Internet DRAFT - draft-ietf-pwe3-iccp-stp
draft-ietf-pwe3-iccp-stp
INTERNET-DRAFT Mingui Zhang
Intended Status: Proposed Standard Huafeng Wen
Expires: April 11, 2016 Huawei
Jie Hu
China Telecom
October 9, 2015
Spanning Tree Protocol (STP) Application
of Inter-Chassis Communication Protocol (ICCP)
draft-ietf-pwe3-iccp-stp-05.txt
Abstract
Inter-Chassis Communication Protocol (ICCP) supports an inter-chassis
redundancy mechanism which is used to support high network
availability.
In this document, Provider Edge (PE) devices in a Redundancy Group
(RG) running ICCP are used to offer multi-homed connectivity to
Spanning Tree Protocol (STP) networks to improve availability of the
STP networks. The ICCP TLVs and usage for the ICCP STP application
are defined.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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Copyright and License Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions used in this document . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Spanning Tree Protocol Application TLVs . . . . . . . . . . . . 6
3.1. STP Connect TLV . . . . . . . . . . . . . . . . . . . . . . 6
3.2. STP Disconnect TLV . . . . . . . . . . . . . . . . . . . . 7
3.2.1. STP Disconnect Cause sub-TLV . . . . . . . . . . . . . 7
3.3. STP Config TLVs . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1. STP System Config . . . . . . . . . . . . . . . . . . . 8
3.3.2. STP Region Name . . . . . . . . . . . . . . . . . . . . 9
3.3.3. STP Revision Level . . . . . . . . . . . . . . . . . . 10
3.3.4. STP Instance Priority . . . . . . . . . . . . . . . . . 11
3.3.5. STP Configuration Digest . . . . . . . . . . . . . . . 11
3.4. STP State TLVs . . . . . . . . . . . . . . . . . . . . . . 12
3.4.1. STP Topology Changed Instances . . . . . . . . . . . . 12
3.4.2. STP CIST Root Time Parameters . . . . . . . . . . . . . 13
3.4.3. STP MSTI Root Time Parameter . . . . . . . . . . . . . 15
3.5. STP Synchronization Request TLV . . . . . . . . . . . . . . 15
3.6. STP Synchronization Data TLV . . . . . . . . . . . . . . . 17
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Common AC Procedures . . . . . . . . . . . . . . . . . . . 18
4.1.1. Remote PE Node Failure or Isolation . . . . . . . . . . 18
4.1.2. Local PE Isolation . . . . . . . . . . . . . . . . . . 18
4.2. ICCP STP Application Procedures . . . . . . . . . . . . . . 19
4.2.1. Initial Setup . . . . . . . . . . . . . . . . . . . . . 19
4.2.2. Configuration Synchronization . . . . . . . . . . . . . 20
4.2.3. State Synchronization . . . . . . . . . . . . . . . . . 20
4.2.4. Failure and Recovery . . . . . . . . . . . . . . . . . 21
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 22
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 22
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 23
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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7.1. Normative References . . . . . . . . . . . . . . . . . . . 23
7.2. Informative References . . . . . . . . . . . . . . . . . . 23
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
Inter-Chassis Communication Protocol (ICCP [RFC7275]) specifies a
multi-chassis redundancy mechanism which enables Provider Edge (PE)
devices located in a multi-chassis arrangement to act as a single
Redundancy Group (RG).
With the Spanning Tree Protocol (STP), a spanning tree will be formed
over connected bridges by blocking some links between these bridges
so that forwarding loops are avoided. This document introduces
support of STP as a new application of ICCP. This STP application of
ICCP supports when a bridged STP network is connected to a RG, the RG
members act as a single root bridge participating in the operations
of STP protocol.
STP relevant information needs to be exchanged and synchronized among
the RG members. New ICCP TLVs for the ICCP STP application are
specified for this purpose.
From the point of view of the customer, the Service Provider is
providing a Virtual Private LAN Service (VPLS) [RFC4762].
1.1. 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 RFC 2119 [RFC2119].
1.2. Terminology
ICCP: Inter-Chassis Communication Protocol
VPLS: Virtual Private LAN Service
STP: Spanning Tree Protocol
MSTP: Multiple Spanning Tree Protocol
MST: Multiple Spanning Trees
CIST: Common and Internal Spanning Tree ([802.1q] Section 3.27)
MSTI: Multiple Spanning Tree Instance ([802.1q] Section 3.138)
BPDU: Bridge Protocol Data Unit
In this document, unless otherwise explicitly noted, the term STP
also covers MSTP.
2. Use Case
Customers widely use Ethernet as an access technology [RFC4762]. It's
common that one customer's Local Area Network (LAN) has multiple
bridges connected to a carrier's network at different locations for
reliability purposes. Requirements for this use case are listed as
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follows.
o Customers desire to balance the load among their available
connections to the carrier's network, therefore all the
connections need to be active.
o When one connection to the carrier network fails, customers
require a connection in another location to continue to work after
the re-convergence of the STP rather than compromising the whole
STP network. The failure of the connection may be due to the
failure of the PE, the attachment circuit (AC) or even the
Customer Edge (CE) device itself.
In order to meet these requirements, the 'ICCP-STP' model is
proposed. It introduces STP as a new application of ICCP.
+--------------+ +=============+
| | | |
| | | |
| +---+ | | +-----+|<--|--Pseudowire-->|
| +---+CE1+<6>-------<5>+ PE1 || | |
| <1> +---+ | | +-----+|<--|--Pseudowire-->|
| +-+-+ | | || |
| |CE3| | | ||ICCP |--> Towards the Core
| +-+-+ | | || |
| <2> +---+ | | +-----+|<--|--Pseudowire-->|
| +---+CE2+<3>-------<4>+ PE2 || | |
| +---+ | | +-----+|<--|--Pseudowire-->|
| | | |
| Multi-homed | | Redundancy |
| STP Network | | Group |
+--------------+ +=============+
Figure 2.1: A STP network is multihomed to RG running ICCP.
Figure 2.1 shows an example topology of this model. With ICCP, the
whole RG will be virtualized to be a single bridge. Each RG member
has its BridgeIdentifier (the MAC address). The numerically lowest
one is used as the BridgeIdentifier of the 'virtualized root bridge'.
The RG acts as if the ports connected to the STP network (port <4>,
<5>) are for the same root bridge. All these ports send the
configuration BPDU with the highest root priority to trigger the
construction of the spanning tree. The link between the peering PEs
is not visible to the bridge domains of the STP network. In this way,
the STP will always break a possible loop within the multi-homed STP
network by breaking the whole network into separate islands so that
each is attached to one PE. That forces all PEs in the RG to be
active. This is different from a generic VPLS [RFC4762] where the
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root bridge resides in the customer network and the multi-homed PEs
act in the active-standby mode. Note that the specification of VPLS
remains unchanged other than for this operation. For instance, a
full-mesh of pseudowires (PWs) is established between PEs, and split-
horizon is still used to perform the loop-breaking through the core.
3. Spanning Tree Protocol Application TLVs
This section specifies the ICCP TLVs for the ICCP STP application.
The Unknown TLV bit (U-bit) and the Forward unknown TLV bit (F-bit)
of the following TLVs MUST be sent as cleared and processed on
receipt as specified in [RFC7275].
3.1. STP Connect TLV
This TLV is included in the RG Connect message to signal the
initiation of ICCP STP application connection.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol Version |A| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Sub-TLVs |
~ ~
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA1 (value to be assigned by IANA) for "STP Connect TLV"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- Protocol Version
The version of STP ICCP application protocol. This document
defines version 0x0001.
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- A bit
Acknowledgement Bit. Set to 1 if the sender has received a STP
Connect TLV from the recipient. Otherwise, set to 0.
- Reserved
Reserved for future use. These bits MUST be sent as zero and
ignored on receipt.
- Optional Sub-TLVs
There are no optional Sub-TLVs defined for this version of the
protocol.
3.2. STP Disconnect TLV
This TLV is used in RG Disconnect Message to indicate that the
connection for the ICCP STP application is to be terminated.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA2 for "STP Disconnect TLV"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- Optional Sub-TLVs
The only optional Sub-TLV defined for this version of the
protocol is the "STP Disconnect Cause" sub-TLV, defined below:
3.2.1. STP Disconnect Cause sub-TLV
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA13 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Disconnect Cause String |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA13 for "STP Disconnect Cause TLV"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- Disconnect Cause String
Variable length string specifying the reason for the disconnect,
encoded in UTF-8 [RFC3629] format. Used for operational
purposes.
3.3. STP Config TLVs
The STP Config TLVs are sent in the RG Application Data message. When
STP Config TLV is received by a peer RG member, it MUST synchronize
the configuration information contained in the TLV. TLVs specified
from Section 3.3.1 through Section 3.3.5 defines specific
configuration information.
3.3.1. STP System Config
This TLV announces the local node's STP System Parameters to the RG
peers.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ROID |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA3 for "STP System Config"
- Length
Length of the ROID plus the MAC address in octets. Always set to
14.
-ROID
Redundant Object Identifier, format defined in Section 6.1.3 of
[RFC7275].
- MAC Address
The MAC address of the sender. This MAC address is set to the
BridgeIdentifier of the sender, as defined in [802.1q] Section
13.26.2. The numerically lowest 48 bit unsigned value of
BridgeIdentifier is used as the MAC address of the Virtual Root
Bridge mentioned in Section 2.
3.3.2. STP Region Name
This TLV carries the value of Region Name.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Region Name |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA4 for "STP Region Name"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- Region Name
The Name of the MST Region as specified in [802.1q] Section
3.142.
3.3.3. STP Revision Level
This TLV carries the value of Revision Level.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Revision Level |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
Set to TBA5 for "STP Revision Level".
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields. Always set to 2.
- Revision Level
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The Revision Level as specified in [802.1q] Section 13.8 bullet
c));
3.3.4. STP Instance Priority
This TLV carries the value of Instance Priority to other members in
the RG.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA6 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pri | InstanceID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA6 for "STP Instance Priority"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- Pri
The Instance Priority. It is interpreted as unsigned integer
with higher value indicating a higher priority.
- InstanceID
The 12 bits Instance Identifier of the CIST or MSTI. This
parameter takes a value in the range 1 through 4094 for MSTI as
defined in [802.1q] Section 12.8.1.2.2 and takes value of 0 for
CIST.
3.3.5. STP Configuration Digest
This TLV carries the value of STP VLAN Instance Mapping.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA7 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Configuration Digest |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA7 for "STP Configuration Digest"
- Length
Length of the STP Configuration Digest. Always set to 16
octets.
- Configuration Digest
As specified in [802.1q] Section 13.8 bullet d)).
3.4. STP State TLVs
The STP State TLVs are sent in the RG Application Data message. They
are used by a PE device to report its STP status to other members in
the RG. Such TLVs are specified in the following subsections.
3.4.1. STP Topology Changed Instances
This TLV is used to report the Topology Changed Instances to other
members of the RG. The sender monitors TCN messages and generates
this list. The receiving RG member MUST initiate the Topology Change
event, including sending BPDU with the Topology Change flag set to 1
out of the designated port(s) of the Topology Changed bridge domains
of the STP network, flushing out of MAC addresses relevant to the
instances listed in this TLV.
If the PE device supports MAC Address Withdrawal (see Section 6.2 of
[RFC4762]), it SHOULD send an Label Distribution Protocol (LDP)
Address Withdraw Message with the list of MAC addresses towards the
core over the corresponding LDP sessions. It is not necessary to send
such a message to PEs of the same RG since the flushing of their MAC
address tables should have been performed upon the receipt of "STP
Topology Changed Instances" TLV.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA8 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| InstanceID List |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA8 for "STP Topology Changed Instances"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields.
- InstanceID List
The list of the InstanceIDs of CIST or MSTIs whose topologies
have changed as indicated by the Topology Change Notification
(TCN) Messages as specified in [802.1q] Section 13.14. The list
is formatted by padding Instance ID value to 16 bit boundary as
follows, where the bits in the "R" fields MUST be sent as zero
and ignored on receipt.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|R|R|R| InstanceID#1 |R|R|R|R| InstanceID#2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.4.2. STP CIST Root Time Parameters
This TLV is used to report the Value of CIST Root Time Parameters
([802.1q] Section 13.26.7) to other members of the RG. All time
parameter values are in seconds with a granularity of 1. For ranges
and default values of these parameter values, refer to [802.1d1998]
Section 8.10.2 Table 8-3, [802.1d2004] Section 17.14 Table 17-1, and
[802.1q] Section 13.26.7.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA9 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MaxAge | MessageAge |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FwdDelay | HelloTime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RemainingHops |
+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA9 for "STP CIST Root Time"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields. Always set to 9.
- MaxAge
The Max Age of the CIST. It is the maximum age of the
information transmitted by the bridge when it is the Root Bridge
([802.1d2004] Section 17.13.8).
- MessageAge
The Message Age of the CIST (see [802.1q] Section 13.26.7).
- FwdDelay
The Forward Delay of the CIST. It is the delay used by STP
Bridges to transition Root and Designated Ports to Forwarding
([802.1d2004] Section 17.13.5).
- HelloTime
The Hello Time of the CIST. It is the interval between periodic
transmissions of Configuration Messages by Designated Ports
([802.1d2004] Section 17.13.6).
- RemainingHops
The remainingHops of the CIST ([802.1q] Section 13.26.7) .
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3.4.3. STP MSTI Root Time Parameter
This TLV is used to report the parameter value of MSTI Root Time to
other members of the RG. As defined in [802.1q] Section 13.26.7, it
is the value of remainingHops for the given MSTI.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA10 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pri | InstanceID | RemainingHops |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA10 for "STP MSTI Root Time"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields. Always set to 3.
- Pri
The Instance Priority. It is interpreted as an unsigned integer
with higher value indicating a higher priority.
- InstanceID
The 12 bits Instance IDentifier of the Multiple Spanning Tree
Instance (MSTID). As defined in [802.1q] Section 12.8.1.2.2,
this parameter takes a value in the range 1 through 4094.
- RemainingHops
The remainingHops of the MSTI. It is encoded in the same way as
in [802.1q] Section 14.4.1 bullet f).
3.5. STP Synchronization Request TLV
The STP Synchronization Request TLV is used in the RG Application
Data message. This TLV is used by a device to request from its peer
to re-transmit configuration or operational state. The following
information can be requested:
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- configuration and/or state of the STP system,
- configuration and/or state for a given list of instances.
The format of the TLV is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA11 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request Number |C|S| Request Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| InstanceID List |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA11 for "STP Synchronization Request TLV"
- Length
Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields. Always set to 4.
- Request Number
2 octets. Unsigned integer uniquely identifying the request.
Used to match the request with a corresponding response. The
value of 0 is reserved for unsolicited synchronization, and MUST
NOT be used in the STP Synchronization Request TLV. As indicated
in [RFC7275], given the use of TCP, there are no issues
associated with the wrap-around of the Request Number.
- C-bit
Set to 1 if the request is for configuration data. Otherwise,
set to 0.
- S-bit
Set to 1 if the request is for running state data. Otherwise,
set to 0.
- Request Type
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14-bits specifying the request type, encoded as follows:
0x00 Request System Data
0x01 Request data of the listed instances
0x3FFF Request System Data and data of all instances
- InstanceID List
The InstanceIDs of CIST or MSTIs, format specified in Section
3.4.1.
3.6. STP Synchronization Data TLV
The pair of STP Synchronization Data TLVs are used by sender to
delimit a set of TLVs that are being transmitted in response to an
STP Synchronization Request TLV. The delimiting TLVs signal the start
and end of the synchronization data, and associate the response with
its corresponding request via the 'Request Number' field. It's
REQUIRED that each pair of STP Synchronization Data TLVs occur in the
same fragment. When the total size of the TLVs to be transmitted
exceeds the maximal size of a fragment, these TLVs MUST be divided
into multiple sets, delimited by multiple pairs of STP
Synchronization Data TLVs, and filled into multiple fragments. With
the Request Number lost fragments can be identified and re-
requested.
The STP Synchronization Data TLVs are also used for unsolicited
advertisements of complete STP configuration and operational state
data. The 'Request Number' field MUST be set to 0 in this case.
STP Synchronization Data TLV has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=TBA12 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request Number | Reserved |S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
set to TBA12 for "STP Synchronization Data TLV"
- Length
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Length of the TLV in octets excluding the U-bit, F-bit, Type,
and Length fields. Always set to 4.
- Request Number
2 octets. Unsigned integer identifying the Request Number of the
"STP Synchronization Request TLV" which initiated this
synchronization data response.
- Reserved
Reserved bits for future use. These MUST be sent as zero and
ignored on receipt.
-S
S = 0: Synchronization Data Start
S = 1: Synchronization Data End
4. Operations
Operational procedures for AC redundancy applications have been
specified in Section 9.2 of [RFC7275]. The operational procedures of
ICCP STP application should follow these procedures except the
changes presented in this section.
4.1. Common AC Procedures
For the generic procedures of AC redundancy applications defined in
Section 9.2.1 of [RFC7275], the following changes are introduced.
4.1.1. Remote PE Node Failure or Isolation
When a local PE device detects that a remote PE device that is a
member of the same RG is no longer reachable (using the mechanisms
described in Section 5 of [RFC7275]), the local PE device checks if
it has redundancy ACs for the affected services. In case of redundant
ACs present, and if the local PE device has the new highest bridge
priority, the local PE device becomes the virtual root bridge for
corresponding ACs.
4.1.2. Local PE Isolation
When a PE device detects that it has been isolated from the core
network, then it need ensure that its AC redundancy mechanism will
change the status of all active ACs to standby. The AC redundancy
application SHOULD then send ICCP "Application Data" message in order
to trigger failover to another active PE device in the RG. Note that
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this works only in the case of dedicated interconnect (Sections 3.2.1
and 3.2.3), since ICCP will still have the path to the peer, even
though the PE device is isolated from the MPLS core network.
4.2. ICCP STP Application Procedures
This section defines the procedures that are specific to the ICCP STP
application which are applicable for Ethernet ACs.
4.2.1. Initial Setup
When a RG is configured on a system that supports the ICCP STP
application, such systems MUST send an "RG Connect" message with "STP
Connect TLV" to each PE device that is member of the RG. The sending
PE device MUST set the A bit to 1 in that TLV if it has received a
corresponding "STP Connect TLV" from its peer PE; otherwise, the
sending PE device MUST set the A bit to 0. If a PE device receives an
"STP Connect TLV" from its peer after sending its own TLV with the A
bit set to 0, it MUST resend the TLV with the A bit set to 1. A
system considers the ICCP STP application connection to be
operational when it has both sent and received "STP Connect TLVs"
with the A bit set to 1. When the ICCP STP application connection
between a pair of PEs is operational, the two devices can start
exchanging "RG Application Data" messages for the ICCP STP
application. This involves having each PE device advertise its STP
configuration and operational state in an unsolicited manner. A PE
device SHOULD follow the following order when advertising its STP
state upon initial application connection setup:
- Advertise system configuration TLV
- Advertise remaining configuration TLVs
- Advertise state TLVs
The update of the information contained in the State TLVs depends on
that in the configuration TLVs. By sending the TLVs in the above
order, the two peers may begin to update STP state as early as
possible in the middle of exchanging these TLVs.
A PE device MUST use a pair of "STP Synchronization Data TLVs" to
delimit the entire set of TLVs that are being sent as part of this
unsolicited advertisement.
If a system receives an "RG Connect" message with "STP Connect TLV"
that has a differing Protocol Version, it MUST follow the procedures
outlined in the "Application Versioning" Section of [RFC7275].
After the ICCP STP application connection has been established, every
PE device MUST communicate its system level configuration to its
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peers via the use of "STP System Config TLV".
When the ICCP STP application is administratively disabled on the PE,
or on the particular RG, the system MUST send an "RG Disconnect"
message containing "STP Disconnect TLV".
4.2.2. Configuration Synchronization
A system that supports ICCP STP application MUST synchronize the
configuration with other RG members. This is achieved via the use of
"STP Config TLVs". The PEs in the RG MUST all agree on the common MAC
address to be associated with the virtual root bridge. It is possible
to achieve this via consistent configuration on member PEs. However,
in order to protect against possible misconfigurations, a virtual
root bridge identifier MUST be set to the MAC address advertised by
the PE device with the numerically lowest BridgeIdentifier (i.e., the
MAC address of the bridge) in the RG.
Furthermore, for a given ICCP STP application, an implementation MUST
advertise the configuration prior to advertising its corresponding
state. If a PE device receives any STP State TLV that it had not
learned of before via an appropriate STP Config TLV, then the PE
device MUST request synchronization of the configuration and state
from its peer. If during such synchronization a PE device receives a
State TLV that it has not learned before, then the PE device MUST
send a NAK TLV for that particular TLV. The PE device MUST NOT
request resynchronization in this case.
4.2.3. State Synchronization
PEs within the RG need to synchronize their state for proper STP
operation. This is achieved by having each system advertise its
running state in STP State TLVs. Whenever any STP parameter either on
the CE or PE side is changed, the system MUST transmit an updated TLV
for the affected STP instances. Moreover, when the administrative or
operational state changes, the system MUST transmit an updated state
TLV to its peers.
A PE device MAY request its peer to retransmit previously advertised
state. This is useful in case of the PE device recovering from a soft
failure and attempting to relearn state. To request such
retransmissions, a PE device MUST send a set of one or more "STP
Synchronization Request TLVs".
A PE device MUST respond to a "STP Synchronization Request TLV" by
sending the requested data in a set of one or more STP configuration
or state TLVs delimited by a pair of "STP Synchronization Data
TLVs".
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Note that the response may span across multiple RG Application Data
messages, for example when MTU limits are exceeded; however, the
above ordering MUST be retained across messages, and only a single
pair of Synchronization Data TLVs MUST be used to delimit the
response across all Application Data Messages.
A PE device MAY readvertise its STP state in an unsolicited manner.
This is done by sending the appropriate State TLVs delimited by a
pair of "STP Synchronization Data TLVs" and using a 'Request Number'
of 0.
While a PE device has sent out a synchronization request for a
particular PE device, it SHOULD silently ignore all TLVs from that
node, that are received prior to the synchronization response and
which carry the same type of information being requested. This saves
the system from the burden of updating state that will ultimately be
overwritten by the synchronization response. Note that TLVs
pertaining to other systems should continue to be processed normally.
If a PE device receives a synchronization request for an instance
that doesn't exist or is not known to the PE, then it MUST trigger
the unsolicited synchronization of all information by restarting the
initialization.
If during the synchronization operation a PE device receives an
advertisement of a Node ID value which is different from the value
previously advertised, then the PE device MUST purge all state data
previously received from that peer prior to the last synchronization.
4.2.4. Failure and Recovery
When a PE device that is active for the ICCP STP application
encounters a core isolation fault [RFC7275], it SHOULD attempt to
fail-over to a peer PE device which hosts the same RG. The default
fail-over procedure is to have the failed PE device bring down the
link(s) towards the multi-homed STP network. This will cause the STP
network to reconverge and to use the other links that are connected
to the other PE devices in the RG. Other procedures for triggering
fail-over are possible, and are outside the scope of this document.
If the isolated PE device is the one that has the numerically lowest
BridgeIdentifier, PEs in the RG MUST synchronize STP configuration
and state TLVs and determine a new virtual root bridge as specified
in Section 4.2.2.
Upon recovery from a previous fault, a PE device SHOULD NOT reclaim
the role of the virtual root for the STP network even if it has the
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numerically lowest BridgeIdentifier among the RG. This minimizes
traffic disruption.
Whenever the virtual root bridge changes, the STP Topology Changed
Instances TLV lists the instances that are affected by the change.
These instances MUST undergo a STP reconvergence procedure when this
TLV is received as defined in Section 3.4.1.
5. Security Considerations
This document specifies an application running on the channel
provided by ICCP [RFC7275]. The security considerations on ICCP apply
in this document as well.
For the ICCP STP application, an attack on a channel (running in the
provider's network) can break not only the ability to deliver traffic
across the provider's network, but also the ability to route traffic
within the customer's network. That is, a careful attack on a channel
(such as the DOS attacks as described in [RFC7275]) can break STP
within the customer network. Implementations need provide mechanisms
to mitigate these types of attacks. For example, the port between the
PE device and the malicious CE device may be blocked.
6. IANA Considerations
The IANA maintains a top-level registry called "Pseudowire Name
Spaces (PWE3)". It has a sub-registry called "ICC RG Parameter
Types".
IANA is requested to make 13 allocations from this registry as shown
below. IANA is requested to allocate the codepoints in sequential
block starting from the next available value in the range marked for
assignment by IETF review (0x2000-0x2FFF) [RFC5226]. All assignments
should reference this document.
Parameter Type Description
-------------- ---------------------------------
TBA1 STP Connect TLV
TBA2 STP Disconnect TLV
TBA3 STP System Config TLV
TBA4 STP Region Name TLV
TBA5 STP Revision Level TLV
TBA6 STP Instance Priority TLV
TBA7 STP Configuration Digest TLV
TBA8 STP Topology Changed Instances TLV
TBA9 STP STP CIST Root Time TLV
TBA10 STP MSTI Root Time TLV
TBA11 STP Synchronization Request TLV
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TBA12 STP Synchronization Data TLV
TBA13 STP Disconnect Cause TLV
Acknowledgements
Authors would like to thank the comments and suggestions from Ignas
Bagdonas, Adrian Farrel, Andrew G. Malis, Gregory Mirsky and
Alexander Vainshtein.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
[RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Signaling", RFC 4762, January 2007.
[RFC7275] Martini, L., Salam, S., Sajassi, A., Bocci, M., Matsushima,
S., and T. Nadeau, "Inter-Chassis Communication Protocol for
Layer 2 Virtual Private Network (L2VPN) Provider Edge (PE)
Redundancy", RFC 7275, June 2014.
[802.1q] "IEEE Standard for Local and Metropolitan Area Networks---
Virtual Bridged Local Area Networks". IEEE Std 802.1 Q-2014,
November 11, 2014.
[802.1d1998] "Information technology---Telecommunications and
information exchange between systems---Local and metropolitan
area networks---Common specifications--Part 3: Media Access
Control (MAC) Bridges". ANSI/IEEE Std 802.1D, 1998 Edition.
[802.1d2004] "IEEE Standard for Local and metropolitan area networks-
-- Media Access Control (MAC) Bridges". IEEE Std 802.1 D-2004.
7.2. Informative References
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
2008.
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Author's Addresses
Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd. Haidian District,
Beijing 100095
P.R. China
EMail: zhangmingui@huawei.com
Huafeng Wen
Huawei Technologies
101 Software Avenue,
Nanjing 210012
P.R. China
EMail: wenhuafeng@huawei.com
Jie Hu
China Telecom
EMail: hujie@ctbri.com.cn
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