CCAMP Working Group D. Caviglia
Internet-Draft D. Bramanti
Expires: January 16, 2009 Ericsson
D. Li
Huawei Technologies Co., LTD.
S. Bardalai
Fujitsu Network Communications Inc
July 15, 2008
RSVP-TE Signaling Extension For The Conversion Between Permanent
Connections And Soft Permanent Connections In A GMPLS Enabled Transport
Network.
draft-ietf-ccamp-pc-spc-rsvpte-ext-01.txt
Status of this Memo
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Abstract
We would like to dedicate this work to our friend and colleague Dino
Bramanti, who passed away at the early age of 38. Dino has been
involved in this work since its beginning.
In a transport network scenario, where Data Plane connections
controlled either by GMPLS Control Plane (Soft Permanent Connections
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- SPC) or by Management System (Permanent Connections - PC) may
independently coexist, the ability of transforming an existing PC
into a SPC and vice versa - without actually affecting Data Plane
traffic being carried over it - is a requirement. See draft
"draft-ietf-ccamp-pc-and-reqs-04.txt [1]. This memo provides a minor
extension to RSVP-TE [RFC2205],[RFC3471],[RFC3473],[RFC4872]
signaling protocol, within GMPLS architecture, to enable such
connection ownership transfer and describes the proposed procedures.
Failure conductions and subsequent roll back are also illustrated
taking into account that an handover failure must not impact the
already established data plane connections.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Overview Of Proposed RSVP-TE Based Solution . . . . . . . . . 3
5. MP to CP handover: LSP Ownership Transfer From Management
Plane To Control Plane . . . . . . . . . . . . . . . . . . . . 5
5.1. MP to CP Handover Procedure Success . . . . . . . . . . . 6
5.2. MP to CP Handover Procedure Failure Handling . . . . . . . 7
5.2.1. MP to CP Handover Failure - Path Failure . . . . . . . 7
5.2.2. MP to CP Handover Failure - Resv Error . . . . . . . . 8
6. CP to MP handover : LSP Ownership Transfer From Control
Plane To Management Plane . . . . . . . . . . . . . . . . . . 13
6.1. CP to MP Handover Procedure Success . . . . . . . . . . . 13
6.2. CP to MP Handover Procedure Failure . . . . . . . . . . . 14
7. Discovery Phase . . . . . . . . . . . . . . . . . . . . . . . 14
8. Alternative Way Of Retrieving Information Needed For MP To
CP Handover . . . . . . . . . . . . . . . . . . . . . . . . . 15
9. RSVP Message Formats . . . . . . . . . . . . . . . . . . . . . 16
10. Objects Modification . . . . . . . . . . . . . . . . . . . . . 17
10.1. Administrative Status Object . . . . . . . . . . . . . . . 17
10.2. Error Spec Object . . . . . . . . . . . . . . . . . . . . 18
11. Acknoledgments . . . . . . . . . . . . . . . . . . . . . . . . 19
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19
13. Security Considerations . . . . . . . . . . . . . . . . . . . 20
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
15.1. Normative References . . . . . . . . . . . . . . . . . . . 20
15.2. Informa</artwork>tional References . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Intellectual Property and Copyright Statements . . . . . . . . . . 23
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1. Introduction
In a typical traditional transport network scenario, Data Plane
connections between two endpoints are controlled by means of a
Network Management System (NMS) operating within Management Plane
(MP). NMS/MP is the owner of such transport connections, being
responsible of their set up, tear down and maintenance.
The adoption of a GMPLS Control Plane over networks that are already
in service - controlled by NMS at Management Plane level - introduces
the need for a procedure able to coordinate a control handover of a
generic data plane connection from MP to CP.
In addition, the control handover in the opposite direction, from CP
to MP should be possible as well. The procedures described in this
memo can be applied to any kind of LSP and network architecture.
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 [RFC2119].
3. Motivation
The main motivation behind this work is the definition of a simple
and very low impacting procedure that satisfies the requirements
defined in "draft-ietf-ccamp-pc-and-reqs-04.txt [1]. Such procedure
is aimed at giving the transport network operators the chance to
convert existing LSP provisioned as PC by NMS to SPC without
disrupting user traffic flowing on it. Conversion from PC to SPC
(i.e. when existing Data Plane connection ownership and control is
passed from MP to CP) has been proposed as mandatory requirement,
while the opposite operation, SPC to SC conversion, has been
considered as a nice-to-have feature that can be seen as a back-out
option. For more details on requirements and motivations please
refer to "draft-ietf-ccamp-pc-and-reqs-04.txt [1].
4. Overview Of Proposed RSVP-TE Based Solution
The whole process comprises of the discovery and conversion phases.
The discovery phase being described in this document is an OPTIONAL
procedure and not mandatory for the conversion phase to proceed. The
discovery phase is typically initiated by the operator and is
performed hop-by-hop in order to discover the route. The route
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discovered SHOULD be consistent with the network topology. For
example, for a multi-layer network the hops discovered should be
contained within the same layer.
Prior to initiating the discovery process it is assumed that the
Control Plane domains have been established. The operator at the
originating node can optionally specify the terminating end-point at
the time of initiating the discovery request or it could be
automatically discovered. For example, at a network layer boundary
the discovery process can be terminated generating a response back to
the originator. Another possibility is to terminate the request at
the Control Plane domain boundary.
For conversion to PC or SPC the conversion phase will create an RSVP-
TE session along the discovered or user-specified route and bind with
the existing Management Plane owned cross-connect resources (e.g.
lambdas, time slots and reserved bandwidth)and at the same time
transfer the ownership to the Control Plane. For conversion to PC
the conversion phase will delete the existing RSVP- TE session
information without deleting the cross-connect resources and transfer
the ownership to the Management Plane.
Proposed procedure relies on the utilization of a newly introduced
flag, here named Handover flag, in the Administrative Status Object
[RFC3471] and [RFC3473]. The point is that standard RSVP-TE
signaling flow can be used to inform nodes about the ownership
handover request regarding one LSP that is already in place on their
Data Plane, where such flow has to be flagged in order to
discriminate it from normal, Data Plane affecting, LSP setup/release
procedure. When a LSP owned by Management Plane (i.e. a PC) has to
be handed over to Control Plane (i.e. converted into a SPC), a
signaling set-up with HANDOVER flag set has to be sent from ingress
node.
For the opposite procedure (when a LSP owned and controlled by
Control Plane has to be handed over to Management Plane, i.e. SPC to
PC conversion - or back out procedure for previous case) a signaling
tear-down with HANDOVER flag set has to be sent from ingress or
egress node, following the same procedure of a normal tear-down, from
which is recognizable again by reading flag value.
So, basically the HANDOVER flag is introduced and exploited to tell
apart a normal set-up (or tear-down) procedure - that has to trigger
an action on Data Plane state at each addressed node along the path
as usual - from the LSP ownership handover procedure that MUST leave
untouched Data Plane state.
This is in some way similar as an approach to the Restart Procedure,
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( [RFC2119]), in the sense that the status of the physical resources
at Data Plane has to stay unmodified but the associated information
allowing its control has to be transferred. The modification
proposed in this document refers only to Administrative Status
object, that is, the message flow is left unmodified for both set-up
and deletion. Moreover a new Error Value is defined to identify the
failure of an Handover procedure.
It is worth stressing that, when the LSP over Data Plane is adopted
either by CP or MP, i.e. at the end of signaling with Handover flag
set, normal CP procedures or MP procedures have to take their place
as usual when needed. This means that a LSP formerly owned by MP,
signalled within CP with Handover flag set (i.e. handed over to CP)
can be controlled by usual relevant Control Plane signaling flows
(i.e. with Handover flag not set). The same applies when considering
the handover of a LSP from CP to MP when, at the end of procedure,
the LSP belongs to Management Plane and can be fully controlled by
NMS. In other words, after the LSP handover procedures have taken
place, the LSP is not different from the other LSP owned by handover
destination entity and it has to be treated with usual rules for that
entity.
Following paragraphs give detailed description of proposed "MP to CP
handover" and "CP to MP handover" procedure, based on Handover flag
usage. Handover of a bidirectional LSP is assumed. The case of
unidirectional LSP can be easily derived from that.
5. MP to CP handover: LSP Ownership Transfer From Management Plane To
Control Plane
Let's consider the case of a Data Plane connection created by NMS.
The Management Plane has the ownership and control of the LSP and
wants to hand it over to Control Plane. At the ingress node NMS
initiates the transfer of LSP related information residing within
Management Plane to RSVP-TE records within Control Plane. We assume
that this happens under operator or management application control
and in particular that:
- Control requests are sent to the ingress LSR by the MP
- The MP has some way of knowing when the CP has completed its
task or has failed.
Ingress node collects from MP all the LSP related information needed
at Control Plane level. The way this operation is done and where
such information is collected within MP is outside the scope of this
document. One possible (optional) way to collect it is explained in
Section 8.
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A relevant part of such information is represented by the LSP path,
which has to be handed over to CP to be used by signalling entity to
fill the Explicit Route Object (ERO) during setup. In order to
support the MP to CP handover of LSP, the ERO object in the Path
message MUST be filled with all the LSP relevant information down to
the Label level. That can be done by means of the object and
procedures defined in [RFC3473].
The precise filling of the ERO object is needed as we are assuming
that the LSP already exists in Data Plane and that every signalling
relevant info about it is available and accessible to MP in terms of
required LSP parameters to build a RSVP-TE PATH message. After the
collection of all the LSP related information, the ingress node
starts the handover procedure issuing a RSVP-TE PATH message
including the Administrative Status Object with both HANDOVER and
REFLECT flags set. The R flag set assures that also the Resv message
will set the H flag. Upon reception of such RSVP-TE PATH, a node
MUST be able to understand that a MP to CP handover procedure is in
progress by reading the Handover flag.
Either the ingress node of the LSP (upon request from MP) and
intermediate and egress nodes (when receiving a Path/Resv message
containing an Administrative Status object with the Handover flag
set) are informed about the fact that a LSP handover procedure is
requested or ongoing. The node assumes that a Data Plane resource
related to the info carried in Path Message is already allocated and
in place.
The following of the section illustrates in detail the procedure in
cases in success and failures.
5.1. MP to CP Handover Procedure Success
Upon receiving a Path Message, each node SHOULD check the consistence
of the actual Data Plane status of such resource. Say the check goes
OK (failure cases are illustrated in the next sections), then a
RSVP-TE record for the LSP is created associating it to the
corresponding Data Plane state. The node accepts all the LSP
information carried in the Path message (if the node is not the
Ingress LER of the LSP, otherwise the information is sent from
relevant MP entity) and stores it in Path State Block. After that,
the procedure goes on as described below.
After propagating handover Path message, a node MUST wait for a Resv
message including Administrative Status Object with Handover flag
set. After receiving it, the actual migration of LSP information is
complete, the LSP is left completely under control of RSVP- TE within
Control Plane. This means that any memory about the former MP
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ownership of the LSP is lost. If a Confirmation message was
requested, then it is generated. The handover procedure does not
modify the Confirmation procedure.
5.2. MP to CP Handover Procedure Failure Handling
In case of Management Plane to Control Plane Procedure, two different
failure scenarios can happen: Path Failure and Resv Failure.
Moreover, each failure can be due to two different causes: Data Plane
failure or Communication Failure. A section for each combination
will be analyzed in the following.
5.2.1. MP to CP Handover Failure - Path Failure
5.2.1.1. MP to CP Handover Failure - Path Message and Data Plane
Failure
The handover procedure can fail due to different causes, but in any
case the network status but be immediately rollbacked to the one
previous to the handover procedure. The failure can happen during
the Path message or the Resv message forwarding. In this paragraph
we will analyze the first case.
| Path | | |
|---------------------->| Path | |
| |----------------------X| |
| | | |
| Path Err | | |
|<----------------------| | |
| | | |
Ingress LER LSR A LSR B Egress LER
If an error occurs in an LSR or a LER, the last node that has
received the Path message MUST send a Path Error message in the
upstream direction including an Error_Spec object and the Handover
flag set. The upstream nodes MAY process the Error_Spec object.
5.2.1.2. MP to CP Handover Failure - Path Message and Communication
failure
Other possible scenarios are shown in the following pictures and
consist on the unreachability of a node of the LSP.
The below scenario postulates the usage of a reliable message
delivery based on the mechanism defined in [RFC2961]
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| Path | | |
|---------------------->| Path | |
| |------------X | |
| |------------X | |
| | ... | |
| |------------X | |
| | | |
| Path Err | | |
|<----------------------| | |
| | | |
Ingress LER LSR A LSR B Egress LER
The Path message sent from LSR A towards LSR B is lost or does not
reach the destination for any reason. A reliable delivery mechanism
is implemented, LSR A retransmits the Path Message for a configurable
number of times, then, if no ack is received, a Path Error message is
sent back to the ingress LER and the adoption procedure aborted.
In the next scenario RSVP-TE messages are sent without reliable
message delivery, that is, no [RFC2961] MessageID procedure is used.
| Path | | |
|---------------------->| Path | |
| |------------X | |
| | | |
| | | |
|----TIMER EXPIRES------| | |
| Path Tear | | |
|---------------------->| | |
| | | |
Ingress LER LSR A LSR B Egress LER
If the Resv Message is not received by the expiration of a timer set
by the ingress LER, the adoption procedure is again aborted and a
PathTear message MAY be sent in the downstream direction with the H
bit set
5.2.2. MP to CP Handover Failure - Resv Error
5.2.2.1. MP to CP Handover Failure - Resv Error and Data Plane failure
In case a failure occurs during the Resv Message forwarding, things
are quite different, because after the handover procedure an LSR is
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not able to distinguish an LSP created by the Control Plane from an
LSP created by the Management Plane and then moved to the Control
Plane.
| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| |X----------------------| |
| Path Err | Resv Err | |
|<----------------------|---------------------->| Resv Err |
| | |---------------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
In the case shown in the above picture, the failure occurs in LSR A.
A Resv Error message is sent in the downstream direction and a Path
Error message is sent in the upstream direction.
Please note that the failure occurred after the handover procedure
was successfully completed in LSR B. This means that LSR B is no
longer able to know if the LSP was created by the Control Plane or a
handover procedure took place.
Upon receiving a Resv Error message, LSR B would delete the LSP also
from the Data Plane point of view. To prevent this from happening,
LSR A MUST include an Error_Spec object into the Resv Error message
setting the handover flag. The downstream nodes MUST process the
Error Spec object, move the LSP ownership back to the Management
Plane and MUST NOT modify the Data Plane.
5.2.2.2. MP to CP Handover Failure - Resv Error and Communication
failure
In case a Resv Message cannot reach one or more of the downstream
nodes, the procedure is quite similar to the one previously seen
about the Path Message. Even in this case it is possible to
distinguish two different scenarios.
In the first scenario we consider the utilization of a reliable
message delivery based on the mechanism defined in [RFC2961]. After
a correct forwarding of the Path message along the nodes of the LSP,
the Egress LSR sends a Resv message in the opposite direction. It
might happen that the Resv message does not reach an LSR, say LSR A.
LSR B, after sending the Resv message again for a configurable number
of times, sends a Resv Error message in the downstream direction
towards the Egress LER and a Path Error message in the upstream
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direction towards the Ingress LER in order to inform the nodes of the
path that the adoption procedure has failed and that the LSP
ownership is to be moved back to the management plane.
| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| | X-----------| |
| | X-----------| |
| | ... | |
| | X-----------| |
| | | |
| Path Err | Path Err | Resv Err |
|<----------------------|<----------------------|---------------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Please note that the failure occurred after the handover procedure
was successfully completed in the Egress LER. This means that it is
no longer able to know if the LSP was created by the Control Plane or
a handover procedure took place.
Upon receiving a Resv Error message, the downstream nodes would
delete the LSP also from the Data Plane point of view. To prevent
this from happening, LSR B MUST include an Error_Spec object into the
Resv Error message setting the Handover flag. The downstream nodes
MUST process the Error Spec object, move the LSP ownership back to
the Management Plane and MUST NOT modify the Data Plane.
Considering that the Resv message did not manage to reach LSR A, it
is highly probable that the Path Error would fail too. Due to this
fact, a configurable timer MUST be set on the Ingress LER after
sending the path and on LSR A after forwanding it. When the timer
expires, if no Resv or Path Error message is received, the handover
procedure MUST be aborted and the LSP ownership returned to the
Management Plane.
The following picture, on the other hand, shows the scenario in which
no reliable delivery mechanism is implemented.
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| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| | X-----------| |
| | | |
| | | |
|----TIMER EXPIRES------| | |
| Path Tear | Path Tear | Path Tear |
|---------------------->|---------------------->|---------------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
After sending the path message, the ingress LER sets a timer. If non
Resv message is received before the timer expires, then the adoption
procedure is aborted and the Ingress LER MAY signal it by a Path Tear
message with the H bit set.
5.2.2.3. MP to CP Handover Failure - Node Graceful Restart
In case one of the nodes restarts and graceful restart is enabled
then one of the following scenarios will happen.
Case I
Restart timer is not infinite. In the sequence diagram below, assume
LSR A restarts. In case the ingress LER does not receive the Resv
message in time it will abort the conversion process by generating a
PathTear message downstream. Also, if LSR A does not complete the
restart process within the restart time interval then LSR B will
start tearing down all LSPs between LSR A and LSR B and this includes
the LSP that is being used to carry out the conversion of MP
resources to CP. LSP B will generate a PathTear message downstream
and a PathErr message upstream. Both LSR B and the egress LER will
not release the data-plane resources because in both nodes the H-bit
is set in the PSB.
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| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| X X-----------| |
| PathTear | |
|----------X | |
| Restart Timer |
| PathErr Expires PathTear |
| X-----------|---------------------->|
| X | |
| | | |
Ingress LER LSR A LSR B Egress LER
Case II
Restart timer is infinite. The sequence is quite similar to the
previous one. In this sequence the restart timer will not expire in
LSR B since it is run infinitely. Instead after LSR A restarts LSR B
will start the recovery timer. The recovery timer will expire since
there will be no Path message with the RECOVERY LABEL received from
LSR A given the ingress node had already removed the PSB after it
aborts the conversion process. Thus LSR B will tear-down the
specific LSP that is being used to convert the MP resources to CP by
generating a PathTear downstream and PathErr upstream. Similarily to
the previous case both LSR B and the egress LER will not release the
data-plane resources because the H-bit is set in the PSB.
| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| X X-----------| |
| PathTear | |
|----------X | |
| | |
| X | |
| | | |
| | Recovery Timer |
| | PathErr Expires PathTear |
| | X-----------|---------------------->|
| | |
Ingress LER LSR A LSR B Egress LER
Case III
Ingress LER did not abort the conversion process. Once LSR A
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restarts the ingress LER will re-generate the Path message with the
H-bit set. When LSR B receives the Path message it may generate a
PathErr since the RECOVERY LABEL may not be present. The reason is
LSR A may not have the label. Similarily LSR B and egress LER will
not release the data-plane resources since the H-bit is set.
| Path | Path | Path |
|---------------------->|---------------------->|---------------------->|
| | | Resv |
| | Resv |<----------------------|
| X X-----------| |
| | |
| | |
| X | |
| Path | Path | |
|---------------------->|---------------------->| |
| PathErr | PathErr | PathTear |
|<----------------------|<----------------------|---------------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
6. CP to MP handover : LSP Ownership Transfer From Control Plane To
Management Plane
Let's now consider the case of LSP Ownership Transfer From Control
Plane To Management Plane. Also in this sections we will analyze the
handover procedure success and failure.
6.1. CP to MP Handover Procedure Success
The scenario is still a Data Plane connection between two nodes
acting as ingress and egress for a LSP. But let's assume in this
case that Control Plane has the ownership and control of the LSP and
that we want to hand it over to Management Plane. This means that at
the end of such procedure, the Data Plane state related to that
connection is still untouched, but the LSP related information record
is no more owned by RSVP-TE over Control Plane.
In other words, after LSP ownership transfer from CP to MP, the LSP
is no more under control of RSVP-TE, which is no more able to "see"
the LSP itself. This Section covers the procedure needed to manage
this procedure as a dual, opposite procedure respect to the one
described in previous section. The procedure is performed at a
signaling level as described in Section 7.2.1 of [RFC3473].
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At LSP ingress node, relevant MP entity requests the ownership of the
LSP, How this is done is outside the scope of memo. Ingress node and
MP exchange the relevant information for this task and then
propagates it over Control Plane by means of RSVP-TE tear down
signaling flow as detailed below.
Ingress node MUST send out a Path message, with Handover and Reflect
bits in Admin Status set. No action is taken over Data Plane and
Control Plane keeps track of special handover state the LSP is in.
Transit and Egress nodes, upon reception of such handover Path,
propagate it without any Data Plane action, retaining the handover
state information associated to the LSP. After that, every node
waits until the Handover bit is received back in the Resv. Then a
PathTear is issued and the whole LSP information record is cleared
from RSVP- TE data structures. In other words, a normal LSP tear
down signaling is exchanged between nodes traversed by the LSP, but
handover flag set in Path message indicates that no Data Plane action
has to correspond to Control Plane signaling. At the end of handover
tear down signaling flow, the LSP is released from Control Plane
point of view, but its Data Plane state is still unmodified and it is
now owned and controllable by MP.
6.2. CP to MP Handover Procedure Failure
Failures during CP to MP handover procedure MUST be managed at
signaling level as in normal LSP tear down procedure. The only
difference is the handover flag set in Administrative Status Object
inside Path message which MUST be read by receiving node and imposes
that no action has to be made over Data Plane resource whose
corresponding Control Plane record is involved in handover procedure.
7. Discovery Phase
The discovery process starts at the orignating end-point, which
transmits a discovery request Notify message on the link identified
to be part of the LSP to be converted. The Notify message is
forwarded hop-by-hop tracing the LSP information and identifying the
next-hop. The assumption being made here is that information
regarding individual neighbors is already available.
In case the destination address is not known the RSVP-TE session
destination address MAY not be specified (i.e. set to 0.0.0.0) in the
discovery request Notify message.
Any node that decides to terminate the discovery process will not
forward the Notify message and will generate a discovery response
Notify message.
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If any error prevents the discovery process to be successfully
completed, the ERROS_SPEC object in the response Notify message will
be filled with a failure code, else it MUST be se set to the success
code. The discovery response message SHOULD be sent hop-by-hop back
to the requestor.
In case the destination address in the request message is 0.0.0.0
then it MUST be filled in by the terminating entity in the response
message SESSION object.
The format of the Notify Message is as follows:
<Notify message> ::= <Common Header> [ <INTEGRITY> ]
[[ <MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>]...]
[ <MESSAGE_ID> ]
<ERROR_SPEC>
<discovery info>
<discovery info> ::= <SESSION> <RSVP_HOP> <RECOVERY_LABEL>
[ <ADMIN_STATUS> ]
[ <POLICY DATA> ]
[ <SESSION_ATTRIBUTES>]
[ <UPSTREAM_LABEL> ]
[ <RECORD_ROUTE> ]
The RECORD_ROUTE object in the discovery response SHOULD be put
together such that it can be directly used in a Path message for the
coversion phase. For example, explitcit label sub-objects can be
specified only for outgoing links in the Path message [RFC3473].
8. Alternative Way Of Retrieving Information Needed For MP To CP
Handover
An alternative way of getting the LSP related information required
for the MP to CP handover is also proposed in this draft. The
rationale behind this way is that only a minimal set of information
is handed over from MP to CP at LSPs Ingress node. Instead of
collecting within MP all the LSP relevant information down to the
Label level, formatting it to an ERO and passing it to CP, as in
previously described solution, it is possible to start with a minimum
amount of information. At the ingress node, the information needed
to specify the LSP is the outgoing interface ID, upstream label and
downstream label of this interface and the incoming interface ID of
egress node. The remaining information about an existing LSP can
then be collected hop by hop, as the signalling is going on, by
looking up the cross-connection table in Data Plane at each node
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along the LSP path.
Starting from the information available at ingress LER about the
outgoing interface ID of that ingress node, the incoming interface ID
of next hop can be found by looking up the link resource table/
database in the LER itself. Following the similarity existing
between the MP to CP handover procedure and the Restart Procedure,
the Recovery Label Object MUST be used to carry the downstream label
and the Upstream Label Object MUST be used to carry the upstream
label to the next node.
The Path message is hence built with the Recovery Label Object
([RFC3473]) and the Upstream Label Object ([RFC3473]), where the
upstream label and downstream label of ingress outgoing interface of
the LSP are included in these two objects. In addition to above
mentioned objects, the Path message MUST include the Administrative
Status Object with HANDOVER flag set, as already defined in previous
chapter for the detailed ERO based way of proceeding. Such handover
Path is sent to the incoming interface of next hop. When this Path
message reaches the second node along the LSP path, the information
about incoming interface ID and the upstream and downstream labels of
this interface is extracted from it and it is used to find next hop
outgoing interface ID and the upstream/downstream labels by looking
up the Data Plane cross-connection table.
After having determined in this way the parameters describing the
LSPs next hop, the outgoing Path message to be sent is built
replacing the Recovery Label Object and Upstream Label Object content
with the looked-up values of upstream and downstream labels.
Re-iterating this procedure for each transit node along the LSP path,
it is possible to make the handover Path message reach the egress
node, exactly following the LSP that is in place over Data Plane.
The ERO MAY in this case be included in the Path message as an
optional object, and MAY be filled with the LSP relevant information
down to either the port level with interface ID or the Label level
with upstream and downstream labels. The ERO can be used to check
the consistence of resource in Data Plane down to the port level or
label level at each intermediate node along the LSP path.
9. RSVP Message Formats
This memo does not introduce any modification in RSVP messages object
composition.
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10. Objects Modification
The modifications required concern two RSVP Objects: the
Administrative Status and the Error Spec Object.
10.1. Administrative Status Object
This memo introduces a new flag into the Administrative Status
object. The Admin_Status Object is defined in [RFC3473]. This
document uses the H-bit of the Admin_Status object. The bit is bit
number (TBD by IANA). The format of the Admin_Status Object is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(196)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R| Reserved |H|L|I|C|T|A|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The different flags are defined as follows:
- Reflect (R): 1 bit - Defined in [RFC3471]
When set, indicates that the edge node SHOULD reflect the object/
TLV back in the appropriate message.
- Handover (H): 1bit
When set, the H bit indicates that a Handover procedure for the
transfer of LSP ownership between Management and Control Planes is
ongoing.
- Lockout (L): 1 bit - Defined in [RFC4872]
When set, forces the recovery LSP to be temporarily unavailable to
transport traffic (either normal or extra traffic).
- Inhibit Alarm Communication (I): 1 bit - Defined in [RFC4783]
When set, indicates that alarm communication is disabled for the
LSP and that nodes SHOULD NOT add local alarm information.
- Call Control (C): 1 bit - Defined in
draft-ietf-ccamp-gmpls-rsvp-te-call-04 [2]
This bit is set when the message is being used to control and
manage a Call.
-Testing (T): 1 bit - Defined in [RFC3471]
When set, indicates that the local actions related to the
"testing" mode should be taken.
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- Administratively down (A): 1 bit - Defined in [RFC3471]
When set, indicates that the local actions related to the
"administratively down" state should be taken.
- Deletion in progress (D): 1 bit - Defined in [RFC3471]
When set, indicates that that the local actions related to LSP
teardown should be taken.
The H bit must be used in conjunction with the R flag when is set in
the Path message. This will assures that the Resv message will
maintain the H flag set.
10.2. Error Spec Object
It is possible that a failure, such as the lost of DCN connection or
the restart of a node, occurs during the LSP ownership handing over.
In this case the LSP adoption MUST be interrupted and the ownership
of the LSP MUST be moved back to the Plane it belonged to. It is
important that the transaction failure MUST not affect the Data
Plane. The LSP MUST be kept in place and no traffic hint MUST occur.
The failure is signaled by Path and Resv Error Messages, which
include an Error_Spec_Object specifying the causes of the failure.
This memo introduces a new Flag and a new Error Code(with different
Error Values) into the Error_Spec Object, defined in [RFC2205].
* ERROR_SPEC class = 6.
* IPv4 ERROR_SPEC object: Class = 6, C-Type = 1
+-------------+-------------+-------------+-------------+
| IPv4 Error Node Address (4 bytes) |
+-------------+-------------+-------------+-------------+
| Flags | Error Code | Error Value |
+-------------+-------------+-------------+-------------+
The fields of the object are defined as follows:
- Error Node Address
The IP address of the node in which the error was detected.
- Error Code
A one-octet error description.
- Error Value
A two-octet field containing additional information about the
error. Its contents depend upon the Error Type
- Flags
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Flags assigned values:
* 0x01 = InPlace
* 0x02 = NotGuilty
Proposed new value (TBD) = HandOverFailure
The new flag is "Handover Procedure Failure" and the actual value is
(TBD by IANA). When this flag is set during an handover from
Management Plane to Control Plane, the receiver must delete the
Control Plane status associated with the LSP and move the ownership
of the cross-connections back to the Management Plane. The proposed
Error Code is "Handover Procedure Failure", and its value is (TBD by
IANA)(33). For this Error Code the following Error Values are
defined: 1 = Cross-connection mismatch 2 = DCN error
11. Acknoledgments
We wish to thank Adrian Farrel for his editorial assistance and
precious advices to prepare this draft for publication. We also wish
to thank Nicola Ciulli, that contributed to initial stage of this
draft.
12. Contributors
Shan Zhu
Fujitsu Network Communications Inc.
2801 Telecom Parkway,
Richardson, Texas 75082
USA
Email: Shan.Zhu@us.fujitsu.com
Tel: +1-972-479-2041
Igor Bryskin
ADVA Optical Networking Inc
7926 Jones Branch Drive
Suite 615
McLean, VA - 22102
Email: ibryskin@advaoptical.com
Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova-Sestri Ponente, Italy
Phone: +390106002515
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Email: daniele.ceccarelli@ericsson.com
13. Security Considerations
The procedures described in this document rely completely on RSVP-TE
messages and mechanism. The use of Handover Flag set in Admin Status
Object basically informs the receiving entity that no operations are
to be done over Data Plane as consequence of such special signaling
flow. Using specially flagged signaling messages we want to limit
the function of setup and tear down messages to Control Plane, making
them not effective over related Data Plane resource usage. So, no
additional or special issues are arisen by adopting this procedure,
that aren't already brought up by the use of the same messages,
without handover flag setting, for LSP control. For RSVP-TE Security
please refer to [RFC3473].
14. IANA Considerations
IANA has been asked to manage the bit allocations for the
Administrative Status object ([RFC3473]). This document requires the
allocation of the Handover bit: the H-bit. IANA is requested to
allocate a bit for this purpose.
15. References
15.1. Normative References
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, April 2001.
15.2. Informa</artwork>tional References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
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Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC4872] Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
Extensions in Support of End-to-End Generalized Multi-
Protocol Label Switching (GMPLS) Recovery", RFC 4872,
May 2007.
[RFC4783] Berger, L., "GMPLS - Communication of Alarm Information",
RFC 4783, December 2006.
URIs
[1] <http://tools.ietf.org/html/draft-ietf-ccamp-pc-and-sc-reqs-04>
[2] <http://tools.ietf.org/html/
draft-ietf-ccamp-gmpls-rsvp-te-call-04>
Authors' Addresses
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: diego.caviglia@ericsson.com
Dino Bramanti
Ericsson
Via Moruzzi 1 C/O Area Ricerca CNR
Pisa
Italy
Email: dino.bramanti@ericsson.com
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Dan Li
Huawei Technologies Co., LTD.
Shenzhen 518129
Huawei Base, Bantian, Longgang
Italy
Email: dan.li@huawei.com
Snigdho Bardalai
Fujitsu Network Communications Inc
2801 Telecom Parkway
Richrdson, Texas 75082
USA
Email: Snigdho.Bardalai@us.fujitsu.com
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