Internet Working Group Y. Jiang
Y. Luo
Internet Draft Huawei
Intended status: Standards Track
Expires: April 2014 October 21, 2013
Multi-chassis PON Protection in MPLS
draft-jiang-pwe3-mc-pon-00.txt
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Abstract
While MPLS is deployed further and further to the access network, a
converging network edge point which provides both MPLS and PON access
capability appears. To provide resiliency for its services, multi-
homing is needed to support PON access in MPLS. This document
describes the multi-chassis PON protection architecture in MPLS and
also proposes the ICCP extension to support it.
Table of Contents
1. Conventions used in this document ......................... 2
2. Terminology ............................................... 3
3. Introduction .............................................. 3
3.1. Multi-chassis PON Application TLVs ..................... 5
3.1.1. PON Connect TLV ..................................... 5
3.1.2. PON Disconnect TLV .................................. 6
3.1.3. PON Configuration TLV ............................... 6
3.1.4. PON State TLV ....................................... 7
4. Dual Homing protection procedures ......................... 8
4.1. Protection procedure upon PON interface failures ....... 9
4.2. Protection procedure upon PW failures .................. 9
4.3. Protection procedure upon the working OLT failure ...... 9
5. Security Considerations .................................. 10
6. IANA Considerations ...................................... 10
7. References ............................................... 10
7.1. Normative References .................................. 10
7.2. Informative References ................................ 10
8. Acknowledgments .......................................... 10
Authors' Addresses ............................................ 11
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 [RFC2119].
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2. Terminology
FTTx Fiber-to-the-x (FTTx, x = H for home, P for premises, C for curb)
ICCP Inter-Chassis Communication Protocol
OLT Optical Line Termination
ONU Optical Network Unit
MPLS Multi-Protocol Label Switching
PON Passive Optical Network
3. Introduction
MPLS is extending further and further to the edge of networks, for
example, the seamless MPLS use cases as described in [SEAMLESS], and
the MS-PW with PON access use case as described in [RFC6456], all
show that MPLS is approaching the access networks.
Passive Optical Network (PON) can provide high bandwidth of 1Gbps or
even 10Gbps, and provide support of access for dozens to more than
one hundred subscribers at the same time. A huge number of PON access
networks have been deployed over the last few years with the wide
spread of FTTx technology.
With the fast growth of mobile data traffic, more and more LTE small
cells and Wi-Fi hotspots will be deployed in the future. How to
backhaul a large number of small cells or hotspots will pose a great
challenge to mobile service providers.
PON access technology has the following advantages:
-saving trunk fibers with its point-to-multipoint physical topology;
-High bandwidth capability up to 10Gbps;
-Low Total Cost of Ownership (TCO).
PON also provides synchronization features, e.g., SyncE and IEEE1588
functionality, which can fulfill synchronization needs of mobile
backhaul services. Some optical layer of protection mechanisms, such
as Type B protection and Type C protection are also specified [G983.1]
to avoid single point of failure in the access.
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Therefore, PON may play a greater role in the access end for the
mobile backhaul networks. Providing OLTs with MPLS functionality
further facilitates multi-service convergence.
Type B protection architecture is an economical PON resiliency
mechanism, where the working OLT and the working link between the
working splitter and the working OLT (i.e., the working fiber) is
protected by a redundant protection OLT and a redundant fiber between
the working splitter and the protection OLT. This is different from
the more complex and costly Type C protection architecture where
working splitter and the working fibers from ONUs to the working
splitter are further protected. Figure 1 demonstrates a typical
scenario of Type B PON protection.
| |
|<--Optical Distribution Network->|
| |
| branch trunk +-----+
+-----+ fibers fibers | |
Base ------| | | . OLT |
Stations ------| ONU |\ | ,'`| A |
------| | \ V _-` +-----+
+-----+ \ .'
. \ +----------+ ,-`
+-----+ . \| -` Working
Base ------| | . | Optical |
Stations ------| ONU |---------| Splitter |
------| | . /| -, Protection
+-----+ . / +----------+ `'.,
/ `-, +-----+
+-----+ / `'.,| |
Base ------| |/ | OLT |
Stations ------| ONU | | B |
------| | +-----+
+-----+
Figure 1 Type B PON protection Architecture
Though the above PON architecture provides redundancy in its physical
topology, some standard mechanisms are needed to exchange PON link
status and network status between OLTs in a Redundancy Group (RG) so
that protection and restoration can be done reliably, especially when
the OLTs also support MPLS. Thus there is a need for Multi-chassis
PON protection protocol in MPLS.
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ICCP [ICCP] provides a framework for inter-chassis synchronization of
state and configuration data between a set of two or more PEs.
Currently ICCP only defines application specific messages for PW
redundancy and mLACP, but it can be easily extended to support Type B
PON as an Attachment Circuit (AC) redundancy.
This document proposes the extension of ICCP to support Multi-chassis
PON protection in MPLS.
3.1. Multi-chassis PON Application TLVs
A set of multi-chassis PON application TLVs are defined in the
following sub-sections.
3.1.1. PON Connect TLV
This TLV is included in the RG Connect message to signal the
establishment of PON 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=0x00XX | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol Version |A| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Sub-TLVs |
~ ~
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U and F Bits, both are set to 0.
- Type, set to 0x00XX for "PON Connect TLV".
- Length, Length of the TLV in octets excluding the U-bit, F-bit,
Type, and Length fields.
- Protocol Version, the version of this PON specific protocol for the
purposes of inter-chassis communication. This is set to 0x0001.
- A Bit, Acknowledgement Bit. Set to 1 if the sender has received a
PON Connect TLV from the recipient. Otherwise, set to 0.
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- Reserved, Reserved for future use.
- Optional Sub-TLVs, there are no optional Sub-TLVs defined for this
version of the protocol.
3.1.2. PON Disconnect TLV
This TLV is included in the RG Disconnect message to indicate that
the connection for the PON 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=0x00XX | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U and F Bits, both are set to 0.
- Type, set to 0x00XX for "PON Disconnect TLV".
- Length, Length of the TLV in octets excluding the U-bit, F-bit,
Type, and Length fields.
- Optional Sub-TLVs, there are no optional Sub-TLVs defined for this
version of the protocol.
3.1.3. PON Configuration 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=0x00XX | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| System ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | System Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U and F Bits, both are set to 0.
- Type, set to 0x00XX for "PON Configuration TLV".
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- Length, Length of the TLV in octets excluding the U-bit, F-bit,
Type, and Length fields.
- System ID, 6 octets encoding the System ID used by the OLT, which
is a MAC address.
- System Priority, 2 octets encoding the System Priority.
- Port ID, 2 octets PON Port ID.
Further configuration considerations such as multicast table and ARP
table for static MAC addresses will be added in a next version.
3.1.4.PON State 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type=0x00XX | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ROID |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local PON Port state |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote PON Port state |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U and F Bits, both are set to 0.
- Type, set to 0x00XX for "PON State TLV"
- Length, Length of the TLV in octets excluding the U-bit, F-bit,
Type, and Length fields.
- ROID, as defined in the ROID section of [ICCP].
- Local PON Port State, the status of the local PON port as
determined by the sending OLT (PE). The last bit is defined as Fault
indication of the PON Port associated with this PW.
- Remote PON Port State, the status of the remote PON port as
determined by the remote peer of the sending OLT (PE). The last bit
is defined as Fault indication of the PON Port associated with this
PW.
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4. Dual Homing protection procedures
Two typical MPLS protection network architectures for PON access are
depicted in Fig.2 and Fig.3 (PON access segment is the same as in
Fig.1 and thus omitted for simplification). OLTs with MPLS
functionality are connected to a single PE (Fig.2) or dual home PEs
(Fig.3) respectively, thus these devices constitute an MPLS network
which provides PW transport services between ONUs and a CE.
+-----+
| |
| OLT -,
| | `.,
+-----+ ',
`',
`., +-----+ +-----+
', | | | |
`. PE ------------ CE |
.'`| | | |
,-` +-----+ +-----+
.`
+-----+ .'`
| | ,-`
| OLT -`
| |
+-----+
Figure 2 An MPLS network with a single PE
+-----+ +-----+
| | | |
| OLT ----------------- PE -,
| | | | ',
+-----+ +--/--+ ',
| `.
| `. +-----+
| `' |
| | CE |
| . |
| ,'+-----+
| ,-`
+-----+ +--\--+ ,'
| | | | .`
| OLT ----------------- PE -`
| | | |
+-----+ +-----+
Figure 3 An MPLS network with dual home PEs
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Faults may be encountered in PON access, or in the MPLS network
(including the working OLT). Procedures for these cases are described
in this section (it is assumed that both OLTs and PEs are working in
independent mode of PW redundancy [RFC6870]).
4.1. Protection procedure upon PON interface failures
When a fault is detected on a working PON link, a working OLT MUST
turn off its associated PON interface and MUST send an LDP
notification message with a forward defect indication and with the
Request Switchover bit being set to its peer PE on the remote end of
the PW. At the same time, the working OLT MUST send an ICCP message
with PON State TLV to notify the backup OLT of the PON fault.
Upon receiving a PON state TLV where Local PON Port state is False,
an OLT in the protection mode MUST activate the protection PON link
in the protection group.
4.2. Protection procedure upon PW failures
Usually MPLS networks have its own protection mechanism such as LSP
protection or Fast Reroute (FRR). But in a link sparse access or
aggregation network where protection is impossible in LSP layer, the
following PW layer protection procedures can be enabled.
When a fault is detected on its working PW (e.g., by VCCV BFD), a
working OLT MUST turn off its associated PON interface and MUST send
an ICCP message with PON State TLV to notify the backup OLT of the
PON fault.
Upon receiving a PON state TLV where Local PON Port state is False,
the backup OLT MUST activate its optical interface to the backup
fiber. At the same time, the backup OLT MUST send a PW redundancy
message to the remote PE, so that traffic can be switched to the
backup PW.
4.3. Protection procedure upon the working OLT failure
If the backup OLT lost connection to the working OLT, it MUST
activate its optical interface to the back fiber and activate the
specific backup PW upon receiving a PW redundancy message from its
remote PE with the Request Switchover bit being set, so that traffic
can be reliably switched to the protection link and the backup PW.
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5. Security Considerations
Security considerations as described in [ICCP] apply.
6. IANA Considerations
These values are requested from the registry of "ICC RG parameter
type":
0x00X0 PON Connect TLV
0x00X1 PON Disconnect TLV
0x00X2 PON Configuration TLV
0x00X3 PON State TLV
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
[RFC6870] Muley, P., Aissaoui, M., "Pseudowire Preferential
Forwarding Status Bit", RFC 6870, February 2013
7.2. Informative References
[RFC6456] Li, H., Zheng, R., and Farrel, A., "Multi-Segment
Pseudowires in Passive Optical Networks", RFC 6456,
November 2011
[SEAMLESS] Leymann, N., and et al, "Seamless MPLS Architecture",
draft-ietf-mpls-seamless-mpls-04, Work in progress
[ICCP] Martini, L. and et al, "Inter-Chassis Communication Protocol
for L2VPN PE Redundancy", draft-ietf-pwe3-iccp-11, Work in
progress
[G983.1] ITU-T, "Broadband optical access systems based on Passive
Optical Networks (PON)", ITU-T G.983.1, January, 2005
8. Acknowledgments
TBD.
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Authors' Addresses
Yuanlong Jiang
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129, China
Email: jiangyuanlong@huawei.com
Yong Luo
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129, China
Email: dennis.luoyong@huawei.com
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