Internet DRAFT - draft-tanaka-pce-stateful-pce-data-ctrl
draft-tanaka-pce-stateful-pce-data-ctrl
PCE Working Group Y. Tanaka
Internet-Draft Y. Kamite
Intended status: Standards Track NTT Communications
Expires: August 17, 2014 I. Minei
Google
D. Dhody
Huawei Technologies
Feb 13, 2014
Stateful PCE Extensions for Data Plane Switchover and Balancing
draft-tanaka-pce-stateful-pce-data-ctrl-02
Abstract
Stateful Path Computation Element (PCE) and its corresponding
protocol extensions provide a mechanism that enables PCE to do
stateful control of Multiprotocol Label Switching (MPLS) Traffic
Engineering Label Switched Paths (TE LSP). One application that
stateful PCE can realize is data traffic reoptimization among the
LSPs. Data traffic traversed in a LSP can be switched to another
PCE-initiated LSP. Moreover, data traffic can be balanced to
multiple PCE-initiated LSPs and may also be policed based on a
signaling bandwidth of a PCE-Initiated LSP using stateful PCE.
This document specifies the extensions to Path Computation Element
Protocol (PCEP) that allow a stateful PCE to do switchover, balancing
and policing of data traffic with PCE-initiated LSPs. This document
also specifies the extensions, usage and handling of stateful PCEP
messages and the expected behavior of PCC as the RSVP-TE headend.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 17, 2014.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. PCEP Operation for Data Switchover and Balancing . . . . . . . 4
5. TLVs in LSP Objects . . . . . . . . . . . . . . . . . . . . . 6
5.1. ASSOCIATION-GROUP TLV in LSP Objects . . . . . . . . . . . 6
5.2. DATA-CONTROL TLV in LSP Objects . . . . . . . . . . . . . 8
5.3. DATA-REPORT TLV in LSP Objects . . . . . . . . . . . . . . 10
5.4. Advertising Support of Data Switchover and Balancing . . . 11
6. Operation Examples . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Data switchover operation (100:0 => 0:100) . . . . . . . . 11
6.2. Load balancing operation (100:0 => 50:50) . . . . . . . . 13
6.3. Load balancing operation (100:0 => 66:33) . . . . . . . . 14
7. Redundant stateful PCEs . . . . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8.1. Malicious PCE . . . . . . . . . . . . . . . . . . . . . . 16
8.2. Malicious PCC . . . . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. PCEP TLV Indicators . . . . . . . . . . . . . . . . . . . 17
9.2. PCEP Error Objects . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
[I-D.ietf-pce-stateful-pce] describes the stateful Path Computation
Elements (PCE) procedures and defines the extensions to PCEP to
enable stateful control of LSPs between and across PCEP sessions,
further it also describes mechanisms to effect LSP state
synchronization between PCCs and PCEs, and PCE control of timing and
sequence of path computations within and across PCEP sessions. A PCE
can update LSP settings (such as bandwidth, priority, path) using an
update message (called PCUpd).
[I-D.ietf-pce-pce-initiated-lsp] defines the extensions to PCEP to
allow a PCE to instantiate new LSPs (called PCE-Initiated LSPs).
Before these extensions, the LSP ingress point had to be
preconfigured at the head end Label Edge Router (LER), the LSP
control automatically delegated to the initiating stateful PCE and
then its parameters (e.g., bandwidth, priority, path) could be
modified via a PCUpd message. The extensions for PCE-initiated LSPs
eliminate the need for preconfiguration, and allow more flexible
operations on the network. Stateful-PCE with LSP instantiation is
attracting attention as an enabler for Software Defined Networking
(SDN) operation of MPLS networks.
In SDN, it is highly expected to support intelligent and interactive
control of the amount of network traffic by means of a logically-
centralized controller. Optimizing the path and bandwidth of MPLS-TE
LSP by using stateful PCE is a leading use case of SDN applications.
A PCE is able to calculate an optimized route from the topology and
bandwidth information in the Traffic Engineering Database (TED) and
the LSP state database (LSPDB) and it can integrate with a controller
that takes into account additional information such as historical
trends and service orders to trigger some PCE actions. For example,
when data traffic on a LSP increases the bandwidth utilization and if
there is no capacity left in the currently signaled path (i.e., no
remaining bandwidth of links), a PCE is able to update the existing
LSP's parameters (PCE-updated LSP) or create a totally new LSP (PCE-
initiated LSP).
The former method is oriented for keeping the existing instance of
LSP tunnel. Meanwhile, the latter method is oriented for adding a
new instance of a LSP tunnel.
Specifically regarding the latter method, PCE-initiated LSP, there
are some operational scenarios in the network: one is that PCE
instantiate a new LSP that have alternate route with increased-
bandwidth LSP and performs switchover from old LSP. Another is that
PCE creates one or more additional LSPs and performs load balancing
of data traffic. Today, however, there is no detailed procedure
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specified as to how to control data traffic switching from an old LSP
to new PCE-Initiated LSP(s).
For another example, when data traffic on a LSP increases its
bandwidth utilization and if there is strict traffic contract, a PCE
is able to force a PCC not to exceed the contract bandwidth.
This document specifies the procedures that a stateful PCE can use to
control data traffic switchover, load balancing with multiple PCE-
Initiated LSPs and policing activation/deactivation. This document
also specifies the usage and handling of stateful PCEP messages and
the expected behavior of PCC as an RSVP-TE headend.
2. Conventions used in this document
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[RFC2119].
3. Terminology
This document uses the following terms defined in [RFC5440]: PCC,
PCE, PCEP Peer.
This document uses the following terms defined in
[I-D.ietf-pce-stateful-pce]: Stateful PCE, LSP State Request, LSP
Update Request.
This document uses the following terms defined in
[I-D.ietf-pce-pce-initiated-lsp]: LSP Initiate Message.
4. PCEP Operation for Data Switchover and Balancing
There are two typical operations for explaining the functionality of
data switchover and balancing.
o Whole data switchover, where a PCC switches all data traffic from
one LSP tunnel to another.
o Load balancing of multi-instance LSP tunnels with different paths,
where a PCC (headend) balances data traffic among two or more
tunnels (ex fifty percent each, for two instances).
Both operational cases are completed by the messaging over a single
protocol, PCEP, keeping this as a simple and straightforward solution
for MPLS networks.
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A PCEP speaker indicates its ability to support PCE control over the
data switchover and balancing during the PCEP Initialization phase.
The Open Object in the Open message contains the "Stateful PCE
Capability" TLV, defined in [I-D.ietf-pce-stateful-pce]. A new flag,
the W (LSP-DATASWITCHOVER-BALANCE-CAPABILITY) flag is introduced. A
PCE can control the data switchover and loadbalancing only for PCCs
that advertised this capability and a PCC will follow the procedures
described in this document only on sessions where the PCE advertised
the W flag. (Refer Section 5.4)
Data switchover and balancing for an MPLS-TE LSP is available once a
PCEP session is established and then a PCC delegates its LSPs to a
PCE.
First step is LSP instantiation. In this step, a PCE sends as many
PCInitiate messages as PCE-Initiated LSP as per demand. Once the PCC
receives them and successfully establishes PCE-Initiated LSPs, it
sends PCRpt messages in reply to the PCInitiate messages and
delegates the newly established LSP to the PCE. Message formats and
behaviors of the PCC and the PCE are described in detail in
[I-D.ietf-pce-pce-initiated-lsp].
Second step is LSP association. After the PCE-Initiated LSP
successfully established and delegated the PCE sends a PCUpd message
that contains the ASSOCIATION-GROUP TLV in the LSP Object in order to
assemble the members of an association group of LSPs to take over the
traffic. Once a PCC receives the PCUpd message with ASSOCIATION-
GROUP TLV, the PCC sends back a PCRpt message that contains the
ASSOCIATION-GROUP TLV with current operational status.
[Editor's Note: The option of specifying the association at LSP
instantiation time (as part of the PCInitiate message) will be
evaluated in a future version of this document.]
Third step is executing the data switchover and/or load balancing.
In this step, the PCE sends a single PCUpd message which updates the
operational status of the LSP from "up and carrying traffic" to just
"up". This Update request message for data plane switchover/
balancing execution MUST contain DATA-CONTROL TLV in LSP Object. The
associated group of traffic origin and that of target to take over
the traffic are listed in the DATA-CONTROL TLV. The PCC (LSP
headend) load-balances between LSPs in the same association group
based on their respective bandwidths. The switchover case is
supported since there will be an association of a single LSP, so that
LSP will get hundred percent of data traffic.
The PCC MUST send a PCRpt message to the PCE in order to notify of
the result of the data switchover/balancing. The PCRpt message MUST
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have the DATA-CONTROL TLV that indicates the actual assigned
percentages of each member of association group after the execution
of the data switchover/balancing operation. The LSP object in the
PCRpt will have the reserved PLSP-ID of 0.
The final step is the deletion of old LSP. It is OPTIONAL to carry
out this step. The PCE sends PCInitiate message requesting deletion
of the LSP that does not carry data traffic anymore after data
switchover/balancing execution. Once the PCC tears down the LSP, a
PCRpt message MUST be sent from the PCC to the PCE in order to notify
that the LSP is no longer used.
Note that, both RSVP-TE [RFC3209] Tunnel-ID and LSP-ID for PCE-
Initiated LSP signaling is not allocated by a PCE. A PCC locally
assigns those IDs that are related to RSVP-TE parameters. Therefore,
the operations of data switchover and balancing specified in this
document is the traffic control procedure across multiple RSVP-TE
Tunnels (i.e., different Tunnel instances). Data switchover method
across LSPs within a single RSVP-TE Tunnel, which is the switchover
in the middle of make-before-break reoptimization, is covered by
[I-D.tanaka-pce-stateful-pce-mbb].
5. TLVs in LSP Objects
5.1. ASSOCIATION-GROUP TLV in LSP Objects
This section defines ASSOCIATION-GROUP TLV in LSP Objects. An
ASSOCIATION-GROUP TLV is used in the LSP Object in PCUpd messages
when a PCE creates an association group of LSPs on a PCC. Further it
is used in a LSP object in a PCRpt message to confirm the
association.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Group ID | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Group ID | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ASSOCIATION-GROUP TLV format
Flags and fields
Association Group ID - 24 bits: This field specifies a
identifier of association group of LSPs. The IDs are assigned
by a PCE. 0x000000 and 0xFFFFFF is reserved for special use.
Flags - 8 bit: None defined. MUST be set to zero.
An association group is a group of LSPs that is referenced by a
single identifier, by both the PCE and PCC. This number is
significant in the context of a single PCEP session. An association
group may have one or more LSPs. Association groups with zero
members are removed and the id can be reused. The PCE is the entity
managing association, and this is considered PCE's state that will be
cleaned up when the State Timeout Interval expires.
The status of the association group is active when the group is up
and carrying data traffic. Otherwise, it is inactive when the group
does not carry any data traffic. An LSP is able to associate with up
to two association groups, unless both association groups are active
at any given point in time. This is done to allow a new LSP to be
instantiated and assigned with a new inactive association group, the
existing LSP is also associated with this group. This allows
switching to the new group.
To create a new association group on a PCC, a PCE sends a PCUpd
message which contains the LSP Object(e.g. PLSP-ID=100) and
ASSOCIATION-GROUP TLV (Association Group ID=10) in the LSP object.
Next, a PCE sends the another PCUpd message with another LSP
Object(e.g. PLSP-ID=200) and ASSOIATION-GROUP TLV(Association Group
ID=10). As a result, the PCC and PCE both recognize that Association
Group ID 10 represents PLSP-ID=100 and 200.
To remove a specific PLSP-ID from the association group, a PCE sends
PCUpd message which contains the LSP Object(PLSP-ID=100) and
ASSOCIATION-GROUP TLV (Association Group ID=0x0000). Then a PCC
removes the PLSP-ID 100 from any inactive association group on the
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PCC.
To flush all association groups on a PCC, a PCE sends a PCUpd message
which contains the LSP Object(PLSP-ID=0x0000) and ASSOCIATION-GROUP
TLV(Association Group ID=0x0000). Then a PCC flushes all association
groups. A traffic handling behavior of a PCC when it flushes the
active association group is left for a future version of this
document.
To associate a PLSP-ID with the existing inactive association group,
A PCE sends a PCUpd message which contains the PLSP-ID and the
existing Association Group ID. A PCE is not allowed to add any
PLSP-ID to the active association group in order to avoid rebalancing
traffic without data-ctrl requests. If the PCUpd message contains a
PLSP-ID and the active Association Group ID, the PCC MUST send out a
PCErr with error value TBD to indicate an invalid operation.
When the LSP of the active association group is torn down by a reason
of either network failure or administrative down-request from the
PCE, a PCC MUST remove the PLSP-ID from the group and rebalance the
traffic based on the respective bandwidths of the rest of LSPs.
After rebalancing, The PCC MUST report the actual percentage to the
PCE using PCRpt with DATA-REPORT TLV (Section 5.3).
Note that a PCE is able to associate not only PCE-Initiated LSP but
also existing LSP(i.e., PCE-updated LSP) with any association group
on a PCC.
The definition of PCRpt messages when a PCC creates/removes/flushes
an association group will be clarified in the future version of this
draft. Redundant stateful PCE section needs the PCRpt in order to
sync the association group IDs and actual percentages of balancing.
5.2. DATA-CONTROL TLV in LSP Objects
This section defines DATA-CONTROL TLV in LSP Objects. A DATA-CONTROL
TLV is used in the LSP Object in PCUpd messages when a PCE makes a
PCC to execute traffic switchover or load balancing. It is also
mandatory in a LSP object in a PCRpt message with DATA-REPORT TLV to
notify the results of execution.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Origin Association Group ID | Flags | O |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target Association Group ID | Flags |P| O |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DATA-CONTROL TLV format
Flags and fields
Origin Association Group ID - 24 bits: data traffic origin
Target Association Group ID - 24 bits: for taking over whole
data traffic from origin.
P (Policing - 1 bit: This flag is used when a PCE makes a PCC
apply traffic policer. If this flag is set 1, traffic
exceeding the bandwidth of the LSP is discarded on the PCC
after traffic switchover execution. Otherwise, the PCC does
not apply any traffic policer and traffic on a target
association group will not be discarded.
O (Operational - 3 bits): This flag represents the requested
operational status for each Origin Association Group ID and
Target Association Group ID by a PCE when this TLV is used in a
PCUpd message. It is also used as a status report in a PCRpt
message. The meanings of the values are defined in
[I-D.ietf-pce-stateful-pce].
An LSP Object in a PCUpd message MUST have DATA-CONTROL TLV when a
PCE operates data switchover and balancing on a PCC. DATA-CONTROL
TLV is sub-TLV of an LSP Object and is used in both a PCUpd and a
PCRpt message.
An operation of data switchover/balancing is the action of
transferring traffic from an origin association group to a target
association group. A PCUpd message with reserved LSP Object (PLSP-
ID=0x00000) and DATA-CONTROL TLV (a set of an origin and a target
association group) MUST triggers data switchover/balancing execution.
Traffic policer is able to be applied in both traffic switchover case
and load-balancing case.
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5.3. DATA-REPORT TLV in LSP Objects
This section defines DATA-REPORT TLV in LSP Objects. A DATA-REPORT
TLV is used in the LSP Object in PCRpt message to notify the results
of execution with the DATA-CONTROL TLV.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member 1 (PLSP-ID ) | Flags | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member 2 (PLSP-ID ) | Flags | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member N (PLSP-ID ) | Flags | Percentage |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DATA-REPORT TLV format
Flags and fields
Member(PLSP-ID) - 20 bit: This TLV is only used in a PCRpt
message and represents actual percentages of load balancing per
respective PLSP-ID after load balancing execution. Member
field fills PLSP-ID that is member of target association group.
As per [I-D.ietf-pce-stateful-pce].
Flags - 5 bit: None defined. MUST be set to zero.
Percentage - 7 bits: This field specifies actual percentage of
load balancing as a closest integer, with 100% as the max
allowed value.
A PCC replies to a PCE a PCRpt message as an acknowledgment of data
switchover/balancing result. The PCRpt message MUST have reserved
LSP Object(PLSP-ID=0x00000) and DATA-CONTROL TLV with DATA-REPORT TLV
inside.
The PCC load-balances between LSPs in the same association group
based on their respective bandwidths.If one of the LSPs goes down by
network failure, the traffic would load-balance correctly over the
others. If a PCE updates the bandwidth of the LSP, the traffic would
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rebalance after a PCC completes the signaling. If one of the LSPs is
signaled with zero bandwidth, no traffic would be transferred to the
LSP. If all LSPs of the association group are signaled with zero
bandwidth, the traffic would load-balance equally. In switchover
case, the hundred percent traffic will be transferred to the LSP even
if the LSP is zero bandwidth.
The traffic on the existing LSP is able to load-balance over both the
existing LSP itself and new PCE-Initiated LSPs, by means of that the
existing LSP belongs to both the origin association group and that of
target.
5.4. Advertising Support of Data Switchover and Balancing
New flags are defined for the STATEFUL-PCE-CAPABILITY TLV defined in
[I-D.ietf-pce-stateful-pce].
W (LSP-DATASWITCHOVER-BALANCE-CAPABILITY - 1 bit): if set to 1 by a
PCEP speaker, it indicates that the PCEP speaker allows data
switchover and balancing.
6. Operation Examples
For easy understanding this section introduces typical operation
examples of data switchover/balancing.
6.1. Data switchover operation (100:0 => 0:100)
A PCE instructs a PCC to switchover 100% traffic from association
group ID 1 to association group ID 2. A PCE sends single PCUpd
message containing the mandatory LSP Objects with DATA-CONTROL TLV.
Expected PCUpd, PCRpt messages to create association group and to
trigger data switchover follow.
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PCE PCC(Ingress) Egress
[LSP Association for existing LSP]
| | |
| --PCUpd ----------------->| |
| LSP Obj: PLSP-ID=1 | |
| + ASSOC-G: Assoc-G-ID 10| |
| | |
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=1 | |
| + ASSOC-G: Assoc-G-ID 10| |
[LSP Creation]
| | |
| --PCInitiate ------------>| |
| | --Path ------->|
| |<------- Resv-- | Establish a new
|<--PCRpt ----------------- | | PCE-Initiated LSP
| LSP Obj: PLSP-ID=2 | |
| | |
[LSP Association for PCE-Initiated LSP]
| | |
| --PCUpd ----------------->| |
| LSP Obj: PLSP-ID=2 | |
| + ASSOC-G: Assoc-G-ID 20| |
| | |
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=2 | |
| + ASSOC-G: Assoc-G-ID 20| |
| | |
[Switchover Execution]
| | |
| --PCUpd ----------------->| |
| LSP Obj: PLSP-ID=0x0000 | |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) : |
| Target Assoc-G-ID 20(O=active) : |
| |))))))))))))))))| Switchover
| |}}}}}}}}}}}}}}}}| Execution
|<--PCRpt------------------ | : |
| LSP Obj: PLSP-ID=0x0000 | : |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) |
| Target Assoc-G-ID 20(O=active) |
| + D-REPORT: | |
| PLSP-ID 2, 100% | |
| | |
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Figure 4: Switchover Operation Example
6.2. Load balancing operation (100:0 => 50:50)
The scenario is one where the starting state is a single LSP (of
bandwidth 100 M) is carrying the traffic. To enable better bin-
packing, the PCE may want to create two smaller LSPs instead, each of
50M, and load balance the traffic over them. To accomplish this, two
association groups are used, the first (say association group ID 10)
contains the LSP carrying the traffic, and the second (say
association group ID 30) contains the two new smaller LSPs. Expected
PCUpd, PCRpt messages to create association group and to trigger
load-balance follow (The instantiation of the original LSP of
bandwidth 100M and its association into group ID 10 is not shown)
PCE PCC(Ingress) Egress
[LSP Creation]
| | |
| --PCInitiate x2---------->| |
| BW: 50M | --Path x2----->|
| |<-----Resv x2-- | Establish two new
|<--PCRpt ----------------- | | PCE-Initiated LSP
| LSP Obj: PLSP-ID=3 | |
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=4 | |
| | |
[LSP Association for PCE-Initiated LSPs]
| | |
| --PCUpd ----------------->| | Create new
| LSP Obj: PLSP-ID=3 | | Association Group
| + ASSOC-G: Assoc-G-ID 30| | for PCE-Initiated
| | | LSP
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=3 | |
| + ASSOC-G: Assoc-G-ID 30| |
| | |
| --PCUpd ----------------->| | Add a new LSP
| LSP Obj: PLSP-ID=4 | | to Association Group
| + ASSOC-G: Assoc-G-ID 30| |
| | |
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=4 | |
| + ASSOC-G: Assoc-G-ID 30| |
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[Load Balancing Execution]
| --PCUpd------------------>| |
| LSP Obj: PLSP-ID=0x0000 | |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) : |
| Target Assoc-G-ID 30(O=active) : |
| |))))))))))))))))| Balancing
| |)})})})})})})})}| Execution
| | : |
|<--PCRpt------------------ | : |
| LSP Obj: PLSP-ID=0x0000 | : |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) |
| Target Assoc-G-ID 30(O=active) |
| + D-REPORT: | |
| PLSP-ID 3, 50% | |
| PLSP-ID 4, 50% | |
| | |
Figure 5: Load-Balance Operation Example
6.3. Load balancing operation (100:0 => 66:33)
The scenario is one where the starting state is a single LSP (of
bandwidth 100 M) is carrying the traffic. But as the data traffic
load increases another 50 M is required. The PCE may want to create
another LSP of 50 M, and load balance the traffic over the existing
and new LSP. To accomplish this, two association groups are used,
the first (say association group ID 10) contains the LSP carrying the
traffic, and the second (say association group ID 40) contains the
new initiated LSP as well as the original LSP. Expected PCUpd, PCRpt
messages to create association group and to trigger load-balance
follow (The instantiation of the original LSP of bandwidth 100M and
its association into group ID 10 is not shown)
PCE PCC(Ingress) Egress
[LSP Creation]
| | |
| --PCInitiate ------------>| |
| BW: 50M | --Path ------->|
| |<-----Resv ---- | Establish new
|<--PCRpt ----------------- | | PCE-Initiated LSP
| LSP Obj: PLSP-ID=5 | |
| |
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[LSP Association for PCE-Initiated LSPs]
| | |
| --PCUpd ----------------->| | Create new
| LSP Obj: PLSP-ID=5 | | Association Group
| + ASSOC-G: Assoc-G-ID 40| | for PCE-Initiated
| | | LSP
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=5 | |
| + ASSOC-G: Assoc-G-ID 40| |
| | |
| --PCUpd ----------------->| | Add the old LSP
| LSP Obj: PLSP-ID=1 | | to the Association
| + ASSOC-G: Assoc-G-ID 40| | Group
| | |
|<--PCRpt ----------------- | |
| LSP Obj: PLSP-ID=1 | |
| + ASSOC-G: Assoc-G-ID 40| |
[Load Balancing Execution]
| --PCUpd------------------>| |
| LSP Obj: PLSP-ID=0x0000 | |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) : |
| Target Assoc-G-ID 40(O=active) : |
| |))))))))))))))))| Balancing
| |)})})})})})})})}| Execution
| | : |
|<--PCRpt------------------ | : |
| LSP Obj: PLSP-ID=0x0000 | : |
| + D-CTRL: | : |
| Origin Assoc-G-ID 10(O=up) |
| Target Assoc-G-ID 40(O=active) |
| + D-REPORT: | |
| PLSP-ID 1, 66% | |
| PLSP-ID 5, 33% | |
| | |
Figure 6: Load-Balance Operation Example
7. Redundant stateful PCEs
Association group IDs are unique within a PCEP session across the
primary PCE and the PCC. A backup PCE has to synchronize the
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association group IDs, PCE that created the association group and
balancing percentages in advance of the failure on the primary PCE.
One practical method to synchronize is a PCC replicates each PCRpt
message for the backup PCEP session. A backup PCE is able to receive
the association group IDs from ASSOCIATION-GROUP TLV and the result
of balancing percentages from DATA-REPORT TLV.
8. Security Considerations
This document defines extensions to PCEP to control load balancing of
traffic across multiple LSPs or to completely switch traffic from one
LSP to another. The nature of these extensions results in more
information being available for a hypothetical adversary and a number
of additional attack surfaces which must be protected. As a general
precaution, it is RECOMMENDED that these PCEP extensions only be
activated on authenticated and encrypted sessions across PCEs and
PCCs belonging to the same administrative authority
In addition to the security considerations and recommendations
described in [I-D.ietf-pce-stateful-pce], the following also apply.
8.1. Malicious PCE
A malicious PCE may flap the traffic between several LSPs, creating
shifting patterns in the network and excessive load on the PCC. A
PCC may protect itself from such an attack by enforcing a limit on
the number of data-control requests per unit of time and MAY take
additional steps ranging from delegation revocation to closing the
PCEP session.
8.2. Malicious PCC
Because the PCE keeps state regarding LSP associations for all the
PCCs, it is RECOMMENDED that the PCE have a bound on the amount of
state each PCC can occupy, and in the context of this draft, the
number of associations on a PCC and the number of associations each
LSP may be part of. Otherwise, a malicious PCC may create an
unbounded number of associations. Additionally, a malicious PCC may
purposely fail data-control messages in order to force the PCE to
continuously resend them and create artificial load on the PCE. The
PCE may protect itself from these situations by placing a limit on
the number of failures and closing the PCEP session.
9. IANA Considerations
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9.1. PCEP TLV Indicators
This document defines the following new PCEP TLVs:
Value Meaning Reference
TBD DATA-CONTROL This document
TBD DATA-REPORT This document
9.2. PCEP Error Objects
This document defines new Error-Type and Error-Value for the
following new error conditions:
Error-Type Meaning
6 Mandatory Object missing
Error-value=TBD: DATA-CONTROL TLV missing.
Error-value=TBD: DATA-REPORT TLV missing.
19 Invalid operation
Error-value=TBD: No association group existing.
Error-value=TBD: No association group specified.
Error-value=TBD: No PLSP can be added to
the active association group.
10. Acknowledgments
Many thanks to Adrian Farrel for their ideas and suggestions.
11. References
11.1. Normative References
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-00 (work in
progress), December 2013.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE",
draft-ietf-pce-stateful-pce-07 (work in progress),
October 2013.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
11.2. Informative References
[I-D.tanaka-pce-stateful-pce-mbb]
Tanaka, Y. and Y. Kamite, "Make-Before-Break MPLS-TE LSP
restoration and reoptimization procedure using Stateful
PCE", draft-tanaka-pce-stateful-pce-mbb-02 (work in
progress), October 2013.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
Authors' Addresses
Yosuke Tanaka
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: yosuke.tanaka@ntt.com
Yuji Kamite
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: y.kamite@ntt.com
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Ina Minei
Google
US
Email: inaminei@google.com
Dhruv Dhody
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
Email: dhruv.ietf@gmail.com
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