--- 1/draft-ietf-mpls-ldp-state-02.txt 2006-02-05 00:40:47.000000000 +0100 +++ 2/draft-ietf-mpls-ldp-state-03.txt 2006-02-05 00:40:47.000000000 +0100 @@ -1,25 +1,24 @@ - MPLS Working Group Christophe Boscher Internet Draft Pierrick Cheval -Expiration Date: April 2000 Alcatel France +Expiration Date: July 2000 Alcatel Liwen Wu Cisco Eric Gray Lucent - October 1999 + January 2000 LDP State Machine - draft-ietf-mpls-ldp-state-02.txt + draft-ietf-mpls-ldp-state-03.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. @@ -36,118 +35,118 @@ Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved. 1. Abstract In the current LDP specification [4], there is no state machine - specified for processing the LDP messages. We think that defining a + specified for processing LDP messages. We think that defining a common state machine is very important for interoperability between - different ldp implementations. + different LDP and CR-LDP implementations. This document provides state machine tables for ATM switch LSRs. We begin in section 2 by defining a list of terminologies. Then in section 3, we propose two sets of state machine tables for ATM switch LSRs which use downstream-on-demand mode, one method can be used for - non-vc merge-able ATM LSRs, while the other one can be used for the - vc-merge-able ATM LSRs. In section 4, we provides a state machine - for downstream mode ATM LSR. + non-vc merge capable ATM LSRs, while the other one can be used for + the vc-merge capable ATM LSRs. In section 4, we provides a state + machine for downstream unsolicited mode ATM LSRs. - We focus on the LDP state machines and the associated control blocks. - We not describe the "LDP controller" which is in charge of LDP - session initialization, address mapping messages management, routing - interface, etc. Specifically, the LDP specification [4] defines the - state machine for session management. + We focus on the LDP state machines and the associated control blocks + used for establishing and maintaining LSPs. We do not describe state + machines for the "LDP controller" which is in charge of LDP session + initialization, address mapping messages management, routing + interface, etc. which is defined in the LDP specification [4]. Even though the state machines in this document are specific for ATM-LSR, they can be easily adapted for other types of LSRs. -2. Terminologies +2. Terminology - LDP-REQUEST: LDP Label Request message - LDP-MAPPING: LDP Label Mapping message - LDP-WITHDRAW: LDP Label Withdraw message - LDP-RELEASE: LDP Label Release message - LDP-ABORT: LDP Abort message used to abort a LSP setup. - LDP-NAK: LDP Notification message used to reject an LDP message. 3. State Machine for Downstream-on-Demand Mode In this draft, we provide two sets of state machines: one for the ATM - LSR which does not have VC-merge capability, and the other one for - the ATM LSR which does have VC-merge capability. + LSR which does not have VC-merge capability, and the other for the + ATM LSR which does have VC-merge capability. State machine descriptions are given in terms of control blocks, states, events, response actions and state transitions. Control blocks contain the information that is required to support handling of events. A control block may also contain any additional information that is required either of any specific implementation or in support of other required functions. In every case, additional information required to support the procedures defined in the LDP specification [4] or management objects defined in the LDP MIB [3] would be stored in a specific LDP implementation - either as part of the control block structure or in some other way. The state machines cover both independent LSP control and ordered LSP control. - Loop detection and loop prevention message will be processed as + Loop detection and loop prevention messages will be processed as specified in [4]. The impact of loop detection and loop prevention messages on state transitions is left for further study. 3.0 An LSR's Behavior in the Case of a Next Hop Change When there is a topology change and an LSR detects a new better next hop for an LSP, it may behave in 2 different ways: 1) It tries to do a "local repair". This means that it extends the LSP through the new next hop, releases the old path from this LSR forward and then splices into this newly extended LSP. 2) If the LSP is created with the "pinned" option (CR-LDP[5]), the LSR ignores the new next hop change, and the LSP stays unchanged. The - LSR may decide to send an LDP-MAPPING which contains the attribute - about this New Next Hop (NH) change. + LSR may decide to send an LDP-MAPPING containing attributes for this + New Next Hop (NH) that have changed. -3.1. ATM Switch LSR with NO VC-merge +3.1. ATM Switch LSR with No VC-merge Capability In an MPLS domain where some ATM LSRs do not have VC-merge capability, downstream-on-demand mode is required for these ATM LSRs [1]. Also, "conservative label retention mode" is required in this case [1]. - For each LSP, there are 2 kinds of state machines involves: + For each LSP, there are 2 kinds of state machines involved: 1) the LSP Control Block and its state machine which can be used to handle normal LSP setup. It is created when the LSR receives a new LDP Request and it is deleted when the LSP of this request is torn down. 2) the Next Hop Trigger Control Block and its state machine which is used to handle switching over to a better LSP through a different next hop. It is created when the LSR decides to switch over to a better next hop and it is deleted when the LSR finishes switching over to the better next hop. This state machine uses a timer (and has corresponding states) to ensure that switch over occurs in a - timely fashion. + timely fashion after a routing transient has had time to stabilize. 3.1.1 LSP Control Block - For each LSP, an LSP_Control_Block is defined which may contain the + For each LSP, an LSP Control Block is defined which may contain the following information: - Upstream Label Request ID (assigned by the upstream LSR), which is the 'Message Id' in the Label Request Message received from the upstream LSR. - Downstream Label Request ID (assigned by this LSR itself), which is 'Message Id' in the Label Request Message sent to the downstream LSR. @@ -157,66 +156,68 @@ - State - FEC - Upstream Label (assigned by this LSR) - Downstream Label (assigned by the downstream LSR) - Trigger Control Block Pointer, (Only used at the ingress LSR of a - LSP)which points to the control block that triggers setting up this + LSP) that points to the control block that triggers setting up this LSP or tearing down this LSP. - Next Hop Control Block Pointer, which points to the control block which is used for switching over to a better LSP. - The following index combinations can be used to locate a unique - LSP_Control_Block: + The following index combinations can be used to locate a unique LSP + Control Block: - Downstream Label and Downstream LDP Identifier, or - Upstream Label and Upstream LDP Identifier, or - Downstream Label Request ID and Downstream LDP Identifier - Upstream Label Request ID and Upstream LDP Identifier Here is the relationship between different control blocks, the detail - definition of Next Hop Trigger Block is described in section 3.1.6. + definition of Next Hop Trigger Control Block is described in section + 3.1.6. For example, an LSP which transit through (LSR-A, LSR-B, LSR-C, LSR- D): LSR-A ----> LSR-B ---> LSR-C ---> LSR-D The control blocks in LSR-A are: +-----------------------+ | Trigger Control Block | | (e.g, by config) | +-----------------------+ ^ - |(Trigger Control block pointer) | + |(Trigger Control block pointer) + | | +-----------------------+ | LSP Control Block | +-----------------------+ When LSR-B detects a better next hop to LSR-D through LSR-E, and it decides to switch over to it, so control blocks in LSR-B are: +-----------------------+ | LSP Control Block | | (original LSP) | +-----------------------+ (LSP ^ | - Control | | (Next Hop Control Block Pointer) + Control | | (Next Hop Trigger Control Block Pointer) Block | | Pointer) | v +--------------------------------+ | Next Hop Trigger Control Block | +--------------------------------+ ^ | (Trigger | | (New Next Hop LSP Control | | Control Block Pointer) Block | | Pointer)| | @@ -221,27 +222,26 @@ Block | | Pointer)| | | v +------------------------+ | LSP Control Block | | (for LSP: LSR-B, LSR-E,| | LSR-D) | +------------------------+ 3.1.2 States - This section describes the various states that are used in the state machine for the ATM non VC-merge LSR. -- IDLE - This is the initial LSP state, when the LSP_Control_Block is created. + This is the initial LSP state, when the LSP Control Block is created. -- RESPONSE_AWAITED This state means that the LSR has received and processed an LDP- REQUEST from an upstream LSR, or it has received an internal set up request. It has sent a new LDP-REQUEST towards a downstream LSR. The LSR is waiting for the LDP-MAPPING from the downstream LSR. -- ESTABLISHED @@ -302,88 +303,92 @@ -- Internal New NH The LSR decides to switch over the better next hop. 3.1.4 State Transitions The following diagram describes briefly the state transitions. +-------------------+ - | | - +-------->| IDLE |<--------------+ + | |<-------------------+ + +-------->| IDLE | | + | | |----------+ | + | +-------------------+ | | + |(LDP Release) | | | + |(LDP Upstream |(LDP Request 1) | | (LDP Release) + | Abort |(Internal SetUp) | | (Upstream Lost) + |(Internal Destroy) | | | + |(Upstream Lost) v | | + | +-------------------+ | | + +---------| | | | + | RESPONSE_AWAITED | | | + +---------| | | | + | +-------------------+ | | | | | | - | +-------------------+ |(LDP Release) - |(LDP Upstream | | - | Abort) |(LDP Request) |(LDP Upstream Abort) - |(Downstream Lost) |(Internal SetUp) | - |(Downstream NAK) | |(LDP Downstream NAK) - |(Upstream Lost) v |(Upstream Lost) - | +-------------------+ | + |(Downstream Lost) |(LDP Mapping) | | + |(LDP Downstream | | | + | NAK) | +---------------+ | + | | | (LDP Request 2) | | | | | - +---------| RESPONSE_AWAITED | | - | | | - +-------------------+ | - | | - |(LDP Mapping) | - | | - v | - +-------------------+ | + | v v | + | +-------------------+ (LDP Withdraw 1) | + | | | (Internal Destroy) | + | | ESTABLISHED |------------>-------+ + | | | | + | +-------------------+ | | | | - | ESTABLISHED |------------>--+ | | | - +-------------------+ | - | | - | | - |(LDP Withdraw) | - |(Downstream Lost) | - | | - v | - +-------------------+ | + | |(LDP Withdraw 2) | (LDP Upstream + | |(Downstream Lost) | Abort) | | | - | RELEASE_AWAITED |------------>--+ + | v | + | +-------------------+ | + | | | | + +-------->| RELEASE_AWAITED |------------>-------+ | | +-------------------+ 3.1.5 State Machine 3.1.5.1 State -- "IDLE" State: IDLE + Event: LDP Request - New State: Depends upon the action routine + 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, and send an LDP-MAPPING upstream with the - upstream label. + 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 and delete the control - block. + 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. @@ -520,34 +523,35 @@ 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]), and delete the LSP_Control_Block. + (No Label Resources [4]), go to IDLE and delete the LSP Control + Block. State: RESPONSE_AWAITED - Event: LDP Release New State: IDLE Actions: If the LSR uses the independent control mode, free the upstream label. - Send an LDP-ABORT downstream and delete the LSP_Control_Block. + 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 @@ -563,74 +567,75 @@ 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. + Delete the LSP Control Block. State: RESPONSE_AWAITED Event: LDP Downstream NAK - New State: Depends on the action routine + 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. + 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. - Then delete the control block. + 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 and delete the LSP_Control_Block. + 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 + 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. + 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]) and then delete the control block. + (with a status `No Route' [4]), go to IDLE and delete the LSP Control + Block. State: RESPONSE_AWAITED - Event: Internal SetUp New State: RESPONSE_AWAITED Actions: Ignore, it is an internal implementation error. State: RESPONSE_AWAITED @@ -633,21 +638,22 @@ Ignore, it is an internal implementation error. State: RESPONSE_AWAITED Event: Internal Destroy New State: IDLE Actions: - Send an LDP-ABORT downstream and delete the LSP_Control_Block. + Send an LDP-ABORT downstream, go to IDLE and delete the LSP Control + Block. State: RESPONSE_AWAITED Event: Internal Cross-Connect New State: RESPONSE_AWAITED Actions: Ignore the event. It is an internal implementation error. @@ -663,30 +669,30 @@ Send LDP-ABORT to the old downstream, and send LDP-REQUEST to the new next hop. 3.1.5.3 State --"ESTABLISHED" State: ESTABLISHED Event: LDP Request New State: ESTABLISHED - Actions: - Ignore the event. It's an internal implementation error. For non VC- - merge ATM LSR, a new LSP control block is always created for each LDP - request. + Ignore the event. It's an internal implementation error. For non + VC-merge ATM LSR, a new LSP control block is always created for each + LDP request. State: ESTABLISHED Event: LDP Mapping + New State: ESTABLISHED Actions: Process the LDP-MAPPING, which may contain the new attributes of the label mapping and then propagate the LDP-MAPPING upstream. State: ESTABLISHED Event: LDP Release @@ -694,70 +700,70 @@ New State: IDLE Actions: Disconnect the upstream label from the downstream label. Free the upstream label. Free the resources. - Send event `Internal Destroy' to the Next Hop Trigger Block if it was - in the middle of switching over to the better next hop. + Send event `Internal Destroy' to the Next Hop Trigger Control Block + if it was in the middle of switching over to the better next hop. - Propagate the LDP-RELEASE downstream if the LSR is not the end of LSP - and delete the LSP_Control_Block. + Propagate the LDP-RELEASE downstream if the LSR is not the egress for + the LSP, go to IDLE and delete the LSP Control Block. State: ESTABLISHED Event: LDP Withdraw New State: Depends on the action routine. Actions: 1) Free the resources and send LDP-RELEASE downstream. 2) If it is independent control mode, set the state to `IDLE', create - a internal LDP Request with the information in the LSP_Control_Block, + a internal LDP Request with the information in the LSP Control Block, and pass event `LDP Request' to its own state machine. 3) Else for the ordered control mode 3.1)If the LSP is triggered to be setup by itself (e.g it is the - ingress LSR of this LSP), send event `Internal LSP NAK' to the - trigger control block and delete the control block + ingress LSR of this LSP), send event `Internal LSP Down' to the + trigger control block, go to IDLE and delete the LSP Control Block. - 3.2) else, if it is triggered by the incoming LDP Request, + 3.2) Else, if it is triggered by the incoming LDP Request, Disconnect the upstream label from the downstream label. Propagate the LDP-WITHDRAW upstream and go to state `RELEASE_AWAITED'. 3.3) If the LSP is in the middle of switching over to a better LSP, send event `Internal Destroy' to the state machine of its New Next - Hop LSP Control Block. + Hop LSP Control Block, go to IDLE and delete the LSP Control Block. State: ESTABLISHED Event: LDP Upstream Abort - New State: IDLE + New State: ESTABLISHED Actions: - Disconnect the upstream label from the downstream label. - - Free the upstream label. - - Send event `Internal Destroy' if the LSR was in the middle of - switching over to the better next hop. + Ignore the event. - Propagate an LDP-RELEASE downstream and delete the LSP_Control_Block. + Note: This scenario can occur if the upstream LSR sends a LDP-ABORT + at about the same time as the local LSR sends a LDP-MAPPING. In this + situation, it should be up to exactly one of the two LSRs as to + whether or not the label that was sent remains valid. The LDP + specification [4] procedures leave the choice to the upstream LSR + which must send an LDP-RELEASE if it will not use the label provided. State: ESTABLISHED Event: LDP Downstream NAK New State: ESTABLISHED Actions: Ignore the event. It is a protocol error from the downstream LSR. @@ -774,33 +779,34 @@ Disconnect the upstream label from the downstream label. Free the upstream label. Send event `Internal Destroy' to the Next Hop Trigger Control Block if it was in the middle of switching over to the better next hop. Free the resources. - Propagate an LDP-RELEASE downstream and delete the LSP_Control_Block. + Propagate an LDP-RELEASE downstream, go to IDLE and delete the LSP + Control Block. State: ESTABLISHED Event: Downstream Lost - New State: Depends on the actions + 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 NAK' to the Trigger - control block and delete the control block. + control block, go to IDLE and delete the LSP Control Block. 2) Else, disconnect the upstream label from the downstream label. Propagate an LDP-WITHDRAW upstream and go to `RELEASE_AWAITED' state. 3) Send event `Internal Destroy' to the Next Hop Trigger Control Block if it was in the middle of switching over to the better next hop. State: ESTABLISHED @@ -818,21 +824,22 @@ New State: IDLE Actions: Disconnect the upstream label from the downstream label if it is not the ingress of the LSP. Free the resources. - Send an LDP-RELEASE downstream and delete the LSP_Control_Block. + Send an LDP-RELEASE downstream, go to IDLE and delete the LSP Control + Block. State: ESTABLISHED Event: Internal Cross-Connect New State: ESTABLISHED Actions: Connect the upstream label to the downstream label @@ -853,39 +860,39 @@ 1) If the LSR was in the middle of switching over to a better next hop (Next Hop Trigger Control Block Pointer is not zero), it send `Internal New NH' to that control block. 2) Else, create a new Next Hop Trigger Control Block, set Next Hop Trigger Control Block pointer which points this control block. And then pass `Internal New NH' to this control block. 3.1.5.4 State --"RELEASE_AWAITED" - State RELEASE_AWAITED + State: RELEASE_AWAITED - Event LDP Request + Event: LDP Request New State: RELEASE_AWAITED Actions: Ignore the event. It is an internal implementation error. State: RELEASE_AWAITED Event: LDP Mapping New State: RELEASE_AWAITED Actions: - It is an protocol error from the downstream LDP peer, but anyway send + It is a protocol error from the downstream LDP peer, but anyway send a LDP-RELEASE downstream. State: RELEASE_AWAITED Event: LDP Release New State: IDLE Actions: @@ -894,26 +901,25 @@ 2) Delete the control block. State: RELEASE_AWAITED Event: LDP Withdraw New State: RELEASE_AWAITED Actions: - It is an protocol error from the downstream LDP peer, but send a - LDP-RELEASE anyway. + It is a protocol error from the downstream LDP peer, but send a LDP- + RELEASE anyway. State: RELEASE_AWAITED - - Event: LDP Upstream NAK + Event: LDP Upstream Abort New State: IDLE Actions: 1) Free the upstream label 2) Delete the control block. State: RELEASE_AWAITED @@ -1033,47 +1038,50 @@ The LSP through the new next hop could not get set up -- Internal Destroy This event is triggered when the LSR lost the LDP session with its upstream neighbor. 3.1.6.4 State Transition for next hop change - | - | - | - | Internal New NH - | - v +---------------------+ - | | Internal destroy - | NEW_NH_RETRY |-------------- + | | + | IDLE |<------------+ | | | +---------------------+ | | | | | + | (Internal New NH) | + | | + v | + +---------------------+ | + | | | + | NEW_NH_RETRY |----------->-+ + | | (Internal | + +---------------------+ Destroy) | + | | + | | | (Internal retry timeout) | | | v | +---------------------+ | - | | Internal | - | NEW_NH_RESPONSE | Destroy | - | _AWAITED |-------------| + | | (Internal | + | NEW_NH_RESPONSE | Destroy) | + | _AWAITED |----------->-+ | | | +---------------------+ | | | | (Internal LSP UP) | | (Internal LSP NAK) | - v v - the control block is deleted + +------------------------>-+ 3.01.3 State Machine 3.01.3.1 State -- "IDLE" State: IDLE Event: Internal New NH New State: NEW_NH_RETRY @@ -1121,39 +1130,38 @@ Ignore. It is an internal implementation error. 3.01.3.2 State -- "NEW_NH_RETRY" State: NEW_NH_RETRY Event: Internal New NH New State: NEW_NH_RETRY - Actions: Restart the LSP retry timer. State: NEW_NH_RETRY Event: Internal retry timeout - New State: NEW_NH_RESPONSE_AWAITED + New State: Depends on action routine. Actions: - If the new next hop is the same one as the old next hop, delete the - control block. + If the new next hop is the same one as the old next hop, go to IDLE + and delete the control block. Otherwise, create an LSP control block which will try to establish a - new LSP through the new next hop. And send event `Internal Setup' to - its state machine. + new LSP through the new next hop, send event `Internal Setup' to its + state machine and go to NEW_NH_RESPONSE_AWAITED. State: NEW_NH_RETRY Event: Internal LSP UP New State: NEW_NH_RETRY Actions: Ignore. It is an internal implementation error. @@ -1169,23 +1177,24 @@ Ignore. It is an internal implementation error. State: NEW_NH_RETRY Event: Internal destroy New State: IDLE Actions: - Stop the timer and delete the control block. + Stop the timer, go to IDLE and delete the control block. 3.01.3.3 State -- "NEW_NH_RESPONSE_AWAITED" + State: NEW_NH_RESPONSE_AWAITED Event: Internal New NH New State: NEW_NH_RETRY Actions: Restart the LSP retry timer, send `Internal destroy' to the control block of the LSP for the new next hop and go to the `NEW_NH_RETRY' @@ -1208,28 +1217,27 @@ New State: IDLE Actions: Send event `Internal cross-connect' event to the LSP control block of the new next hop. Send event `Internal destroy' event to the original LSP control block. - Then delete the control block. + Then go to IDLE and delete the control block. State: NEW_NH_RESPONSE_AWAITED Event: Internal LSP NAK New State: IDLE - Actions: Delete the control block. State: NEW_NH_RESPONSE_AWAITED Event: Internal destroy New State: IDLE @@ -1236,110 +1244,110 @@ Actions: Send event `Internal destroy' the control block for the new LSP through the new next hop. 3.1.7 LDP Related Message Handling - If an LSR receives an LDP-REQUEST from an upstream LSR: a) If this is a duplicate request, discard the message. A duplicate - request means that there is a LSP_Control_Block which has same FEC, + request means that there is a LSP Control Block which has same FEC, same Upstream Label Request ID and same Upstream LDP Session Identifier. - b) Otherwise, create a new LSP_Control_Block, store the relevant + b) Otherwise, create a new LSP Control Block, store the relevant information from the message into the control block, then pass the event `LDP Request' to its state machine. - If an LSR receives an LDP-MAPPING from a downstream LSR: a) Extract the 'Label Request Message ID' field and from the LDP- MAPPING. - b) Find an LSP_Control_Block which has the same Downstream Label + b) Find an LSP Control Block which has the same Downstream Label Request ID and the same Downstream LDP Session Identifier. - c) If an LSP_Control_Block is found, pass the event `LDP Mapping' to + c) If an LSP Control Block is found, pass the event `LDP Mapping' to its state machine. - d) If there is no matching LSP_Control_Block found, then try to find - an LSP_Control_Block which has the same Downstream Label and the same + d) If there is no matching LSP Control Block found, then try to find + an LSP Control Block which has the same Downstream Label and the same Downstream LDP Session Identifier. - e) If an LSP_Control_Block is found, pass the event `LDP Mapping' to + e) If an LSP Control Block is found, pass the event `LDP Mapping' to its state machine. f) Otherwise, ignore the LDP-MAPPING and send a LDP-RELEASE downstream. - If an LSR receives an LDP-RELEASE from an upstream LSR: - a) Find an LSP_Control_Block which has the same Upstream Label and + a) Find an LSP Control Block which has the same Upstream Label and the same Upstream LDP Session Identifier. - b) If an LSP_Control_Block is found, pass the event `LDP Release' to + b) If an LSP Control Block is found, pass the event `LDP Release' to its state machine. c) Otherwise, ignore the message. - If an LSR receives an LDP-WITHDRAW from a downstream LSR: - a) Find an LSP_Control_Block which has the same Downstream Label and + a) Find an LSP Control Block which has the same Downstream Label and the same Downstream LDP Session Identifier. - b) If an LSP_Control_Block is found, pass the event `LDP Withdraw' to + b) If an LSP Control Block is found, pass the event `LDP Withdraw' to its state machine. c) Otherwise, ignore the LDP-WITHDRAW and send a LDP-RELEASE downstream. - If an upstream LDP peer is lost: - a) Find all the LSP_Control_Blocks whose upstream LDP peer is that + a) Find all the LSP Control Blocks whose upstream LDP peer is that LSR. b) Then pass the event `Upstream Lost' to their state machines. - If a downstream LDP peer is lost: - a) Find all the LSP_Control_Blocks whose downstream LDP peer is that + a) Find all the LSP Control Blocks whose downstream LDP peer is that LSR. b) Then pass the event `Downstream Lost' to their state machines. - If the LSR detects a new next hop for an FEC: For each LSP which needs "local repair", or it needs "global repair" and it is the ingress of the LSP, pass event "Internal New NH" to its state machine. - If an LSR receives an LDP-Abort from an upstream LSR: a) Extract the LDP Request ID value from the LDP-Abort message. - b) Find an LSP_Control_Block which has the same Upstream Label + b) Find an LSP Control Block which has the same Upstream Label Request ID and the same Upstream LDP Session Identifier. - c) If an LSP_Control_Block is found, pass the event `LDP Upstream + c) If an LSP Control Block is found, pass the event `LDP Upstream Abort' to its state machine. d) Otherwise, ignore the message. - If the LSR receives an LDP-NAK from a downstream LSR: a) Extract the LDP Request ID value from the LDP-NAK. - b) Find an LSP_Control_Block which has the same Downstream Label + b) Find an LSP Control Block which has the same Downstream Label Request ID and the same Downstream LDP Session Identifier. - c) If an LSP_Control_Block is found, pass the event `LDP Downstream + c) If an LSP Control Block is found, pass the event `LDP Downstream NAK' to its state machine. d) Otherwise, ignore the message. 3.2. ATM Switch LSR with VC-merge 3.2.1 VC-merge A VC-merge capable LSR can map multiple incoming labels (VPI/VCI) into one outgoing label. It is possible that this LSR can only merge @@ -1350,100 +1358,100 @@ six incoming labels arriving at it for a particular FEC. In this case, this node may merge these into two outgoing labels. When an upstream LSR has a limited merging capability, it is difficult for a downstream LSR to know how many labels should be assigned to each FEC. In this case, downstream-on-demand is recommended. 3.2.2 Control Block - There are 3 types of control blocks involved: - Upstream_LSP_Control_Block, Downstream_LSP_Control_Block, and Next - Hop Trigger Control Block. + There are 3 types of control blocks involved: Upstream LSP Control + Block, Downstream LSP Control Block, and Next Hop Trigger Control + Block. - There is one Upstream_LSP_Control_Block for each LDP-REQUEST + There is one Upstream LSP Control Block for each LDP-REQUEST received. - There is one Downstream_LSP_Control_Block for each unique LDP-REQUEST - sent to a downstream LSR. There can be multiple - Downstream_LSP_Control_Blocks per FEC in an LSR. This can be the - result of an upstream LSR asking for a label for an FEC. This LSR - must assign a unique upstream label and it can not merge this - upstream label into an existing downstream label for this FEC. + There is one Downstream LSP Control Block for each unique LDP-REQUEST + sent to a downstream LSR. There can be multiple Downstream LSP + Control Blocks per FEC in an LSR. This can be the result of an + upstream LSR asking for a label for an FEC. This LSR must assign a + unique upstream label and it can not merge this upstream label into + an existing downstream label for this FEC. There is one Next Hop Trigger Control Block for each FEC for which a better next hop has been detected and the LSR has decided to switch to this better next hop. It could be the result of "local repair" or "global repair" if the LSR is the ingress LSR of the LSP. - A Downstream_LSP_Control_Block contains a list of pointers to - Upstream_LSP_Control_Blocks or the Next Hop Trigger Control Block. + A Downstream LSP Control Block contains a list of pointers to + Upstream LSP Control Blocks or the Next Hop Trigger Control Block. This means that this LSR has decided to map the multiple labels - listed in the Upstream_LSP_Control_Blocks and the Next Hop Trigger - Control Block into a single label listed in the - Downstream_LSP_Control_Block. + listed in the Upstream LSP Control Blocks and the Next Hop Trigger + Control Block into a single label listed in the Downstream LSP + Control Block. - An Upstream_LSP_Control_Block may contain the following information: + An Upstream LSP Control Block may contain the following information: - Upstream LDP Session Identifier - State - Upstream Label (assigned by this LSR) - - Downstream_LSP_Control_Block pointer + - Downstream LSP Control Block pointer - Upstream LDP Request ID (assigned by the upstream LSR in downstream-on-demand mode) - Next_Hop_Trigger_Block pointer Upstream Label and Upstream LDP Session Identifier can be used to - locate a unique Upstream_LSP_Control_Block. + locate a unique Upstream LSP Control Block. If an LSR is using downstream-on-demand mode, it can use the Upstream LDP Request ID and the Upstream LDP Session Identifier to locate a - unique Upstream_LSP_Control_Block. + unique Upstream LSP Control Block. - An Next_Hop_Trigger_LSP_Control_Block may contain the following + An Next_Hop_Trigger LSP Control Block may contain the following information: - - Upstream_LSP_Control_Block pointer, which points to the one + - Upstream LSP Control Block pointer, which points to the one which is needed to switch over to the better next hop - State + - Downstream LSP Control Block pointer - - Downstream_LSP_Control_Block pointer - - A Downstream_LSP_Control_Block may contain the following information: + A Downstream LSP Control Block may contain the following information: - FEC + - State - Downstream LDP Session Identifier - - list of pointers to the Upstream_LSP_Control_Blocks or the + - list of pointers to the Upstream LSP Control Blocks or the Trigger_Control_Blocks which are merged at this LSR for this FEC - Downstream Label (assigned by the downstream LSR) - Downstream Label Request ID (assigned by the LSR itself if it is using downstream-on-demand mode) Downstream Label, Downstream LDP Session Identifier can be used to - locate a unique Downstream_LSP_Control_Block. + locate a unique Downstream LSP Control Block. If an LSR is using downstream-on-demand mode, it can also use the Downstream Label Request ID and the Downstream LDP Session Identifier - to locate a unique Downstream_LSP_Control_Block. + to locate a unique Downstream LSP Control Block. The following diagram details the relationship between these 2 types of control blocks: For example, the LSR has decided to merge 3 LDP-REQUESTs of a FEC from upstream LSR1, LSR2, LSR3 into one LDP-REQUEST and sent it to a downstream LSR4. +---------------------+ | | @@ -1452,32 +1460,32 @@ | LSR1 | | +---------------------+ | | +---------------------+ | | | | | Upstream_LSP_Control| | (merged into) | _Block for Upstream |------+ | LSR2 | | +---------------------+ | +------------------------------+ | | | - +---------------------+ +--->| Downstream_LSP_Control_Block | + +---------------------+ +--->| Downstream LSP Control Block | | Next_Hop_Trigger_ | | | for Downstream LSR4 | - | LSP_Control_Block |------+ | | + | LSP Control Block |------+ | | | | +------------------------------+ +---------------------+ 3.2.3 State Machines for Downstream-on-demand Mode The following sections describe the state machines used in downstream-on-demand mode. -3.2.3.1 State of the Upstream_LSP_Control_Block's State Machine +3.2.3.1 State of the Upstream LSP Control Block's State Machine for Downstream-on-demand Mode -- IDLE This is the initial LSP state. -- RESPONSE_AWAITED This state means that the LSR has received and processed an LDP- REQUEST from an upstream LSR, and has sent a new LDP-REQUEST towards @@ -1483,117 +1491,116 @@ REQUEST from an upstream LSR, and has sent a new LDP-REQUEST towards a downstream LSR. The LSR is waiting for the LDP-MAPPING from the downstream LSR. -- ESTABLISHED This state means that the LSR has received the LDP-MAPPING from the downstream LSR and the LSP is up and operational. -- RELEASE_AWAITED - This state means that the LSR has sent a LDP-WITHDRAW upstream and is waiting for the LDP-RELEASE before freeing up the label resource. -3.2.3.2 Events of the Upstream_LSP_Control_Block's State Machine +3.2.3.2 Events of the Upstream LSP Control Block's State Machine for Downstream-on-demand Mode -- LDP Request The LSR receives an LDP-REQUEST from an upstream LSR. -- Internal Downstream Mapping - This event is sent by one Downstream_LSP_Control_Block's state - machine. This Downstream_LSP_Control_Block is the merged - Downstream_LSP_Control_Block of this Upstream_LSP_Control_Block. The - event is the result of receiving an LDP-MAPPING by the - Downstream_LSP_Control_Block's state machine. + This event is sent by one Downstream LSP Control Block's state + machine. This Downstream LSP Control Block is the merged Downstream + LSP Control Block of this Upstream LSP Control Block. The event is + the result of receiving an LDP-MAPPING by the Downstream LSP Control + Block's state machine. -- LDP Release + The LSR receives an LDP-RELEASE from an upstream LSR. -- Internal Downstream Withdraw - This event is sent by one Downstream_LSP_Control_Block's state - machine. This Downstream_LSP_Control_Block is the merged - Downstream_LSP_Control_Block of this Upstream_LSP_Control_Block. The - event is the result of receiving an LDP-WITHDRAW by the - Downstream_LSP_Control_Block's state machine. + This event is sent by one Downstream LSP Control Block's state + machine. This Downstream LSP Control Block is the merged Downstream + LSP Control Block of this Upstream LSP Control Block. The event is + the result of receiving an LDP-WITHDRAW by the Downstream LSP Control + Block's state machine. -- LDP Upstream Abort The LSR receives an LDP-ABORT from an upstream LSR. -- Internal Downstream NAK - This event is sent by one Downstream_LSP_Control_Block's state - machine. This Downstream_LSP_Control_Block is the merged - Downstream_LSP_Control_Block of this Upstream_LSP_Control_Block. The - event is the result of receiving an LDP-NAK by the - Downstream_LSP_Control_Block's state machine, or it detects an error. + This event is sent by one Downstream LSP Control Block's state + machine. This Downstream LSP Control Block is the merged Downstream + LSP Control Block of this Upstream LSP Control Block. The event is + the result of receiving an LDP-NAK by the Downstream LSP Control + Block's state machine, or it detects an error. -- Upstream Lost The LSR loses the LDP session with its upstream LDP peer. -- Internal New NH - The LSR detects there is better next hop and decides to establish the lsp through this better next hop -- Internal Re-Cross-Connect This event is used to trigger splicing into a different downstream LSP. This can happens when it is switched over to a better LSP through the new next hop. -3.2.3.3 State Transitions of the Upstream_LSP_Control_Block's State +3.2.3.3 State Transitions of the Upstream LSP Control Block's State Machine for Downstream-on-demand Mode +-------------------+ | | - +-------->| IDLE |<------------+ + +-------->| IDLE |<-------------------+ | | | | | +-------------------+ | |(LDP Abort) | | |(Internal |(LDP Request) | | Downstream NAK) | | - |(Upstream Lost) | | - | v | + |(Upstream Lost) | (Upstream Lost) | + | v (LDP Release) | | +-------------------+ | | | | | +---------| RESPONSE_AWAITED | | - | | |(Upstream Lost) + | | | +-------------------+ | | | |(Internal Downstream | - | mapping) |(LDP Release) + | mapping) | | | v | +-------------------+ | - | | |(LDP Abort) - | ESTABLISHED |------->-----+ + | | | + | ESTABLISHED |------->------------+ | | | +-------------------+ | | | | | - |(Internal Downstream Withdraw) - |(Internal Downstream NAK) - v - +-------------------+ | - | | | - |RELEASE_AWAITED |------->-----+ + |(Internal Downstream Withdraw) | + |(Internal Downstream NAK) | + v | + +-------------------+ (LDP Upstream | + | | Abort) | + |RELEASE_AWAITED |------->------------+ | | +-------------------+ -3.2.3.4 Upstream_LSP_Control_Block's State Machine +3.2.3.4 Upstream LSP Control Block's State Machine for Downstream-on-demand Mode 3.2.3.4.1 State -- "IDLE" State: IDLE Event: LDP Request New State: Depends upon the action routine. Actions: @@ -1602,41 +1609,41 @@ Then: choose an upstream label, allocate the resources, connect this upstream label to the local IP forwarding module, send an LDP- MAPPING upstream with the upstream label and go to the state `ESTABLISHED'. else - Obtain a next hop (or interface). Find a - Downstream_LSP_Control_Block which has the same FEC and the same - next hop and also is able to merge more input labels. If not found, - create a new Downstream_LSP_Control_Block with the state `IDLE'. + Obtain a next hop (or interface). Find a Downstream LSP Control + Block which has the same FEC and the same next hop and also is able + to merge more input labels. If not found, create a new Downstream + LSP Control Block with the state `IDLE'. - If the state of the Downstream_LSP_Control_Block is `ESTABLISHED', + If the state of the Downstream LSP Control Block is `ESTABLISHED', choose an upstream label, connect the upstream label with the downstream label and send an LDP-MAPPING upstream with the upstream label, and go to the state `ESTABLISHED'. - If the state of Downstream_LSP_Control_Block is not `ESTABLISHED', - set the state of the Upstream_LSP_Control_Block to + If the state of Downstream LSP Control Block is not `ESTABLISHED', + set the state of the Upstream LSP Control Block to `RESPONSE_AWAITED'. If the LSR use the independent control mode [2], choose an upstream label, and send an LDP-MAPPING upstream. - Pass the event `Internal AddUpstream' to the - Downstream_LSP_Control_Block's state machine. + Pass the event `Internal AddUpstream' to the Downstream LSP Control + Block's state machine. If unable to process the request for any reason, issue an LDP-NAK to - the sender with the appropriate error code and delete the control - block. + the sender with the appropriate error code, go to IDLE and delete the + control block. State: IDLE Event: Internal Downstream Mapping New State: IDLE Actions: Ignore the event. It is an internal implementation error. @@ -1719,45 +1726,42 @@ New State: RESPONSE_AWAITED Actions: Ignore the event. It is an internal implementation error. State: RESPONSE_AWAITED Event: Internal Downstream Mapping - New State: Depends on the action routine + New State: Depends on the action routine. Actions: - If the LSR uses the ordered control mode, assign an upstream label. - - Connect the upstream label to the downstream label and allocate the - resources. - - Send an LDP-MAPPING upstream with the upstream label. - - Then go to the state `ESTABLISHED'. + If the LSR uses the ordered control mode, assign an upstream label, + connect the upstream label to the downstream label and allocate the + resources, send an LDP-MAPPING upstream with the upstream label and + go to `ESTABLISHED'. If unable to process the message for any reason, issue an LDP-NAK - upstream and an LDP-RELEASE downstream and delete the control block. + upstream and an LDP-RELEASE downstream, go to IDLE and delete the + control block. State: RESPONSE_AWAITED Event: LDP Release New State: RESPONSE_AWAITED Actions - Ignore the event. It is an protocol error from the upstream peer. + Ignore the event. It is a protocol error from the upstream peer. State: RESPONSE_AWAITED Event: Internal Downstream Withdraw New State: RESPONSE_AWAITED Actions Ignore the event. It is an internal implementation error. @@ -1766,30 +1770,30 @@ Event: LDP Upstream Abort New State: IDLE Actions If the LSR uses the independent control mode, free the upstream label and the resources. - Send the event `Internal DeleteUpstream' to its - Downstream_LSP_Control_Block's state machine. + Send the event `Internal DeleteUpstream' to its Downstream LSP + Control Block's state machine. Delete the control block. State: RESPONSE_AWAITED + Event: Internal Downstream NAK New State: IDLE - Actions: If the LSR uses the independent control mode, free the upstream label and the resources. Then, send an LDP-WITHDRAW upstream. If the LSR uses the ordered control mode, propagate the LDP-NAK upstream. Delete the control block. @@ -1797,22 +1801,22 @@ Event: Upstream Lost New State: IDLE Actions If the LSR uses the independent control mode, free the upstream label and the resources. - Send the event `Internal DeleteUpstream' to its - Downstream_LSP_Control_Block's state machine. + Send the event `Internal DeleteUpstream' to its Downstream LSP + Control Block's state machine. Delete the control block. State: RESPONSE_AWAITED Event: Internal Re-Cross-Connect New State: RESPONSE_AWAITED Actions: @@ -1823,36 +1827,36 @@ Event: Internal New NH New State: depends on the actions Actions: Send event `Internal DeleteUpstream' to its old downstream control block. - Find a Downstream_LSP_Control_Block which has the same FEC and the + Find a Downstream LSP Control Block which has the same FEC and the same next hop and also is able to merge more input labels. If not - found, create a new Downstream_LSP_Control_Block with the state + found, create a new Downstream LSP Control Block with the state `IDLE'. - If the state of the Downstream_LSP_Control_Block is `ESTABLISHED', + If the state of the Downstream LSP Control Block is `ESTABLISHED', choose an upstream label, connect the upstream label with the downstream label and send an LDP-MAPPING upstream with the upstream label, and go to the state `ESTABLISHED'. - If the state of Downstream_LSP_Control_Block is not `ESTABLISHED', - set the state of the Upstream_LSP_Control_Block to + If the state of Downstream LSP Control Block is not `ESTABLISHED', + set the state of the Upstream LSP Control Block to `RESPONSE_AWAITED'. - Pass the event `Internal AddUpstream' to the new - Downstream_LSP_Control_Block's state machine. + Pass the event `Internal AddUpstream' to the new Downstream LSP + Control Block's state machine. 3.2.3.4.3 State -- "ESTABLISHED" State: ESTABLISHED Event: LDP Request New State: ESTABLISHED Actions @@ -1866,82 +1870,79 @@ New State: ESTABLISHED Actions Process the new attributes of the mapping and then propagate the LDP-MAPPING upstream. State: ESTABLISHED Event: LDP Release + New State: IDLE Actions - Disconnect the upstream label from the downstream label, free the upstream label and resources. - Send the event `Internal DeleteUpstream' to its - Downstream_LSP_Control_Block's state machine. + Send the event `Internal DeleteUpstream' to its Downstream LSP + Control Block's state machine. Send the event `Internal Destroy' to the Next_Hop_Trigger_Block's state machine if the LSR was in the middle of switching over to the better next hop. Delete the control block. State: ESTABLISHED Event: Internal Downstream Withdraw - New State: Depends on the action routine + New State: Depends on the action routine. Actions If it uses independent mode, set its state to `IDLE' and create a internal `LDP Request' and send to its own state machine. Else Disconnect the upstream label from the downstream label. Propagate the LDP-WITHDRAW upstream and go to state `RELEASE_AWAITED'. Send the event `Internal Destroy' to the Next_Hop_Trigger_Block's state machine if the LSR was in the middle of switching over to the better next hop. State: ESTABLISHED Event: LDP Upstream Abort - New State: IDLE + New State: ESTABLISHED Actions - Disconnect the upstream label from the downstream label, free the - upstream label and the resources. - - Send the event `Internal DeleteUpstream' to its - Downstream_LSP_Control_Block's state machine. - - Send the event `Internal Destroy' to the Next_Hop_Trigger_Block's - state machine if the LSR was in the middle of switching over to the - better next hop. + Ignore the event. - Delete the control block. + Note: This scenario can occur if the upstream LSR sends a LDP-ABORT + at about the same time as the local LSR sends a LDP-MAPPING. In this + situation, it should be up to exactly one of the two LSRs as to + whether or not the label that was sent remains valid. The LDP + specification [4] procedures leave the choice to the upstream LSR + which must send an LDP-RELEASE if it will not use the label provided. State: ESTABLISHED Event: Internal Downstream NAK - New State: Depends on the actions + New State: Depends on the action routine. Actions: If it uses independent mode, set its state to `IDLE' and create a internal `LDP Request' and send to its own state machine. Else Disconnect the upstream label from the downstream label Send an LDP-WITHDRAW upstream and go to state `RELEASE_AWAITED'. @@ -1954,22 +1955,22 @@ Event: Upstream Lost New State: IDLE Actions: Disconnect the upstream label from the downstream label, free the upstream label and the resources. - Send the event `Internal DeleteUpstream' to its - Downstream_LSP_Control_Block's state machine. + Send the event `Internal DeleteUpstream' to its Downstream LSP + Control Block's state machine. Send the event `Internal Destroy' to the Next_Hop_Trigger_Block's state machine if the LSR was in the middle of switching over to the better next hop. Delete the control block. State: ESTABLISH Event: Internal Re-Cross-Connect @@ -1968,27 +1969,26 @@ state machine if the LSR was in the middle of switching over to the better next hop. Delete the control block. State: ESTABLISH Event: Internal Re-Cross-Connect New State: ESTABLISH - Actions: Reconnect the upstream label to the new downstream label. - Send the event `Internal DeleteUpstream' to its old - Downstream_LSP_Control_Block's state machine. + Send the event `Internal DeleteUpstream' to its old Downstream LSP + Control Block's state machine. State: ESTABLISH Event: Internal New NH New State: ESTABLISH Actions: Create a new Next_Hop_Trigger_Control_Block and pass event `Internal @@ -2078,54 +2078,53 @@ State: RELEASE_AWAITED Event: Internal Re-Cross-Connect New State: RELEASE_AWAITED Actions: Ignore the event. It is an internal implementation error. -3.2.3.5 State of the Downstream_LSP_Control_Block's State Machine +3.2.3.5 State of the Downstream LSP Control Block's State Machine for Downstream-on-demand Mode -- IDLE This is the initial LSP state. -- RESPONSE_AWAITED This state means that the LSR has received an LDP-REQUEST from an upstream LSR, has processed the LDP-REQUEST, and has sent a new LDP- REQUEST towards a downstream LSR. The LSR is waiting for the LDP- MAPPING from the downstream LSR. -- ESTABLISHED This state means that the LSR has received the LDP-MAPPING from the downstream LSR and the LSP is up and operational. -3.2.3.6 Events of the Downstream_LSP_Control_Block's State Machine +3.2.3.6 Events of the Downstream LSP Control Block's State Machine for Downstream-on-demand Mode -- Internal AddUpstream - This event is sent by an Upstream_LSP_Control_Block's state machine + This event is sent by an Upstream LSP Control Block's state machine when it is created. -- Internal DeleteUpstream - This event is sent by an Upstream_LSP_Control_Block's state machine + This event is sent by an Upstream LSP Control Block's state machine when it is deleted. -- LDP Mapping - The LSR receives an LDP-MAPPING from a downstream LSR. -- LDP Withdraw The LSR receives an LDP-WITHDRAW from a downstream LSR. -- LDP Downstream NAK The LSR receives an LDP-NAK from a downstream LSR. @@ -2126,61 +2125,60 @@ The LSR receives an LDP-WITHDRAW from a downstream LSR. -- LDP Downstream NAK The LSR receives an LDP-NAK from a downstream LSR. -- Downstream Lost The LSR loses the LDP session with its downstream LSR. -3.2.3.7 State Transitions of the Downstream_LSP_Control_Block's +3.2.3.7 State Transitions of the Downstream LSP Control Block's State Machine for Downstream-on-demand mode +-------------------+ | | | IDLE |<--------------+ | | |(last Internal +-------------------+ | DeleteUpstream) | |(LDP Withdraw) |(1st Internal AddUpstream)| | |(LDP Downstream v | NAK) +-------------------+ |(Downstream | | | Lost) - | RESPONSE_AWAITED |---------->----^ + | RESPONSE_AWAITED |---------->----+ | | | +-------------------+ | | | |(LDP Mapping) | | | v | +-------------------+ | | | | - | ESTABLISHED |-------->------^ + | ESTABLISHED |-------->------+ | | +-------------------+ -3.2.3.8 Downstream_LSP_Control_Block's State Machine for +3.2.3.8 Downstream LSP Control Block's State Machine for Downstream-on-demand Mode. 3.2.3.8.1 State -- "IDLE" - State: IDLE Event: Internal AddUpstream New State: RESPONSE_AWAITED Actions - Initialize the list of pointers in the Upstream_LSP_Control_Block to + Initialize the list of pointers in the Upstream LSP Control Block to contain the newly added upstream pointer. Send a new LDP-REQUEST downstream and go to the state `RESPONSE_AWAITED'. State: IDLE Event: Internal DeleteUpstream New State: IDLE @@ -2231,46 +2229,45 @@ 3.2.3.8.2 State -- "RESPONSE_AWAITED" State: RESPONSE_AWAITED Event: Internal AddUpstream New State: RESPONSE_AWAITED Actions - Add the pointer to new Upstream_LSP_Control_Block to the - Upstream_LSP_Control_Blocks pointer list. + Add the pointer to new Upstream LSP Control Block to the Upstream LSP + Control Blocks pointer list. State: RESPONSE_AWAITED Event: Internal DeleteUpstream New State: Depend on the action routine Actions - Delete the Upstream_LSP_Control_Block pointer from the - Upstream_LSP_Control_Block pointers list. + Delete the Upstream LSP Control Block pointer from the Upstream LSP + Control Block pointers list. If the list becomes empty, release the resources, send an LDP-Abort - downstream, and then delete the control block. + downstream, go to IDLE and then delete the control block. State: RESPONSE_AWAITED Event: LDP Mapping New State: ESTABLISHED - Actions - For each Upstream_LSP_Control_Block in the Upstream_LSP_Control_Block + For each Upstream LSP Control Block in the Upstream LSP Control Block pointers list, pass the event `Internal Downstream Mapping' to its state machine. State: RESPONSE_AWAITED Event: LDP Withdraw New State: RESPONSE_AWAITED Actions @@ -2278,87 +2276,89 @@ RELEASE downstream State: RESPONSE_AWAITED Event: LDP Downstream NAK New State: IDLE Actions - For each Upstream_LSP_Control_Block in the Upstream_LSP_Control_Block + For each Upstream LSP Control Block in the Upstream LSP Control Block pointers list, pass the event `Internal Downstream NAK' to its state machine. Release the resources, and delete the control block. State: RESPONSE_AWAITED Event: Downstream Lost New State: IDLE Actions - For each Upstream_LSP_Control_Block in the Upstream_LSP_Control_Block + For each Upstream LSP Control Block in the Upstream LSP Control Block pointers list, pass the event `Internal Downstream NAK' to its state machine. Release the resources, and delete the control block. 3.2.3.8.3 State -- "ESTABLISHED" State: ESTABLISHED - Event: Internal AddUpstream New State: ESTABLISHED Actions - Add the pointer to new Upstream_LSP_Control_Block to the - Upstream_LSP_Control_Block pointers list. + Add the pointer to new Upstream LSP Control Block to the Upstream LSP + Control Block pointers list. State: ESTABLISHED Event: Internal DeleteUpstream - New State: Depends on the action routine + + New State: Depends on the action routine. Actions - Delete the pointer of Upstream_LSP_Control_Block from its - Upstream_LSP_Control_Block pointers list. + Delete the pointer of Upstream LSP Control Block from its Upstream + LSP Control Block pointers list. If the list becomes empty, release the resources, send an LDP-RELEASE - downstream, and then delete the control block. + downstream, go to IDLE and then delete the control block. + + Otherwise, remain in the ESTABLISHED state. State: ESTABLISHED Event: LDP Mapping New State: ESTABLISHED Actions - For each Upstream_LSP_Control_Block in the Upstream_LSP_Control_Block + For each Upstream LSP Control Block in the Upstream LSP Control Block pointers list, pass the event `Internal Downstream mapping' to its state machine. State: ESTABLISHED Event: LDP Withdraw New State: IDLE Actions - For each Upstream_LSP_Control_Block in the Upstream_LSP_Control_Block + For each Upstream LSP Control Block in the Upstream LSP Control Block pointers list, pass the event `Internal Downstream withdraw' to its state machine. Release the resources, and delete the control block and send LDP- RELEASE downstream. State: ESTABLISHED Event: LDP Downstream NAK @@ -2388,69 +2388,71 @@ 3.2.3.10 Events of the Next_Hop_Trigger_Control_Block's State Machine for Downstream-on-demand Mode -- Internal New NH Trigger to setup an LSP through a better next hop. -- Internal Downstream Mapping - This event is sent by one Downstream_LSP_Control_Block's state - machine. This Downstream_LSP_Control_Block is the merged - Downstream_LSP_Control_Block of this Upstream_LSP_Control_Block. The - event is the result of receiving an LDP-MAPPING by the - Downstream_LSP_Control_Block's state machine. + This event is sent by one Downstream LSP Control Block's state + machine. This Downstream LSP Control Block is the merged Downstream + LSP Control Block of this Upstream LSP Control Block. The event is + the result of receiving an LDP-MAPPING by the Downstream LSP Control + Block's state machine. -- Internal Downstream NAK - - This event is sent by one Downstream_LSP_Control_Block's state - machine. This Downstream_LSP_Control_Block is the merged - Downstream_LSP_Control_Block of this Upstream_LSP_Control_Block. The - event is the result of receiving an LDP-NAK by the - Downstream_LSP_Control_Block's state machine, or it detects an error. + This event is sent by one Downstream LSP Control Block's state + machine. This Downstream LSP Control Block is the merged Downstream + LSP Control Block of this Upstream LSP Control Block. The event is + the result of receiving an LDP-NAK by the Downstream LSP Control + Block's state machine, or it detects an error. -- Internal Destroy This event is used to stop the procedure of switching over to the better next hop. 3.2.3.11 State Transitions of the Next_Hop_Trigger_Control_Block's State Machine for Downstream-on-demand Mode - | - | - | - | Internal New NH - | - v +---------------------+ - | | Internal destroy - | NEW_NH_RETRY |-------------- + | | + | IDLE |<------------+ | | | +---------------------+ | | | | | + | (Internal New NH) | + | | + v | + +---------------------+ | + | | | + | NEW_NH_RETRY |----------->-+ + | | (Internal | + +---------------------+ Destroy) | + | | + | | | (Internal retry timeout) | | | v | +---------------------+ | - | | Internal | - | NEW_NH_RESPONSE | Destroy | - | _AWAITED |-------------| + | | (Internal | + | NEW_NH_RESPONSE | Destroy) | + | _AWAITED |----------->-+ | | | +---------------------+ | | | | (Internal Downstream | | Mapping | | (Internal Downstream | | NAK) | - v v - the control block is deleted + +------------------------>-+ 3.2.3.12 State Machine 3.2.3.12.1 State -- "IDLE" State: IDLE Event: Internal New NH New State: NEW_NH_RETRY @@ -2499,38 +2500,40 @@ Ignore. It is an internal implementation error. 3.2.3.12.2 State -- "NEW_NH_RETRY" State: NEW_NH_RETRY Event: Internal New NH New State: NEW_NH_RETRY + Actions: Restart the LSP retry timer. State: NEW_NH_RETRY Event: Internal retry timeout - New State: NEW_NH_RESPONSE_AWAITED + New State: Depends on the action routine. Actions: - If the new next hop is the same one as the old next hop, delete the - control block. + If the new next hop is the same one as the old next hop, go to IDLE + and delete the control block. - Otherwise, find an downstream LSP control block which go through the - same next hop for the same FEC, if there is no one, create one, and - pass `Internal AddUpstream' event to its state machine. + Otherwise, go to NEW_NH_RESPONSE_AWAITED, find an downstream LSP + control block which go through the same next hop for the same FEC, if + there is no one, create one, and pass `Internal AddUpstream' event to + its state machine. State: NEW_NH_RETRY Event: Internal Downstream Mapping New State: NEW_NH_RETRY Actions: Ignore. It is an internal implementation error. @@ -2558,23 +2560,22 @@ 3.2.3.12.3 State -- "NEW_NH_RESPONSE_AWAITED" State: NEW_NH_RESPONSE_AWAITED Event: Internal New NH New State: NEW_NH_RETRY Actions: - Restart the LSP retry timer, send `Internal destroy' to the control - block of the LSP for the new next hop and go to the `NEW_NH_RETRY' - state. + Restart the LSP retry timer and send event `Internal destroy' to the + control block of the LSP for the new next hop. State: NEW_NH_RESPONSE_AWAITED Event: Internal retry timeout New State: NEW_NH_RESPONSE_AWAITED Actions: Ignore. It is an internal implementation error. @@ -2587,27 +2588,28 @@ Actions: Send event `Internal Re-cross-connect' event to the upstream LSP control block of the new next hop. Send event `DeleteUpstream' event to the downstream LSP control block of the the new next hop, since the upstream has spliced into the new next hop. - Then delete the control block. + Delete the control block. State: NEW_NH_RESPONSE_AWAITED Event: Internal Downstream NAK New State: IDLE + Actions: Delete the control block. State: NEW_NH_RESPONSE_AWAITED Event: Internal destroy New State: IDLE @@ -2614,76 +2616,76 @@ Actions: Send event `Internal DeleteUpstream' the control block for the new LSP through the new next hop. 3.2.4 LDP Related Message Processing - If an LSR receives an LDP-REQUEST: a) If this is a duplicate request, discard the message. A duplicate - request means that there is a LSP_Control_Block which has same FEC, + request means that there is a LSP Control Block which has same FEC, same Upstream Label Request ID and same Upstream LDP Session Identifier. - b) Otherwise, create a new Upstream_LSP_Control_Block. Then pass the - event `LDP Request' to this Upstream_LSP_Control_Block's state + b) Otherwise, create a new Upstream LSP Control Block. Then pass the + event `LDP Request' to this Upstream LSP Control Block's state machine. - If an LSR receives an LDP-MAPPING: - Locate a Downstream_LSP_Control_Block which has the same FEC, the + Locate a Downstream LSP Control Block which has the same FEC, the same Downstream LDP Session Identifier and the same Downstream Label. - If a Downstream_LSP_Control_Block is found, pass the event `LDP + If a Downstream LSP Control Block is found, pass the event `LDP Mapping' to its state table. This could mean that the attributes of label binding have changed. Otherwise, use the Downstream LDP request ID (the 'Label Request Message ID' field in the LDP-MAPPING) and Downstream LDP Session - Identifier to locate the Downstream_LSP_Control_Block and pass the - event `LDP Mapping' to its state machine. If no - Downstream_LSP_Control_Block is found, ignore the message. + Identifier to locate the Downstream LSP Control Block and pass the + event `LDP Mapping' to its state machine. If no Downstream LSP + Control Block is found, ignore the message. - If an LSR receives an LDP-RELEASE: - Locate an Upstream_LSP_Control_Block which has the same FEC, the same + Locate an Upstream LSP Control Block which has the same FEC, the same Upstream Label, the same Upstream LDP Session Identifier. If no - Upstream_LSP_Control_Block is found, ignore the message. If an - Upstream_LSP_Control_Block is found, send the event `LDP Release' to + Upstream LSP Control Block is found, ignore the message. If an + Upstream LSP Control Block is found, send the event `LDP Release' to its state machine. - If an LSR receives an LDP-WITHDRAW: - Find a Downstream_LSP_Control_Block which has the same FEC, the same - Downstream LDP Session Identifier and the same Downstream Label. Pass - the event `LDP Withdraw' to its state machines. + Find a Downstream LSP Control Block which has the same FEC, the same + Downstream LDP Session Identifier and the same Downstream Label. + Pass the event `LDP Withdraw' to its state machines. - If an Upstream LDP peer is lost: Pass the event `Upstream Lost' to the state machines of all the - Upstream_LSP_Control_Blocks whose upstream LDP peer is that LSR. + Upstream LSP Control Blocks whose upstream LDP peer is that LSR. - If a Downstream LDP peer is lost: Pass the event `Downstream Lost' to the state machines of all the - Downstream_LSP_Control_Blocks whose the downstream LDP peer is that + Downstream LSP Control Blocks whose the downstream LDP peer is that LSR. - If a next hop of an FEC is changed: - For all the Upstream_LSP_Control_Blocks which are infected by this + For all the Upstream LSP Control Blocks which are infected by this change, pass the event `Internal New NH' to their state machines. - If an LSR receives an LDP-ABORT from an upstream LSR: Use the Upstream LDP Request ID and Upstream LDP Session Identifier - to locate the Upstream_LSP_Control_Block and pass the event `LDP + to locate the Upstream LSP Control Block and pass the event `LDP Abort' to its state machine. - If an LSR receives an LDP-NAK from a downstream LSR: Use the Downstream LDP Request ID and Downstream Session Identifier to locate a Downstream_LSP_control_block and pass the event `LDP Downstream NAK' to its state machine. 4. State Machine for Downstream Unsolicited @@ -2695,50 +2697,50 @@ independent LSP control mode uses the liberal label retention mode and so is considered burning too many ATM resources. In downstream unsolicited mode, multiple path is not supported in this version and will be For Further Study (FFS). We suspect with multiple next hops and Downstream mode, it is easy to get into a loop condition. 4.0 Control Block - There are 2 types of control blocks involved: - Upstream_LSP_Control_Block, Downstream_LSP_Control_Block. + There are 2 types of control blocks involved: Upstream LSP Control + Block, Downstream LSP Control Block. - There is a list of Upstream_LSP_Control_Blocks for each FEC in the - routing table, with each one corresponding to a LDP peer. A - Upstream_LSP_Control_Block is created for each FEC when there is a - label ready to be distributed to that upstream. It is deleted when - the FEC is deleted from the FEC table, or the LDP peer disappears, or - the downstream label is withdrawed. + There is a list of Upstream LSP Control Blocks for each FEC in the + routing table, with each one corresponding to a LDP peer. A Upstream + LSP Control Block is created for each FEC when there is a label ready + to be distributed to that upstream. It is deleted when the FEC is + deleted from the FEC table, or the LDP peer disappears, or the + downstream label is withdrawed. - There is one Downstream_LSP_Control_Blocks for each FEC in the + There is one Downstream LSP Control Blocks for each FEC in the routing table. It is created when the FEC is inserted into the forwarding table and deleted when the FEC is removed from the forwarding table. - An Upstream_LSP_Control_Block may contain the following information: + An Upstream LSP Control Block may contain the following information: - Upstream LDP Session Identifier - State - Upstream Label (assigned by this LSR) - FEC Upstream Label and Upstream LDP Session Identifier, or FEC and Upstream LDP Session Identifier can be used to locate a unique - Upstream_LSP_Control_Block. + Upstream LSP Control Block. - A Downstream_LSP_Control_Block may contain the following information: + A Downstream LSP Control Block may contain the following information: - FEC - State - Downstream LDP Session Identifier - Downstream Label (assigned by the downstream LSR) - Downstream Label Request ID (assigned by the LSR itself) @@ -2735,80 +2737,81 @@ - FEC - State - Downstream LDP Session Identifier - Downstream Label (assigned by the downstream LSR) - Downstream Label Request ID (assigned by the LSR itself) + Downstream Label and Downstream LDP Session Identifier, or FEC and Downstream LDP Session Identifier can be used to locate a unique - Downstream_LSP_Control_Block. + Downstream LSP Control Block. -4.1 States of the Upstream_LSP_Control_Block's State Machine +4.1 States of the Upstream LSP Control Block's State Machine for Downstream Mode -- IDLE This is the initial LSP state. -- ESTABLISHED This state means that the LSR has received the LDP-MAPPING from the downstream LSR and the LSP is up and operational. -- RELEASE_AWAITED This state means that the LSR is waiting for the LDP-RELEASE in respond to the LDP-WITHDRAW sent by this LSR. -- RESOURCES_AWAITED This state means that the LSR is waiting for the label resources. -4.2 Events of the Upstream_LSP_Control_Block's State Machine +4.2 Events of the Upstream LSP Control Block's State Machine for Downstream Mode -- Internal Downstream Mapping - This event is sent by one Downstream_LSP_Control_Block's state + This event is sent by one Downstream LSP Control Block's state machine. The event is the result of receiving an LDP-MAPPING by the - Downstream_LSP_Control_Block's state machine. Or when the LDP peer is + Downstream LSP Control Block's state machine. Or when the LDP peer is discovered and there is a downstream Label available for this FEC. -- LDP Release The LSR receives an LDP-RELEASE from an upstream LSR. -- Internal Withdraw - This event is sent by Downstream_LSP_Control_Block's state machine. + This event is sent by Downstream LSP Control Block's state machine. The event is the result of receiving an LDP-WITHDRAW by the - Downstream_LSP_Control_Block's state machine. + Downstream LSP Control Block's state machine. -- Resource Available This event means the local resource (such as label) becomes available. -- Delete FEC This event means that either the FEC is removed from the forwarding table. -- Upstream Lost This event means that the upstream LDP peer is lost. -4.3 State Transitions of Upstream_LSP_Control_Block's State +4.3 State Transitions of Upstream LSP Control Block's State Machine for Downstream Mode | |(created when |a label is to be distributed | to the LDP peer) v +-------------------+ | | | IDLE |<--------------+ @@ -2838,37 +2841,36 @@ | | | | | +-------------------+ | | | | (Internal Downstream Withdraw) |(LDP Release) | +-------------------+ | | | | | +---->| RELEASE_AWAITED |---------------+ | | +-------------------+ -4.4 Upstream_LSP_Control_Block's State Machine for +4.4 Upstream LSP Control Block's State Machine for Downstream Mode 4.4.1 : State -- "IDLE" State: IDLE Event: Internal Downstream mapping - New State: Depends on the action. + New State: Depends on the action routine. Actions Choose an upstream label, connect the upstream label with the - downstream label. And go to state `ESTABLISHED' - - Propagate the LDP-MAPPING upstream. + downstream label, propagate the LDP-MAPPING upstream and go to state + `ESTABLISHED' If there is no resource for the upstream label, go to state `RESOURCE_AWAITED'. State: IDLE Event: LDP Release New State: IDLE @@ -2984,22 +2984,22 @@ Actions Release the upstream label and delete the control block. 4.4.2 : State -- "RELEASE_AWAITED" State: RELEASE_AWAITED Event: Internal Downstream Mapping - New State: RELEASE_AWAITED + New State: RELEASE_AWAITED Actions Ignore the message. State: RELEASE_AWAITED Event: LDP Release New State: IDLE @@ -3031,22 +3031,22 @@ Event: Delete FEC New State: RELEASE_AWAITED Actions Do nothing. State: RELEASE_AWAITED - Event: Upstream Lost + Event: Upstream Lost New State: IDLE Actions Release the upstream label and delete the control block. 4.4.2 : State -- "RESOURCE_AWAITED" State: RESOURCE_AWAITED @@ -3101,33 +3102,33 @@ State: RESOURCE_AWAITED Event: Upstream Lost New State: IDLE Actions Delete the control block. -4.5 State of the Downstream_LSP_Control_Block's State Machine +4.5 State of the Downstream LSP Control Block's State Machine for Downstream Mode -- IDLE This is the initial LSP state. -- ESTABLISHED This state means that the LSR has received the LDP-MAPPING from the downstream LSR. -3.2.4.6 Events of the Downstream_LSP_Control_Block's State Machine +3.2.4.6 Events of the Downstream LSP Control Block's State Machine for Downstream Mode -- LDP Mapping The LSR receives an LDP-MAPPING from a downstream LSR. -- LDP Withdraw The LSR receives an LDP-WITHDRAW from a downstream LSR. @@ -3136,26 +3136,25 @@ The FEC is deleted from the forwarding table. -- Next Hop Change The next hop for this FEC is change to different LSR. -- Downstream Lost The downstream peer is gone. -4.7 State Transitions of Downstream_LSP_Control_Block's State +4.7 State Transitions of Downstream LSP Control Block's State Machine for Downstream Mode | - |(FEC is being added into the forwarding - table) + |(FEC is being added into the forwarding table) v +-------------------+ | | | IDLE |<--------------+ | | | +-------------------+ | | | | |(LDP Withdraw) | |(Internal New NH) | |(Downstream Lost) @@ -3164,36 +3163,36 @@ v | +-------------------+ | | | | | ESTABLISHED |---------------+ | | +-------------------+ | |(FEC is deleted from the forwarding table) v -4.8 Downstream_LSP_Control_Block's State Machine +4.8 Downstream LSP Control Block's State Machine for Downstream Mode 4.8.1 : State -- "IDLE" State: IDLE Event: LDP mapping New State: ESTABLISHED Actions For all the LDP peers except the downstream LSR which assigned the - label, create an Upstream_LSP_Control_Block, and pass the event - `Internal Downstream Mapping' to each of the - Upstream_LSP_Control_Block's state machines. + label, create an Upstream LSP Control Block, and pass the event + `Internal Downstream Mapping' to each of the Upstream LSP Control + Block's state machines. State: IDLE Event: LDP withdraw New State: IDLE Actions Ignore the event. It is an internal implementation error. @@ -3291,78 +3290,78 @@ - If an LSR receives an LDP-REQUEST: If there is a next hop for this FEC and there is a Downstream_Control_Block for this FEC whose state is `ESTABLISHED', create a new Upstream_Control_Block and pass `internal Mapping' event to its state machine. - If an LSR receives an LDP-MAPPING: - Locate a Downstream_LSP_Control_Block which has the same FEC, the + Locate a Downstream LSP Control Block which has the same FEC, the same Downstream LDP Session Identifier and the same Downstream Label. - If a Downstream_LSP_Control_Block is found, pass the event `LDP + If a Downstream LSP Control Block is found, pass the event `LDP Mapping' to its state table. This could mean that the attributes of label binding have changed. - Otherwise, if there is no matching Downstream_LSP_Control_Block - found, find a Downstream_LSP_Control_Block of this FEC and its next + Otherwise, if there is no matching Downstream LSP Control Block + found, find a Downstream LSP Control Block of this FEC and its next hop is the this downstream peer, pass the event `LDP Mapping' to its state machine. - If an LSR receives an LDP-RELEASE: - Locate an Upstream_LSP_Control_Block which has the same FEC, the same + Locate an Upstream LSP Control Block which has the same FEC, the same Upstream Label, the same Upstream LDP Session Identifier. If no - Upstream_LSP_Control_Block is found, ignore the message. If an - Upstream_LSP_Control_Block is found, send the event `LDP Release' to + Upstream LSP Control Block is found, ignore the message. If an + Upstream LSP Control Block is found, send the event `LDP Release' to its state machine. - If an LSR receives an LDP-WITHDRAW: - Find a Downstream_LSP_Control_Block which has the same FEC, the same - Downstream LDP Session Identifier and the same Downstream Label. Pass - the event `LDP Withdraw' to its state machines. + Find a Downstream LSP Control Block which has the same FEC, the same + Downstream LDP Session Identifier and the same Downstream Label. + Pass the event `LDP Withdraw' to its state machines. - If an Upstream LDP peer is lost: Pass the event `Upstream Lost' to the state machines of all the - Upstream_LSP_Control_Blocks whose upstream LDP peer is that LSR. + Upstream LSP Control Blocks whose upstream LDP peer is that LSR. - If a Downstream LDP peer is lost: Pass the event `Label Withdraw' to the state machines of all the - Downstream_LSP_Control_Blocks whose the downstream LDP peer is that + Downstream LSP Control Blocks whose the downstream LDP peer is that LSR. - If a next hop of an FEC is changed: - Find all the Downstream_LSP_Control_Blocks which has the same FEC and + Find all the Downstream LSP Control Blocks which has the same FEC and the same next hop and pass the event `Next Hop Change' to their state machine - If there is a FEC being added to the forwarding table - Create a new Downstream_LSP_Control_Block with state `IDLE' + Create a new Downstream LSP Control Block with state `IDLE' - If the FEC is deleted from the forwarding table Send the `Delete FEC' event to the its control block. - If an LSR receives an LDP-NAK from an upstream LSR: Ignore the message. An LDP-NAK should never appear in the downstream-mode LSR - If an LSR receives an LDP-NAK from a downstream LSR: - Ignore the message. It is an protocol error from the downstream LSR. + Ignore the message. It is a protocol error from the downstream LSR. 5. Security Considerations This document is provided as an informational extension of the LDP specification [4]. State machines presented here are intended to clarify procedures defined in the LDP specification, but do not supplant or override definitions and procedures provided there. Implementations of a state machine may be vulnerable to spurious events generated by an external source. In this document, events fall @@ -3372,21 +3371,22 @@ LDP messages may be protected using mechanisms described in the LDP specification. See "Security Considerations" in the LDP specification [4]. Security considerations relating to generation of spurious internal events are not addressed in this document. 6. Acknowledgements The authors would like to acknowledge the helpful comments and - suggestions of the following people: Bob Thomas and Myunghee Son. + suggestions of the following people: Bob Thomas, Myunghee Son and + Adrian Farrel. 7. Authors' Address Christophe Boscher Alcatel Le Mail 44700 Orvault France Phone: (33) 251781828 @@ -3408,34 +3408,34 @@ Durham, NH 03824 Phone: (603) 659-3386 Email: ewgray@lucent.com Liwen Wu Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA 01824 U.S.A - Phone: 978-224-3087 + Phone: 978-244-3087 Email:liwwu@cisco.com 8. References 1."MPLS Using LDP and ATM Switching", Bruce Davie, Jeremy Lawrence, Keith McCloghrie, Yakov Rekhter, Eric Rosen, George Swallow, Paul Doolan, work in progress, Internet Draft, 2."Multiprotocol Label Switching Architecture", Eric C Rosen, Arun Viswanathan, Ross Callon, work in progress, Internet Draft, 3."Definition of Managed Objects for the Multiprotocol Label Switching, Label Distribution Protocol (LDP)", Joan Cucchiara, Hans Sjostrand, James V. Luciani, work in progress, Internet Draft, + ldp-mib-03.txt> 4. "LDP Specification", Loa Andersson, Paul Doolan, Nancy Feldman, Andre Fredette, Bob Thomas, work in progress, Internet Draft, 5. "Constraint-Based LSP Set up Using LDP", Bilel Jamoussi, et al., work in progress, Internet Draft,