CCAMP Working Group D. Caviglia
Internet-Draft D. Ceccarelli
Intended status: Standards Track D. Bramanti
Expires: August 19, 2010 Ericsson
D. Li
Huawei Technologies
S. Bardalai
Fujitsu Network
February 15, 2010
RSVP-TE Signaling Extension For Management Plane To Control Plane LSP
Handover In A GMPLS Enabled Transport Network.
draft-ietf-ccamp-pc-spc-rsvpte-ext-07
Abstract
In a transport network scenario, where Data Plane connections are
controlled either by a Generalized Multi-Protocol Label Switching
(GMPLS) Control Plane (Soft Permanent Connections - SPC) or by a
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. The requirements for the
conversion between permanent connections and switched connections in
a GMPLS Network are defined in [RFC5493].
This memo describes an extension to GMPLS RSVP-TE signaling that
enables the transfer of connection ownership between the Management
and the Control Planes. Such a transfer is referred to as a
Handover. This document defines all Handover related procedures.
This includes the handling of failure conditions and subsequent
reversion to original state. A basic premise of the extension is
that the handover procedures must never impact an already established
Data plane connection.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
Caviglia, et al. Expires August 19, 2010 [Page 1]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 19, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Caviglia, et al. Expires August 19, 2010 [Page 2]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Dedication . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. MP to CP handover: LSP Ownership Transfer From
Management Plane To Control Plane . . . . . . . . . . . . 6
4.2. MP to CP Handover Procedure Failure Handling . . . . . . . 7
4.2.1. MP to CP Handover Failure - Path Failure . . . . . . . 7
4.2.1.1. MP to CP Handover Failure - Path message and
Data Plane Failure . . . . . . . . . . . . . . . . 7
4.2.1.2. MP to CP Handover Failure - Path message and
Communication failure . . . . . . . . . . . . . . 8
4.2.2. MP to CP Handover Failure - Resv Error . . . . . . . . 9
4.2.2.1. MP to CP Handover Failure - Resv Error and
Data Plane failure . . . . . . . . . . . . . . . . 9
4.2.2.2. MP to CP Handover Failure - Resv Error and
Communication failure . . . . . . . . . . . . . . 10
4.2.2.3. MP to CP Handover Failure - Node Graceful
Restart . . . . . . . . . . . . . . . . . . . . . 12
4.3. CP to MP handover : LSP Ownership Transfer From
Control Plane To Management Plane . . . . . . . . . . . . 14
4.4. CP to MP Handover Procedure Failure . . . . . . . . . . . 15
5. Minimum Information for MP to CP Handover . . . . . . . . . . 17
6. RSVP Message Formats . . . . . . . . . . . . . . . . . . . . . 18
7. Objects Modification . . . . . . . . . . . . . . . . . . . . . 18
7.1. Administrative Status Object . . . . . . . . . . . . . . . 18
7.2. Error Spec Object . . . . . . . . . . . . . . . . . . . . 18
8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 20
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13.1. Normative References . . . . . . . . . . . . . . . . . . . 21
13.2. Informational References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
Caviglia, et al. Expires August 19, 2010 [Page 3]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
1. Introduction
In a typical traditional transport network scenario, Data Plane (DP)
connections between two endpoints are controlled by means of a
Network Management System (NMS) operating within the 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 Generalized MPLS (GMPLS) [RFC3945] Control Plane
(CP) in a network that is already in service - controlled by NMS at
MP level - introduces the need for a procedure able to coordinate a
controlled handover of a 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 a Label Switched Path (LSP) in any DP
switching technology and any network architecture.
This memo describes an extension to GMPLS Resource reSerVation
Protocol - Traffic Engineering (RSVP-TE) [RFC3471], [RFC3473]
signaling that enables the handover of connection ownership between
the Management and the Control Planes. All handover related
procedures are defined below. This includes the handling of failure
conditions and subsequent reversion to original state. A basic
premise of the extension is that the handover procedures must never
impact the exchange of user data on LSPs that are already established
in the DP.
1.1. Dedication
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.
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 impact procedure that satisfies the requirements defined
in [RFC5493]. Such a procedure is aimed at giving the transport
network operators the chance to handover the ownership of existing
Caviglia, et al. Expires August 19, 2010 [Page 4]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
LSPs provisioned by NMS from the MP to the CP without disrupting user
traffic flowing on them. Handover from MP to CP (i.e. when existing
DP connection ownership and control is passed from MP to CP) has been
defined as a mandatory requirement, while the opposite operation, CP
to MP handover, has been considered as a nice-to-have feature that
can be seen as an emergency procedure to disable the CP and take the
manual control of the LSP. For more details on requirements and
motivations please refer to [RFC5493].
4. Procedures
The modification defined in this document refers only to the
ADMIN_STATUS Object, that is, the message flow is left unmodified for
both LSP set-up and deletion. Moreover a new Error Value is defined
to identify the failure of a Handover procedure.
The following paragraphs give detailed description of the "MP to CP
handover" and "CP to MP handover" procedures, based on the usage a
newly defined bit called H bit.
Just as when setting up an LSP using the CP [RFC3473], the Path
message may contain full information about the explicit route
including the links and labels traversed by the LSP. This
information is encoded in the Explicit Route Object (ERO), and must
be supplied by the MP using details recorded when the LSP was
provisioned, or collected by the MP by inspecting the nodes along the
path.
Alternatively, and also just as when setting up an LSP using the CP
[RFC3473] the ERO may include less information such that the details
of the next hop have to be determined by each node along the LSP as
it processes the Path message. This approach may be desirable when
the full information is not available to the MP or cannot be passed
to the head-end node when initiating the handover from MP to CP.
This section (Section 4) describes the general procedures and
protocol extensions for MP to CP handover, and uses the case of a
fully detailed ERO to describe the mechanism. Section 5 describes
how each node behaves in the case of a limited amount of information
in the ERO.
Note that when handover is being performed for a bidirectional LSP
and the ERO contains full information including labels, the ERO
SHOULD include both upstream and downstream labels. Per Section
5.1.1 of [RFC3473], the labels are indicated on an output basis; this
means that the labels are used by the upstream node to create the
LABEL_SET Object and, for bidirectional LSPs, the UPSTREAM_LABEL
Caviglia, et al. Expires August 19, 2010 [Page 5]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
Object used in the outgoing Path message.
4.1. MP to CP handover: LSP Ownership Transfer From Management Plane To
Control Plane
The MP to CP handover procedure MUST create an RSVP-TE session along
the path of the LSP to be moved from MP to CP, associating it to the
existing cross-connected resources owned by the MP (e.g. lambdas,
time slots or reserved bandwidth) and at the same time transferring
their ownership to the CP.
The operator instructs the ingress node to handover control of the
LSP from the MP to the CP. In this handover mode, it supplies the
exact path of the LSP including any resource reservation and label
information.
The ingress MUST check that no corresponding Path state exists and
that corresponding Data Plane state does exist. If there is an
error, this MUST be reported to the operator and further protocol
action MUST NOT be taken.
The ingress signals the LSP using a Path message with the H bit and R
bit set in the ADMIN_STATUS object. In this mode of handover, the
Path message also carries an ERO that includes Label subobjects
indicating the labels used by the LSP at each hop. The ingress MUST
start the Expiration timer (see Section 4.2.1.2 for expiration of
this timer). Such timer SHOULD be configurable per LSP and have a
default value of 30 seconds.
Each Label Switching Router (LSR) that receives a Path message with
the H bit set checks to see whether there is any matching Path state.
- If matching Path state is found with the H bit set, this is a
Path refresh and should be treated accordingly [RFC3473].
- If matching Path state is found with the H bit clear, this is an
error and MUST be treated according to the error case description
in Section 4.2.1.1
- If no Path state is found, the LSR goes on to check whether
there is any matching Data Plane state.
- If no matching Data Plane state is found (including only
partially matching Data Plane state), this is an error or a race
condition. It MUST be handled according to the description in
Section 4.2.1.1
- If matching Data Plane state is found, the LSR MUST save the
Path state (including the set H bit), and MUST forward the Path
message to the egress. The LSR MUST retain any MP state
associated with the LSP at this point.
Caviglia, et al. Expires August 19, 2010 [Page 6]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
An egress LSR MUST act as any other LSR, except that there is no
downstream node to which to forward the Path message. If all checks
are passed, the egress MUST respond with a Resv with the H bit set.
A transit LSR MUST process each Resv according to the normal rules of
[RFC3473].
When an ingress LSR receives a Resv message carrying the H bit set,
it checks the Expiration Timer.
- If the timer is not running, the Resv is treated as a refresh and
no special action is taken [RFC3473].
- If the timer is running, the ingress MUST cancel the timer and
SHOULD notify the operator that the first stage of handover is
complete. The ingress MUST send a Path message that is no different
from the previous message except that the H bit MUST be clear.
The Path message with the H bit clear will travel the length of the
LSP and will result in the return of a Resv with the H bit clear
according to normal processing [RFC3473]. As a result, the H bit
will be cleared in the stored Path state at each transit LSR and at
the egress LSR. Each LSR SHOULD release any associated MP state
associated with the LSP when it receives the Path message with H bit
clear, but MAY retain the information according to local policy for
use in future MP processing.
When the ingress receives a Resv with the H bit clear, the handover
is completed. The ingress SHOULD notify the operator that the
handover is correctly completed.
4.2. MP to CP Handover Procedure Failure Handling
In the case of MP to CP Handover, two different failure scenarios can
happen: Path Failure and Resv Failure. Moreover, each failure can be
due to two different causes: DP failure or Communication Failure. In
any case the LSP ownership MUST be immediately rolled back to the one
previous to the handover procedure. A section for each combination
will be analyzed in the following.
4.2.1. MP to CP Handover Failure - Path Failure
4.2.1.1. MP to CP Handover Failure - Path message and Data Plane
Failure
In this paragraph we will analyze the case where the handover
procedure fails during the Path message processing.
Caviglia, et al. Expires August 19, 2010 [Page 7]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
| Path | | |
|--------------->| Path | |
| |---------------X| |
| | PathErr | |
| PathErr |<---------------| |
|<---------------| | |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 1: MP2CP - Path Msg and DP Failure
If an error occurs, the node detecting the error MUST respond to the
received Path message with a PathErr message, and MUST abort the
handover procedure. The PathErr message SHOULD have the
Path_State_Removed flag set [RFC3473], but implementations MAY retain
their local state and wait for Path state timeout as per normal RSVP
processing.
Nodes receiving a PathErr message MUST follow standard PathErr
message processing and the associated DP resources MUST NOT be
impacted. If the local CP state indicates that a Handover is in
progress (based on the H bit in the Path message) the LSR MUST revert
the LSP ownership to the MP.
4.2.1.2. MP to CP Handover Failure - Path message and Communication
failure
Other possible scenarios are shown in the following pictures and are
based on the inability to reach a node along the path of the LSP.
The below scenario postulates the usage of a reliable message
delivery based on the mechanism defined in [RFC2961].
| Path | | |
|--------------->| Path | |
| |---------------X| |
| |---------------X| |
| | ... | |
| |---------------X| |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 2: MP2CP - Path Msg and Communication Failure (reliable
delivery)
The Path message sent from LSR A towards LSR B is lost or does not
Caviglia, et al. Expires August 19, 2010 [Page 8]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
reach the destination for any reason. As a reliable delivery
mechanism is implemented, LSR A retransmits the Path message for a
configurable number of times and if no ack is received the handover
procedure will be aborted (via the Expiration timer).
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 | Path Tear | Path Tear |
|--------------->|--------------->|--------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 3: MP2CP - Path Msg and Communication Failure (no reliable
delivery)
If the Resv message is not received before the expiration of the
Expiration timer the handover procedure is aborted as described in
Section 4.2.1.1. Please note that any node that has forwarded a Path
(LSR A), i.e. has installed local path state, will send a PathTear
when that state is removed (accordingly to [RFC2205]).
4.2.2. MP to CP Handover Failure - Resv Error
4.2.2.1. MP to CP Handover Failure - Resv Error and Data Plane failure
In the case of failure occurrence during the Resv message processing,
(in case there has been any change in the data plane during the
signaling) the node MUST send a PathErr message [RFC2205] in the
upstream direction. The PathErr message is constructed and processed
as defined above in Section 4.2.1.1. The failure detection node MUST
also send a PathTear message downstream. The PathTear message is
constructed and processed as defined above in Section 4.2.1.1.
Caviglia, et al. Expires August 19, 2010 [Page 9]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| |X---------------| |
| PathErr | PathTear | PathTear |
|<---------------|--------------->|--------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 4: MP2CP - Resv Error and DP Failure
In the case shown in Figure 4, the failure occurs in LSR A. A
PathTear message is sent towards B and a PathErr message (with
ErrorCode set to "Handover Procedure Failure") is sent in the
upstream direction. The PathErr and PathTear messages remove the
Path state established by the Path messages along the nodes of the
LSP and abort the handover procedure.
Please note that the failure occurred after the handover procedure
was successfully completed in LSR B, but Handover state will still be
maintained locally as, per Section 4.1, a Path message with the H bit
clear will have not yet been sent or received. A node that receives
a PathTear when it has Path state with the H bit set MUST remove Path
state, but MUST NOT change data plane state. It MUST return LSP
ownership to the MP.
4.2.2.2. MP to CP Handover Failure - Resv Error and Communication
failure
When a Resv message cannot reach one or more of the upstream 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 the ingress Label
Edge Router (LER) or an LSR, say LSR A. LSR B MUST send a Resv
message again for a configurable number of times and then, if the
delivery does not succeed, the adoption procedure will be aborted
(via the Expiration timer).
Caviglia, et al. Expires August 19, 2010 [Page 10]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| | X---------| |
| | X---------| |
| | ... | |
| | X---------| |
| | | |
Ingress
LSR A LSR B Egress LER
Figure 5: MP2CP - Resv Error and Communication Failure (reliable
delivery)
Considering that the Resv message did not manage to reach LSR A, it
is highly probable that the PathErr would fail too. Due to this
fact, the Expiration timer is used on the Ingress LER after sending
the path and on LSR A after forwarding it. When the timer expires,
if no Resv or PathErr message is received, the handover procedure is
aborted as described in Section 4.2.1.1 and the LSP ownership
returned to the Management Plane.
Figure 6, on the other hand, shows the scenario in which no reliable
delivery mechanism is implemented.
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| | X---------| |
TIMER EXPIRES | | |
| Path Tear | Path Tear | Path Tear |
|--------------->|--------------->|--------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 6: MP2CP - Resv Error and Communication Failure (no reliable
delivery)
If non Resv message is received before the Expiration timer expires,
the ingress LER follows the same procedure defined in Section 4.1.
Caviglia, et al. Expires August 19, 2010 [Page 11]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
4.2.2.3. MP to CP Handover Failure - Node Graceful Restart
In the case of node restart and graceful restart is enabled then one
of the following scenarios will happen.
Case I - Finite Restart Time
In this case, the Restart Time (see [RFC3473]) is finite, i.e., not a
value of 0xffffffff. In the sequence diagram below, assume LSR A
restarts. If the ingress LER does not receive the Resv message in
time it MUST abort the handover 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 MUST start
tearing down all LSPs between LSR A and LSR B and this includes the
LSP that is being used to carry out the handover of MP resources to
CP. LSP B MUST generate a PathTear message downstream and a PathErr
message upstream. Both LSR B and the egress LER MUST NOT release the
DP resources because in both nodes the H bit is set in the local Path
state.
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| X X---------| |
| PathTear | |
|-------X Restart Timer |
| Expires |
| PathErr | PathTear |
| X--------|--------------->|
| | |
| X | |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 7: MP2CP - Node graceful restart - Case I
Case II - Infinite Restart Time
In this case, the Restart Time (see [RFC3473]) indicates that the
restart of the sender's control plane may occur over an indeterminate
interval, i.e., is 0xffffffff. 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
MUST start the recovery timer. The recovery timer will expire since
Caviglia, et al. Expires August 19, 2010 [Page 12]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
there will be no Path message with the RECOVERY LABEL received from
LSR A given the ingress node had already removed the local Path state
after it aborts the handover process. Thus LSR B MUST tear-down the
specific LSP that is being used to convert the MP resources to CP by
generating a PathTear message downstream and PathErr message
upstream. Similarly to the previous case both LSR B and the egress
LER MUST NOT release the DP resources because the H bit is set in the
local Path state.
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| X X---------| |
| PathTear | |
|-------X | |
| | |
| X | |
| | | |
| | Recovery Timer |
| | Expires |
| PathErr | PathErr | PathTear |
|<---------------|<---------------|--------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 8: MP2CP - Node graceful restart - Case II
Case III
In this case, the ingress LER does not abort the handover process.
When LSR A restarts, the ingress LER detects the restart and MUST re-
generate the Path message with the H bit set in order to re-start the
handover.
When LSR B receives the Path message, it sees the H-bit set on the
message and also sees that it has the H-bit set in its own state and
that it has sent the Resv. But it is also aware that LSR A has
restarted and could have sent a Path message with a RECOVERY LABEL
object. LSR B may attempt to resume the handover process or may
abort the handover. This choice is made according to local policy.
If resuming the handover, LSR B MUST treat the received Path message
as a retransmission, and MUST retransmit its Resv. If aborting
handover, LSR B MUST return a PathErr and MUST send a PathTear
Caviglia, et al. Expires August 19, 2010 [Page 13]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
downstream. In both cases, LSR B MUST NOT modify the DP state.
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| X X---------| |
| | |
| X | |
| | | |
| Path | Path | |
|--------------->|--------------->| |
| PathErr | PathErr | PathTear |
|<---------------|<---------------|--------------->|
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 9: MP2CP - Node graceful restart - Case III
4.3. 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 section we will analyze the
handover procedure success and failure.
The scenario is still a DP connection between two nodes acting as
ingress and egress for a LSP, but in this case the CP has the
ownership and control of the LSP. The CP to MP handover procedure
MUST delete the existing RSVP-TE session information and MUST NOT
affect the cross-connected resources, but just move their ownership
to the MP.
In other words, after LSP ownership transfer from CP to MP, the LSP
is no longer under control of RSVP-TE, which is no more able to "see"
the LSP itself. The CP to MP handover procedure MUST be a standard
LSP deletion procedure as described in Section 7.2.1 of [RFC3473].
The procedure is initiated at the ingress node of the LSP by a MP
entity. Ingress node and MP exchange the relevant information for
this task and then propagate it over CP by means of RSVP-TE tear down
signaling as described below.
The ingress node MUST send a Path message in the downstream direction
with Handover and Reflect bits set in the ADMIN_STATUS Object. No
action is taken over the DP and transit LSRs must forward such
Caviglia, et al. Expires August 19, 2010 [Page 14]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
message towards the egress node. All of the nodes MUST keep track of
the procedure storing the H bit in their local Path and Resv states.
Then every node waits for the H bit to be received within the related
Resv message. After the Resv message is received by the ingress LER,
it MUST send a PathTear message in order to clear the whole LSP
information recorded on the RSVP-TE data structures of the nodes.
Downstream nodes processing a PathTear message which follows a Path
message with the H bit set, MUST NOT remove any associated data plane
state. In other words, a normal LSP tear down signaling is exchanged
between nodes traversed by the LSP, but H bit set in the Path message
indicates that no DP action has to correspond to CP signaling.
4.4. CP to MP Handover Procedure Failure
Failures during CP to MP handover procedure MUST NOT result in the
removal of any associated data plane state. To that end, when a Resv
message containing an ADMIN_STATUS Object with the H bit is not
received during the period of time described in Section 7.2.2. of
[RFC3473] different processing is required. While the H bit is set
in the Path state, a node MUST NOT send a PathTear when a failure is
detected. Instead, the failure is reported upstream using a PathErr.
The only node that can send a PathTear is the ingress node, and it
can only do this as a step in the procedures specified in this
document. This applies to both MP to CP and CP to MP handover. The
ingress node MAY choose to report the failure in the CP to MP
handover procedure via the MP.
The CP to MP handover procedure can fail also due to two causes:
PathTear lost or node down. In the former case, if the LSP is not
under MP control after the Expiration Timer elapses, a manual
intervention from the network operator is requested, while in the
latter case different scenarios may happen:
- CASE I - Path message and node down
| Path | Path X |
|--------------->|--------------X |
| | |
| | X |
| | | |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 10: Case I - Path message and node down
Per [RFC3473] section 7.2.2 the ingress node should wait for a
Caviglia, et al. Expires August 19, 2010 [Page 15]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
configurable amount of time (30 seconds by default) and then send a
PathTear message. In this case the normal deletion procedure MUST
NOT be followed. When the Expiration timer elapses a manual
intervention from network operator is requested and normal, i.e., pre
CP to MP handover, LSP processing continues.
- CASE II - Resv message and node down
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| | | Resv |
| | Resv |<---------------|
| X X---------| |
| | |
| X | |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 11: Case II - Resv message and node down
The procedure to be followed is the same depicted in CASE I. The
network operator can ask for the automatic CP to MP procedure again
after the failed node comes back up. Per [RFC3473] section 7.2 the
nodes will forward the new Path and Resv messages correctly.
- CASE III - PathTear message and node down
| Path | Path | Path |
|--------------->|--------------->|--------------->|
| Resv | Resv | Resv |
|<---------------|<---------------|<---------------|
| PathTear | | |
|--------------->| PathTear X |
| |------------X |
| | X |
| | | |
Ingress LER LSR A LSR B Egress LER
Figure 12: Case III - PathTear message and node down
This scenario can be managed as a normal PathTear lost described
above in this section.
Caviglia, et al. Expires August 19, 2010 [Page 16]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
5. Minimum Information for MP to CP Handover
As described in Section 4, it is also possible for the ERO to contain
less than the full set of path information for the LSP being handed
over. This arises when only a minimal set of information is handed
to the CP by the MP at the LSP's head end. Instead of collecting all
of the LSP information (including the labels) and formatting it into
an ERO, as described in Section 4, it is possible to start with a
minimum amount of information. The full ERO method and the
partial/no ERO method are not mutually exclusive; support of both
methods are required.
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 egress node ID. The remaining information about an
existing LSP can then be collected hop by hop, as the signaling is
going on, by looking up the cross-connection table in DP at each node
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.
The Path message is hence built with the LABEL_SET 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 ADMIN_STATUS Object with H
bit set, as already defined in previous chapters 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 DP 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 LABEL_SET Object and UPSTREAM_LABEL Object content with
the looked-up values of upstream and downstream labels.
By repeating this procedure for each transit node along the LSP, it
is possible to make the handover Path message reach the egress node,
exactly following the LSP that is in place over DP. 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
Caviglia, et al. Expires August 19, 2010 [Page 17]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
port level with interface ID or the Label level with upstream and
downstream labels. The ERO can be used to check the consistency of
resource in DP down to the port level or label level at each
intermediate node along the LSP path.
Where the DP path continues beyond the egress, by indicating the
Egress label at the head-end of an LSP, the traffic can be directed
to the right destination. The GMPLS Signaling Procedure for Egress
Control is described in [RFC4003]
6. RSVP Message Formats
This memo does not introduce any modification in RSVP messages object
composition.
7. Objects Modification
The modifications required concern two RSVP objects: the ADMIN_STATUS
and the ERROR_SPEC Object.
7.1. Administrative Status Object
This memo introduces a new flag into the ADMIN_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) (25).
7.2. Error Spec Object
It is possible that a failure, such as the loss of DCN connection or
the restart of a node, occurs during the LSP ownership handing over.
In this case the LSP handover procedure is interrupted, the ownership
of the LSP must remain with the ownership prior to the initiation of
the handover procedure. It is important that the transaction failure
does not affect the DP. The LSP is kept in place and no traffic hit
occurs.
The failure is signaled by PathErr in the upstream direction and
PathTear Messages in the downstream direction. The PathErr messages
include an ERROR_SPEC Object specifying the causes of the failure.
This memo introduces a new Error Code (with different Error Values)
into the ERROR_SPEC Object, defined in [RFC2205].
The defined Error Code is "Handover Procedure Failure", and its value
is (TBD by IANA)(35). For this Error Code the following Error Values
Caviglia, et al. Expires August 19, 2010 [Page 18]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
are defined:
1 = Cross-connection mismatch
2 = Other failure
8. Compatibility
The main requirement for Handover procedure to work is that all nodes
along the path MUST support the extension defined in this draft.
This requirement translates to an administrative requirement as it is
not enforced at the protocol level. As defined, non-supporting nodes
will simply propagate the H bit without setting local state. This
may result in an impact on data traffic during the handover
procedure.
9. Security Considerations
The procedures described in this document rely completely on RSVP-TE
messages and mechanism. The use of H bit set in ADMIN_STATUS Object
basically informs the receiving entity that no operations are to be
done over DP 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 CP, making them not effective over
related DP resource usage.
However the handover procedures allow the control plane to be used to
take an LSP out of the control of the Management Plane. This could
cause considerable disruption and could introduce a new security
concern. As a consequence the use of GMPLS security techniques is
more important. For RSVP-TE Security please refer to [RFC3473],
while for GMPLS security framework please refer to [sec-fwk].
10. IANA Considerations
IANA has been asked to manage the bit allocations for the
ADMIN_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.
Bit Number Hex Value Name Reference
---------- ----------- ----------------------------------- ---------
25 0x00000040 Handover (H) [This.I-D]
Caviglia, et al. Expires August 19, 2010 [Page 19]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
IANA has also been asked to allocate a new error code:
35 Handover failure
This Error Code has the following globally-defined Error
Value sub-code:
1 = Cross-connection mismatch
2 = Other failure
11. Acknowledgments
We wish to thank Adrian Farrel, Lou Berger, Alan Elder, and Ben
Campbell for their assistance and precious advices to prepare this
draft for publication. We also wish to thank Nicola Ciulli
(Nextworks) who contributed to the 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
Francesco Fondelli
Ericsson
Via Negrone 1/A
Genova - 16145
Email: francesco.fondelli@ericsson.com
Lou Berger
LabN Consulting, LLC
Phone: +1 301 468 9228
EMail: lberger@labn.net
13. References
Caviglia, et al. Expires August 19, 2010 [Page 20]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[RFC4003] Berger, L., "GMPLS Signaling Procedure for Egress
Control", RFC 4003, February 2005.
13.2. Informational References
[RFC5493] Caviglia, D., Bramanti, D., Li, D., and D. McDysan,
"Requirements for the Conversion between Permanent
Connections and Switched Connections in a Generalized
Multiprotocol Label Switching (GMPLS) Network", RFC 5493,
April 2009.
[sec-fwk] Fang, L., "Security Framework for MPLS and GMPLS
Networks", July 2009.
Caviglia, et al. Expires August 19, 2010 [Page 21]
Internet-Draft RSVP-TE Ext for MP2CP LSP Handover February 2010
Authors' Addresses
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: diego.caviglia@ericsson.com
Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: daniele.ceccarelli@ericsson.com
Dino Bramanti
Ericsson
Dan Li
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Shenzhen 518129
P.R.China
Email: danli@huawei.com
Snigdho Bardalai
Fujitsu Network
2801 Telecom Parkway
Richrdson, Texas 75082
USA
Email: Snigdho.Bardalai@us.fujitsu.com
Caviglia, et al. Expires August 19, 2010 [Page 22]
