Network Working Group H. Long
Internet Draft M. Ye
Intended status: Standards Track Huawei Technologies Co., Ltd.
Expires: August 2013 February 18, 2013
Multi-Segment Pseudowire Signaling with Availability Information
draft-long-pwe3-ms-pw-availability-01.txt
Abstract
This document describes a signaling mechanism for setting up a
multi-segment pseudowire between different domains in case that at
least one domain has the feature that bandwidth capacity is variable
for different availability values. The signaling mechanism is an
extension on the multi-segment pseudowire signaling [DYN-MS-PW].
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document authors. All rights reserved.
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Table of Contents
1. Introduction ................................................ 2
2. LDP Signaling ............................................... 3
3. Security Considerations...................................... 4
4. IANA Considerations ......................................... 4
5. References .................................................. 4
5.1. Normative References.................................... 4
5.2. Informative References.................................. 4
6. Acknowledgments ............................................. 5
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. Introduction
[RFC5659] describes the architecture of multi-segment pseudowire.
The LDP signaling mechanism for setting up multi-segement pseudowire
is described by [DYN-MS-PW]. The mechanism introduces a pseudowire
bandwidth TLV for PSN tunnel selection.
In some networks, there may be some links with variable bandwidth.
For example, in mobile backhaul network, microwave links are very
popular for providing connection of last hops. In case of heavy rain,
to maintain the link connectivity, the microwave link will lower the
modulation format since demodulating lower modulation format need
lower signal-to-noise ratio (SNR). This is called adaptive
modulation technology. However, lower modulation format also means
lower link bandwidth. Similarly the cooper links may change their
link bandwidth due to external interference.
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The parameter, availability [G.827, F.1703], is often used to
describe the link capacity during network planning. A link may
provide different bandwidth for different availability requirement
In this case, a LSP across the links should include multiple
bandwidth portions with different availability guarantee. As a
result, only PW bandwidth requirement information is not enough for
the multi-segment pseudowire setup.
An optional PW availability TLV is introduced in this document for
providing enough information for S-PE to selecting PSN tunnel.
2. LDP Signaling
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| Availability TLV(TBD) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Availability requirement |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 - PW Availability TLV
The optional PW availability TLV described by Figure 1 includes an
availability requirement field which is a 32-bit floating point
number. This field describes the availability requirement for the
multi-segment pseudowire. The value can be inherited from the
availability requirement of the emulated service. It should be
smaller than 1.
When an S/T-PE receives a PW availability TLV and a PW bandwidth TLV,
it will search for an PSN tunnel which can satisfy the bandwidth
requirement with the availability requirement. Once the PW next hop
is selected, the S/T-PE MUST request the appropriate resources which
can guarantee the required availability from the PSN.
In the case where PSN resources towards the next hop cannot satisfy
the bandwidth request with the specified the availability
requirement; the following procedure MUST be followed:
-i. The PSN MAY allocate more QoS resources, e.g. Bandwidth with
required availability guranttee, to the PSN tunnel.
-ii. The S-PE MAY attempt to setup another PSN tunnel to
accommodate the new PW QoS requirements.
-iii. If the S-PE cannot get enough resources to setup the
segment in the MS-PW a label release MUST be returned to the
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previous hop with a status message of "Bandwidth resources
unavailable"
In the latter case, the T-PE receiving the status message MUST also
withdraw the corresponding PW label mapping for the opposite
direction if it has already been successfully setup.
3. Security Considerations
This document does not introduce new security considerations.
4. IANA Considerations
TBD.
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5659] Bocci, M., Bryant, S., "An Architecture for Multi-Segment
Pseudowire Emulation Edge-to-Edge", RFC 5659, October 2009.
[DYN-MS-PW] Martini, L., Bocci, M., Balus, F., "Dynamic Placement of
Multi Segment Pseudo Wires", draft-ietf-pwe3-dynamic-ms-
pw-16, October, 2010
[G.827] ITU-T Recommendation, "Availability performance parameters
and objectives for end-to-end international constant bit-
rate digital paths", September, 2003.
[F.1703] ITU-R Recommendation, "Availability objectives for real
digital fixed wireless links used in 27 500 km
hypothetical reference paths and connections", January,
2005.
5.2. Informative References
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6. Acknowledgments
Authors' Addresses
Hao Long
Huawei Technologies Co., Ltd.
No.1899,Xiyuan Avenue, Hi-tech Western District
Chengdu 611731, P.R.China
Email: longhao@huawei.com
Min Ye
Huawei Technologies Co., Ltd.
No.1899,Xiyuan Avenue, Hi-tech Western District
Chengdu 611731, P.R.China
Email: amy.yemin@huawei.com
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