Inter-Carrier OAM Requirements
draft-georgiades-opsawg-intercar-oam-req-01
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| Authors | Oscar Gonzalez de Dios , Michael Georgiades , David Berechya , Filippo Cugini | ||
| Last updated | 2011-11-24 (Latest revision 2011-05-24) | ||
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draft-georgiades-opsawg-intercar-oam-req-01
OPSAWG WG M. Georgiades
Internet-Draft PrimeTel
Intended Status: Informational F.Cugini
Expires: 27 May 2012 CNIT
D. Berechya
NSN
O. Gonzalez
TID
November 24, 2011
Inter-Carrier OAM Requirements
draft-georgiades-opsawg-intercar-oam-req-01.txt
Abstract
This draft specifies requirements for inter-carrier OAM supporting
end-to-end OAM functionality and mechanisms development in a multi-
operator environment. It reviews the already proposed OAM
requirements addressed in IETF [RFC5706, RFC5860], ITU-T [Y.1730],
MEF [MEFOAM] and IEEE [IEEE1, IEEE2] which were mainly proposed on a
per transport technology basis. This document specifies 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Inter-carrier OAM Gap Analysis . . . . . . . . . . . . . . . . 5
3.1. OAM single region/single carrier transport network
requirements . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. OAM for inter-carrier transport networks . . . . . . . . . 9
4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 List of Contributors . . . . . . . . . . . . . . . . . . . . 11
6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1 Introduction
OAM functionality is important in network operation and management
for simplifying the operation and to reduce cost. It supports
capabilities for fault management (including fault detection, fault
notification and fault isolation), as well as performance degradation
awareness. A distinction of inter-carrier OAM requirements is made
from just the inter-operability requirements between carriers. The
first may also cover technological issues and requirements which
relate to end-to-end service delivery crossing domains but which
could be agnostic to underlying transport technologies. This may also
take into account different commercial administration as well as
operation policies of carriers.
OAM operations have been considered for different data transport
technologies by different standard bodies. Some solution examples
include ATM OAM ITU-T I.610 [I.610], IEEE 802.3-2008 [IEEE1], ITU-T
Y.1730 [Y.1730], IETF RFC 5860, IETF RFC 5706 [RFC5706], IETF RFC
5860 [RFC5860]. These protocols have been designed by different
organizations in different standard bodies 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-working
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 [Y.1731] and RFC 5860 [RFC5860] list
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 transport technology basis. Although for
example interworking between such mechanisms have been proposed e.g.
MPLS-to-Ethernet OAM, inter-carrier OAM issues and associated service
related technological issues due to these have not been addressed
thoroughly. The later may result in the proposal of new
functionality/mechanisms on a more generic common level (transport
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technology agnostic) that can become more acceptable by operators for
inter-carrier operations.
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].
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.
Out-of-service OAM
It refers to OAM actions which are carried out while the data
traffic is interrupted.
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.
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On-path service NSP
A transit NSP who is used as a traffic carrier or service provider
of a particular service.
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 Gap Analysis
To handle different possible scenarios for OAM it is important to
first 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
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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 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.
Requirements for Operational, Administration and Maintenance have
already been defined in detail by ITU-T, IETF and MEF, regarding the
single-domain scenario.
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OAM Requirements considered so far depend mainly on the data
transport network technology they aim to support. RFC 5860 [RFC5860]
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
Providers (NSPs) may choose to use different OAM standards to monitor
their operation, maintenance and fault detection, checking network
devices possibly from different vendors, different models and
different releases. This could be due to the fact that an operator
may want to monitor different technological domains, different
topologies or even multiple heterogeneous domains and hence OAM at a
different plane or OSI stack level. Moreover a Network Service
Provider may want to achieve service OAM provisioning for reserved
resources across multiple-carriers. 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 e.g. for ensuring end-
to-end network support for a particular service.
Current OAM functionalities do not guarantee network OAM aligned to a
associated with a particular service. The majority of OAM standards
are there to support network transport technologies and are not
sufficient to adequately support end-to-end network services in
inter-carrier scenarios. Inter-working between OAM for different
technologies may not be sufficient to achieve inter-carrier OAM
cooperation.
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 derived from the need to
satisfy network operation associated to a particular service but also
technical requirements derived from inter-carrier business
considerations associated to a particular service.
Inter carrier OAM involves any technological and technical aspects,
that once developed will motivate synergy between operators for OAM
and will offer more reliable and trustful means for co-operation.
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, and one carriers may not rely on the other carrier's
measuring.
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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
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,
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 are 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:
Continuity check / verification, Alarm suppression, Lock indication,
Diagnostic test, Trace-route, 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); (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; OAM frames should be
prevented from "leaking" outside the appropriate OAM domain to which
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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 the existing standards do not have trusted
mechanism to support these commercial issues. 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 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
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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.
G. Inter-carrier OAM system MAY have the ability to interwork with
the PCE architecture and traffic engineering databases, aiming at
improving reliability and accuracy in path computations, and
performing correlation of OAM information for location and
tracking of failures.
4 Summary
The exiting OAM standards do not clearly address the specific
needs of: 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.
5 Acknowledgements
This draft has been produced by the following three projects which
are funded by the European Union's Seventh Framework Programme
(FP7/2007-2013):
STRONGEST (FP7-ICT-247674); http://www.ict-strongest.eu/);
ETICS (FP7-ICT-248567); http://www.ict-etics.eu/);
MAINS (FP7-ICT-247706; http://www.ist-mains.eu/);
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5.1 List of Contributors
Michael Georgiades, Primetel, Cyprus;
Filipo Cugini, CNIT, Italy;
David Berechya, NSN, Israel;
Oscar Gonzalez, TID (Telefonica), Spain;
Nurit Sprecher, NSN, Israel;
6 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
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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.
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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