a label mapping from downstream.
State: RESPONSE_AWAITED
Event: LDP Withdraw
New State: RESPONSE_AWAITED
Actions:
Ignore the event. It's a protocol error from the downstream LSR.
State: RESPONSE_AWAITED
Event: LDP Upstream Abort
New State: IDLE
Actions:
If the LSR uses the independent control mode, free the upstream
label.
Send an LDP-ABORT downstream.
Delete the LSP Control Block.
State: RESPONSE_AWAITED
Event: LDP Downstream NAK
New State: Depends on the action routine.
Boscher, et al. Informational [Page 14]
RFC 3215 LDP State Machine January 2002
Actions:
1. If the LSP is triggered by the local router (Trigger Control
Block Pointer is not zero), send event `Internal LSP DOWN' to
the Trigger control block, go to IDLE and delete the LSP
Control Block.
2. Else If the LSR uses the independent control mode, send an LDP-
WITHDRAW upstream and go to state `RELEASE_AWAITED'.
If the LSR uses the ordered control mode, send an LDP-NAK
upstream, go to IDLE and delete the LSP Control Block.
State: RESPONSE_AWAITED
Event: Upstream Lost
New State: IDLE
Actions:
If the LSR uses the independent control mode, free the upstream
label.
Send an LDP-ABORT downstream, go to IDLE and delete the LSP
Control Block.
State: RESPONSE_AWAITED
Event: Downstream Lost
New State: Depends on the action routine.
Actions:
1. If the LSP is triggered by the local router (Trigger Control
Block Pointer is not zero), send event `Internal LSP DOWN' to
the trigger control block, go to IDLE and delete the LSP
Control Block.
2. Else, If the LSR uses the independent control mode, free the
upstream label and send an LDP-WITHDRAW upstream and go to
state `RELEASE_AWAITED'.
If the LSR uses the ordered control mode, send an LDP-NAK upstream
(with a status `No Route' [4]), go to IDLE and delete the LSP
Control Block.
Boscher, et al. Informational [Page 15]
RFC 3215 LDP State Machine January 2002
State: RESPONSE_AWAITED
Event: Internal SetUp
New State: RESPONSE_AWAITED
Actions:
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