OPSAWG WG M. Georgiades
Internet-Draft PrimeTel
Intended Status: Informational F.Cugini
Expires: 24 November 2011 CNIT
D. Berechya
NSN
O. Gonzalez
TID
May 24, 2011
Inter-Carrier OAM Requirements
draft-georgiades-opsawg-intercar-oam-req-00.txt
Abstract
This draft considers inter-carrier OAM requirements for supporting
end-to-end OAM functionality and mechanisms development in a multi-
operator environment. It attempts to summarize and discuss the
already proposed OAM requirements addressed in IETF [RFC5706,
RFC5860], ITU-T [Y.1710, Y.1730], MEF [MEFOAM] and IEEE [IEEE1,
IEEE2] which were mainly proposed on a per transport technology
basis, and introduce the need for a distinction and additional
requirements for the inter-carrier OAM operations.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright and License Notice
Copyright (c) 2011 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
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Inter-carrier OAM Requirements . . . . . . . . . . . . . . . . 5
3.1. OAM single region/single carrier transport network
requirements . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. OAM for inter-carrier transport networks . . . . . . . . . 9
4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1 Introduction
OAM functionality is important in network operation for ease of
monitoring including fault notification and isolation, for verifying
network performance, and to reduce operational costs. To pursue end-
to-end services delivery crossing domains that are heterogeneous in
terms of technologies (circuit transport networks and connection-
oriented packet transport networks) as well as accommodate for the
different commercial administration/operation policies of carriers,
the distinction of inter-carrier OAM requirements (as opposed to OAM
requirements per technology) must be addressed.
OAM operations have been considered for different data transport
technologies by different standardization bodies. Some solution
examples include ATM OAM ITU-T I.610 [I.610], IEEE 802.3-2008
[IEEE1], ITU-T Y.1730 [Y.1730], ITU-T Y.1710 [Y.1710], IETF RFC 5706
[RFC5706], IETF RFC 5860 [RFC5860]. These protocols have been
designed by different working groups to handle three main functions
namely: (A) Failure Detection and Diagnostics, (B) Recovery, and (C)
Performance Monitoring for a particular technology including SONET &
SDH, ATM, MPLS and Carrier Ethernet. Inter-operability considerations
between different OAM mechanisms proposed for the different transport
technologies have been left for future studies. Although some of the
proposed OAM protocols do mention interoperability considerations,
requirement details and solutions for these are usually out of the
scope. Moreover considering common syntax among protocols to resolve
interoperability issues has proven difficult.
OAM functions have been proposed mainly for fault management but also
performance monitoring. [Y.1731] lists the following functions for
Ethernet fault management: Continuity Check, Loopback, Link Trace,
Alarm Indication Signal, Remote Defect Indication, Locked Signal,
Test Signal, Automatic Protection Switching, Maintenance
Communication Channel, Experimental OAM and Vendor Specific OAM. For
Ethernet performance monitoring [Y.1731] lists the following
necessary functions: loss measurement, delay measurement and
throughput measurement.
A similar approach was followed for the development of other OAM
mechanism mainly on a per technology basis. Inter-operability and
inter-carrier issues have not been addressed thoroughly.
1.1 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 RFC 2119 [RFC2119].
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OAM
Operation, Administration and Maintenance Maintenance Entity (ME)
It represents an entity that requires management.
MEG
Maintenance Entity Group (MEG) consists of the MEs that belong to
the same service inside a common OAM domain. For a Point-to-Point
EVC, a MEG contains a single ME. For a Multipoint-to-Multipoint
EVC of n UNIs, a MEG contains n*(n-1)/2 MEs.
OAM transparency
This term refers to the ability to allow transparent carrying of
OAM packets belonging to higher level MEGs across other lower
level MEGs when the MEGs are nested.
In-service OAM
It refers to OAM actions which are carried out while the data
traffic is not interrupted with an expectation that data traffic
remains transparent to OAM actions.
On-demand OAM
It refers to OAM actions which are initiated via manual
intervention for a limited time to carry out diagnostics.
Proactive OAM
It refers to OAM actions which are carried out continuously to
permit proactive reporting of fault and/or performance results.
In-Service OAM
It refers to OAM actions which are carried out during data
delivery e.g. for monitoring performance.
Out-of-service OAM
It refers to OAM actions which are carried out while the data
traffic is interrupted.
On-path service NSP
A transit NSP who is used as a traffic carrier or service provider
of a particular service.
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Service-based OAM
Service Level OAM relates to any operations which are associated
with a particular service. A good example is the delivery of the
agreed throughput (service issue) as opposed to allocated
bandwidth for the link/segment (network resource issue).
Network-based OAM
Network-based OAM relates to any operations which are associated
with a particular network links, network segments, network
resources etc. A good example is the delivery of the agreed
bandwidth on a network segment (network resource issue) as opposed
to the actual throughput delivered (service issue).
Carrier
A carrier is an organization that provides communications and
networking services; Also referred to as a Network Service
Provider (NSP) in the draft.
Region
A region is considered to be a collection of network elements
under a single technology.
Domain
A domain is considered to be any collection of network elements
within a common sphere of address management or path computational
responsibility. Examples of such domains include IGP areas and
Autonomous Systems;
2. Inter-carrier OAM Requirements
Requirements for Operational, Administration and Maintenance have
already been defined in detail by ITU-T, IETF and MEF, regarding the
single-domain scenario.
OAM Requirements considered so far depend mainly on the data
transport network technology they aim to support. Y.1710 for example
has defined OAM requirements for OAM functionality for MPLS networks.
Similarly Y.1730 defined requirements for OAM functions in Ethernet-
based networks.
Different OAM protocols have been recommended and used for different
data transport technologies. Also different Networks Service
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Providers (NSPs) may chose to use different OAM models to monitor
their operation, maintenance and fault detection, checking network
devices possibly from different vendors, different models and
different releases. This gives rise to several considerations when
dealing with interconnected heterogeneous networks and inter-NSP
scenarios particularly in cases where the end-to-end OAM control
information is of interest.
Current OAM functionalities do not guarantee interoperability among
different transport technologies and certain technologies (e.g.
Ethernet transport) are not sufficient to adequately support advanced
end-to-end services in inter-carrier scenarios.
This draft aims to emphasize on end-to-end inter-carrier OAM
requirements and the need to consider a twofold set of requirements
derived both from technological aspects but also technical
requirements derived from inter-carrier business considerations.
More specifically OAM inter-carrier requirements will need to
consider interoperability issues among different transport
technologies such as IP/MPLS, MPLS-TP, Ethernet, OTN etc. Inter-
technology OAM requirements and inter-operability requirements
between technologies has not been defined thoroughly within the
different standardization bodies (IETF, ITU-T, MEF, IEEE) which tend
to focus more on a per technology basis.
In addition, inter carrier networking involves, besides the
technological aspects, commercial aspects that by nature exist in any
cooperation between different business entities and are necessary for
inter-carrier operation, administration and management raise other
technical requirements. Furthermore some network events that are
detected and measured by end to end OAM such as failures may require
customer compensation and, in consequence, inter carrier
reimbursements. The current OAM system does not clearly provide
trusted means for determining the location and the duration of
failures in the environment of multi carrier where each carrier uses
different systems for measuring and logging the events.
To handle different possible scenarios for OAM it is important to
categorize the network scope that OAM support will be designed for.
The network scope may contain homogenous technological domains (or
regions), heterogeneous domains, and even different carriers (network
operators). Moreover it may be composed by elements belonging to
different technologies and having different switching capabilities.
The major data transport technologies are considered including Multi-
Protocol Label Switching - Transport Profile (MPLS-TP), Wavelength
Switched Optical Networks (WSON) and corresponding switching
capabilities like Packet Switching Capability (PSC) and Lambda
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Switching Capability (LSC) respectively.
|<-----------------Inter-Carrier OAM---------------->|
|<------------------Inter-Region OAM----------------->|
|<----------Inter-Carrier OAM--------->|
|<---Inter-Region OAM--->|
|<---Intra-Carrier OAM--->| |<--Intra-Carrier OAM--->|<-Intra-C.-->|
|<-IntraDom-><-IntraDom-->| |<-IntraDom-><-IntraDom->|<-IntraDom-->|
-------------------------- ------------------------ ------------
+---------+ +--------+ | | +--------+ +-----+ | | +-------+
| | | | | | | | | | | | | |
-| IP/MPLS |-- |IP/MPLS |-| | |MPLS-TP |--- | ETH |---- | OTN |--
| | | | | | | | | | | | | |
+---------+ +--------+ | | +--------+ +-----+ | | +-------+
Operator/Carrier 1 | | Operator/Carrier 2 | | Carrier 3
-------------------------- ------------------------ ------------
Figure 1 End-to-end OAM Operation Areas Definitions
Figure 1 shows how in a real end-to-end network scenarios, different
OAM areas of operation are depicted and the granularity level can be
summarized as follows:
i) Inter-Carrier OAM (between different network operators, same
or different technologies)
ii) Inter-Region OAM (between regions of different technologies,
same or different carriers)
iii) Intra-Carrier OAM (within a single carrier, between
homogenous or heterogeneous regions i.e. different technologies)
iv) Intra-Domain OAM (i.e. single technology, single domain)
Such identification of the OAM signaling range granularity proves
necessary for accommodating for single/multi-operator environment,
single/multi-regions or a combination of these. Intra-domain OAM e.g.
section or link OAM etc. are not in the scope of this draft.
It is worth noting that, until now, little attention has been paid to
the inter-region/inter-carrier cases and no clear distinction from
intra-region/intra-carrier requirements has been made by
standardization bodies.
Another important differentiation which is depicted in this draft and
it is of great importance particularly in inter-carrier operations is
Service Level OAM vs. Network Level OAM.
Service Level OAM relates to any operations which are associated with
a particular service. A good example will be the delivery of the
agreed throughput (service issue) as opposed to allocated bandwidth
for the link/segment (network resource issue). Network-based OAM
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relates to any operations which are associated with a particular
network links, network segments, network resources etc. A good
example will be the delivery of the agreed bandwidth on a network
segment (network resource issue) as opposed to the actual throughput
delivered (service issue).
3.1. OAM single region/single carrier transport network requirements
Both IETF and ITU-T have identified OAM requirements for a single
region transport network, for different technologies. In general the
requirements can be grouped under these two main categories:
architectural requirements and functional requirements. Most of the
single domain OAM requirements are relevant for the inter domain as
well. The most important architectural requirements are:
A. Independence of the OAM level from service and underlying
networks. In other terms, as reported in [RFC 5860] "The set of
OAM functions must be a self-sufficient set that does not require
external capabilities to achieve the OAM objectives"
B. Bidirectional application of OAM mechanisms should be possible.
C. Application of OAM functions to unidirectional point-to-point
and point-to-multipoint connections should be possible.
The functional requirements might be split into two further sub-
categories with regard to the task they are facing with: fault
detection and locating and performance monitoring. The main OAM
mechanisms required by the joint ITU-T - IETF working group for fault
management are:
A. Continuity check / verification
B. Alarm suppression C. Lock indication D. Diagnostic test E.
Trace-route F. Remote defect indication
The main OAM mechanisms required by the joint ITU-T - IEFT working
group for performance monitoring are:
A. Packet loss measurement
B. Delay and jitter measurement
On the other hand MEF, more focused on service OAM, has specified the
following list of requirements:
A. Service OAM should discover other elements in the Metro
Ethernet Networks (MEN)
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B. Service OAM should monitor the connectivity status of other
elements (active, not-active, partially active).
C. Performance monitoring should estimate Frame Loss Ratio (FLR)
Performance, Frame Delay Performance, and Frame Delay Variation
(FDV) Performance.
D. OAM frames should be prevented from "leaking" outside the
appropriate OAM domain to which they apply.
E. The OAM frames should traverse the same paths as the service
frames
F. The OAM should be independent of but allow interoperability
with the underlying transport layer and its OAM capabilities
G. The OAM should be independent of the application layer
technologies and OAM capabilities
3.2. OAM for inter-carrier transport networks
This subsection deals with inter-carrier and hence also inter-
region issues in the existing standards. The goal is to identify
gaps and to discuss new requirements to fill these gaps. In many
cases network services traverse several carriers and regions, and
in long distance services this is the most probable case. A multi-
carrier and multi-regional environment poses special technical and
commercial OAM requirements that should be defined and addressed.
In particular, OAM in multi-carrier networks has commercial
aspects that do not exist in single carrier networks. Indeed, in
case of failure or out-of-SLA service delivery, the violating
carrier should compensate its partner carriers or the end
customer. Based on the information made available by the OAM
tools, the carriers should agree on the root cause.
Unfortunately, at present no reliable means to carry out this OAM
based compensation procedure are available in existing standards.
Furthermore, the out-of-service duration is a significant factor
when calculating the compensation/penalty in case of failure. Yet,
currently, each service provider measures the out-of-service
duration independently; as a result, it is difficult to agree on
the out-of-service duration and, as a consequence, on the amount
of compensation. The existing standards for OAM in transport
networks do not clearly address the above mentioned problems;
therefore, in a multi-carrier environment, the following
requirements may be specifically defined by considering that
Inter-carrier OAM should address or reference how inter-region or
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inter-technology requirements are addressed. Technological inter-
operability issues and inter-region OAM issues should be addressed
separately to inter-carrier considerations.
A. Inter-carrier OAM system should be supported by MEs that are
handled by different operators (carriers).
B. Inter-carrier OAM system should provide in-service reliable
means to the network service providers (NSPs) to prove, in case of
failure, which is the failing transit carrier or transit NSP etc.
C. Inter-carrier OAM system should provide optional in-service
notification messages that could be used to inform on-path service
NSPs of other on-path NSPs service degradation. This includes for
example any deviation from the SLA agreement and related
parameters (Jitter, Packet Loss, Throughput etc.).
D. Inter-carrier OAM system should provide reliable means to
measure an NSP's out-of-service provisioning duration; such
measurement could be agreed by all involved parties.
E. Inter-carrier OAM should provide means for confidentiality and
privacy between involved carriers.
F. Inter-carrier OAM should have the option of disclosing
information forwarded by transit NSPs that are not involved under
the same inter-carrier OAM agreement.
4 Conclusions
The exiting OAM standards do not clearly differentiate between
inter-carrier, inter-region (inter-technology) as well as
different layer defined OAM requirements such as on the network
level, service level etc. This draft aimed to achieve this and
focuses on the inter-carrier requirements only. The majority of
these requirements were derived from the nature of service
provisioning between different network service providers.
OAM is an essential tool set for network operation and service
provisioning, and in case of inter-carrier it can help to settle
responsibility disputes in case of failures and performance
degradations. This document reviews the existing OAM standards,
identifies gaps, and discusses new requirements for the inter
domain and inter carrier scenarios.
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5 References
[RFC5860] Vigourex, M., Ward, D., Betts, M., Bocci, M., Busi, I.,
"Requirements for Operations, Administration, and
Maintenance (OAM) in MPLS Transport Networks", RFC 5860,
May 2010.
[I.610] ITU-T Recommendation I.610, "B-ISDN operation and maintenance
principles and functions", February 1999.
[IEEE1] IEEE 802.3-2008, IEEE Standard for Information technology -
Telecommunications and information exchange between
systems--Local and metropolitan area networks--Specific
requirements Part 3: Carrier Sense Multiple Access with
Collision Detection (CSMA/CD) Access Method and Physical
Layer Specifications. Institute of Electrical and
Electronics Engineers, 2977 pages, ISBN: 9730738157979,
December 2008.
[IEEE2] IEEE 802.1ag, "Virtual Bridged Local Area Networks -
Amendment 5: Connectivity Fault Management, IEEE 802.1
Committee", December 2007.
[MEFOAM] MEF, "Service OAM Requirements & Framework - Phase 1
Technical Specification, Metro Ethernet Forum", April
2007.
[Y1710] ITU-T Recommendation Y.1710(2002), "Requirements for OAM
Functionality for MPLS Networks", January 2001.
[Y1730] Recommendation Y.1730, "Requirements for OAM functions in
Ethernet based networks", January 2004.
[Y1731] ITU-T Recommendation Y.1731 - OAM functions and mechanisms
for Ethernet based networks, January 2006.
[RFC5706] Harringhton, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions", RFC
5706, November 2009.
[RFC4378] Allan, D. , Nadeau, T., A framework for Multi-Protocol
Label Switching (MPLS) Operations and Management (OAM),
RFC4378, February 2006.
Acknowledgements
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This work has been partially supported by the EU ICT STRONGEST and EU
ICT ETICS projects. Some technological considerations and
requirements resulted from collaboration with the EU ICT MAINS
Project.
Authors' Addresses
Michael Georgiades
Telecom Researcher (R&D)
The Maritime Center, PrimeTel PLC,
Omonia Avenue 141, 3045 Limassol, Cyprus
Email1: michaelg@prime-tel.com
Email2: m.georgiades@ieee.org
Filippo Cugini
CNIT National Lab of Photonic Networks
Scuola Superiore Sant'Anna (SSSUP)
via Moruzzi 1, 56124 Pisa, Italy
Email: filippo.cugini@cnit.it
David Berechya
Research, Multi-Layer Networks and Resilience
Nokia Siemens Networks
3 Hanagar St.
Hod Hasharon 45240, Israel
Email: david.berechya@nsn.com
Oscar Gonzalez
Telefonica I+D
Ramon de la Cruz, 82-84
Madrid, 28006
Email: ogondio@tid.es
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