Network Working Group Hing-Kam Lam Internet Draft Alcatel-Lucent Expires: October, 2009 Scott Mansfield Intended Status: Informational Eric Gray Ericsson April 15, 2009 MPLS TP Network Management Requirements draft-ietf-mpls-tp-nm-req-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on October 15, 2009. Abstract This document specifies the requirements necessary to manage the elements and networks that support an MPLS Transport Profile (MPLS-TP). This document is a product of a joint International Telecommunications Union - Telecommunications Standardization Sector (ITU-T) and Internet Engineering Task Force (IETF) effort to include a MPLS Transport Profile within the IETF MPLS architecture. The requirements are driven by the management functionality needs defined by ITU-T for packet transport networks. Gray, et al Expires October, 2009 [Page 1] Internet-Draft MPLS-TP NM Requirements April, 2009 Table of Contents 1. Introduction................................................3 1.1. Terminology............................................3 2. Management Interface Requirements...........................4 3. Management Communication Channel (MCC) Requirements.........4 4. Management Communication Network (MCN) Requirements.........5 5. Fault Management Requirements...............................5 5.1. Supervision Function...................................5 5.2. Validation Function....................................6 5.3. Alarm Handling Function................................7 5.3.1. Alarm Severity Assignment.........................7 5.3.2. Alarm Suppression.................................7 5.3.3. Alarm Reporting Control...........................8 5.3.4. Alarm Reporting...................................8 6. Configuration Management Requirements.......................8 6.1. System Configuration...................................9 6.2. Control Plane Configuration............................9 6.3. Path Configuration.....................................9 6.4. Protection Configuration...............................9 6.5. OAM Configuration.....................................10 7. Performance Management Requirements........................10 7.1. Path Characterization Performance Metrics.............10 7.2. Performance Measurement Instrumentation..............12 7.2.1. Measurement Frequency............................12 7.2.2. Measurement Scope................................12 8. Security Management Requirements...........................13 8.1. Management Communication Channel Security.............13 8.2. Signaling Communication Channel Security..............13 8.3. Distributed Denial of Service.........................13 9. Security Considerations....................................14 10. IANA Considerations......................................14 11. Acknowledgments...........................................14 12. References................................................14 12.1. Normative References.................................14 12.2. Informative References...............................15 13. Author's Addresses........................................16 Copyright Statement...........................................16 Acknowledgment................................................17 APPENDIX A: Communication Channel (CC) Examples...............18 Gray, et al Expires October, 2009 [Page 2] Internet-Draft MPLS-TP NM Requirements April, 2009 1. Introduction This document describes the requirements necessary to manage the elements and networks that support an MPLS Transport Profile (MPLS-TP). It leverages the management requirements specified in ITU-T G.7710/Y.1701 [1] and RFC 4377 [2]. ITU-T G.7710/Y.1701 [1] specifies generic management requirements for transport (including packet-based and circuit-based) networks. RFC 4377 specifies the OAM requirements, including OAM-related network management requirements, for MPLS networks. This document expands on the requirements in [1] and [2] to cover fault, configuration, performance, and security management for MPLS-TP networks, and the requirements for object and information models needed to manage MPLS-TP Networks and Network Elements. 1.1. Terminology Although this document is not a protocol specification, 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 [6] and are to be interpreted as instructions to protocol designers producing solutions that satisfy the requirements set out in this document. MPLS-TP NE: a network element (NE) that supports MPLS-TP functions MPLS-TP network: a network in which MPLS-TP NEs are deployed Data Communication Network (DCN): a network that supports Layer 1 (physical layer), Layer 2 (data-link layer), and Layer 3 (network layer) functionality for distributed management communications related to the management plane, for distributed signaling communications related to the control plane, and other operations communications (e.g., order-wire/voice communications, software downloads, etc.). Management Communication Network (MCN): A DCN supporting management plane communication is referred to as a Management Communication Network (MCN). Signaling Communication Network (SCN): A DCN supporting control plane communication is referred to as a Signaling Communication Network (SCN). Gray, et al Expires October, 2009 [Page 3] Internet-Draft MPLS-TP NM Requirements April, 2009 Communication Channel (CC): a logical channel between network elements (NEs) that can be used - e.g. - for management plane application or control plane applications. The physical channel supporting the CC is technology specific. See APPENDIX A: Management Communication Channel (MCC): a CC dedicated for management plane communications. Signaling Communication Channel (SCC): a CC dedicated for control plane communications. The SCC may be used for GMPLS/ASON signaling and/or other control plane messages (e.g., routing messages). Operations System (OS): A system that performs the functions that support processing of information related to operations, administration, maintenance, and provisioning (OAM&P) for the networks, including surveillance and testing functions to support customer access maintenance. 2. Management Interface Requirements This document does not specify which management interface protocol should be the standard protocol for managing MPLS-TP networks. Managing an end-to-end connection across multiple operator domains where one domain is managed (for example) via NETCONF/XML or SNMP/SMI, and another domain via CORBA/IDL, is allowed. For the management interface to the management system, an MPLS- TP NE MAY actively support more than one management protocol in any given deployment. For example, an MPLS-TP NE may use one protocol for configuration and another for monitoring. The protocols to be supported are at the discretion of the operator. 3. Management Communication Channel (MCC) Requirements An MPLS-TP management network SHOULD support seamless management connectivity with remote MPLS-TP domains and NEs as well as with termination points located in NEs under control by a third party network operator. See ITU-T G.8601 [8] for example scenarios in multi-carrier multi-transport-technology environments. For management purpose, every MPLS-TP NE MUST connect to an OS either directly or indirectly via another MPLS-TP NE. When an MPLS-TP NE is connected indirectly to an OS, an MCC MUST be supported between the MPLS-TP NE and the other MPLS-TP NE. Gray, et al Expires October, 2009 [Page 4] Internet-Draft MPLS-TP NM Requirements April, 2009 4. Management Communication Network (MCN) Requirements Entities of the MPLS-TP management plane communicate via a DCN, or more specifically via the MCN. The MCN connects MPLS-TP NEs with management systems, NEs with NEs, and management systems with management systems. Transport DCN architecture and requirements are specified in ITU-T G.7712/Y.1703 [7], including network layer protocols and their interworking. As a practical requirement, MCN connections require addressing. See the section on addressing in [13] for further information. In order to have the MCN operate properly, a number of management functions for the MCN are required, including: . Retrieval of DCN network parameters to ensure compatible functioning, e.g. packet size, timeouts, quality of service, window size, etc.; . Establishment of message routing between DCN nodes; . Management of DCN network addresses; . Retrieval of operational status of the DCN at a given node; . Capability to enable/disable access to the DCN. 5. Fault Management Requirements The Fault Management functions within an MPLS-TP NE enable the supervision, detection, validation, isolation, correction, and reporting of abnormal operation of the MPLS-TP network and its environment. 5.1. Supervision Function The supervision function analyses the actual occurrence of a disturbance or fault for the purpose of providing an appropriate indication of performance and/or detected fault condition to maintenance personnel and operations systems. The MPLS-TP NE MUST support supervision of the OAM mechanisms that are deployed for supporting the OAM requirements defined in [3]. Gray, et al Expires October, 2009 [Page 5] Internet-Draft MPLS-TP NM Requirements April, 2009 The MPLS-TP NE MUST support the following transmission supervision functions: . Supervision of looping check functions used to detect loops in the data-plane forwarding path (which result in non- delivery of traffic, wasting of forwarding resources and unintended self-replication of traffic); . Supervision of the detection of failure in the sequence of a protocol exchange (e.g. automatic protection switching protocol); The MPLS-TP NE transmission-related supervision mechanisms MUST support the flexibility to be configured to perform on-demand or proactively. The MPLS-TP NE MUST support supervision for software processing e.g., processing fault, storage capacity problem, version mismatch, corrupted data, out of memory, etc. The MPLS-TP NE MUST support hardware-related supervision for interchangeable and non-interchangeable units, cable, and power problem. The MPLS-TP NE SHOULD support environment-related supervision for temperature, humidity, etc. 5.2. Validation Function Validation is concerned with the integration of Fault Causes into Failures. A Fault Cause indicates a limited interruption of the required transport function. A Fault Cause is not reported to maintenance personnel because it could exist only for a very short time. Note that some of these events however are summed up in the Performance Monitoring process, and when this sum exceeds a certain value, a Threshold Report can be generated. When the Fault Cause lasts long enough, an inability to perform the required transport function arises. This Failure condition is subject to reporting to maintenance personnel and/or an OS because corrective action might be required. Conversely, when the Fault Cause ceases after a certain time, clearing of the Failure condition is also subject to reporting. The MPLS-TP NE MUST perform persistency checks on fault causes before it declares a fault cause a failure. Gray, et al Expires October, 2009 [Page 6] Internet-Draft MPLS-TP NM Requirements April, 2009 A transmission failure SHALL be declared if the fault cause persists continuously for a configurable time (Time-D). The failure SHALL be cleared if the fault cause is absent continuously for a configurable time (Time-C). Typically the default time values would be as follows: Time-D = 2.5 +/- 0.5 seconds Time-C = 10 +/- 0.5 seconds These time values are as defined in G.7710 [1]. The failure declaration and clearing MUST be time stamped. The time-stamp SHALL indicate the time at which the fault cause is activated at the input of the fault cause persistency (i.e. defect-to-failure integration) function, and the time at which the fault cause is deactivated at the input of the fault cause persistency function. 5.3. Alarm Handling Function 5.3.1. Alarm Severity Assignment Failures might be categorized to indicate the severity or urgency of the fault. An MPLS-TP NE SHOULD support the flexibility of assignment of severity (e.g., Critical, Major, Minor, Warning) by the management system. See G.7710 [1] for more description about alarm severity assignment. 5.3.2. Alarm Suppression Alarms may be generated from many sources, including OAM, device status, etc. An MPLS-TP NE MUST provide alarm suppression functionality that prevents the generation of superfluous alarms. Examples of alarm suppression mechanisms include simply discarding the alarms (or not generating them in the first place), or aggregating the alarms together, thereby greatly reducing the number of alarm notifications to be emitted. Gray, et al Expires October, 2009 [Page 7] Internet-Draft MPLS-TP NM Requirements April, 2009 Note: An MPLS-TP NE supporting the inter-working of one or more networking technologies (e.g., Ethernet, SDH/SONET, MPLS) with MPLS-TP needs to translate an MPLS-TP fault into an existing transport technology failure condition for reporting to the management system. See RFC 4377 [2] for more description. 5.3.3. Alarm Reporting Control Alarm Reporting Control (ARC) supports an automatic in-service provisioning capability. Alarm reporting MAY be turned off on a per-managed entity (e.g., LSP) basis to allow sufficient time for customer service testing and other maintenance activities in an "alarm free" state. Once a managed entity is ready, alarm reporting is automatically turned on. An MPLS-TP NE SHOULD support the Alarm Reporting Control function for controlling the reporting of alarm conditions. See G.7710 [1] and RFC 3878 [9] for more description of ARC. 5.3.4. Alarm Reporting Alarm Reporting is concerned with the reporting of relevant events and conditions, which occur in the network (including the NE, incoming signal, and external environment). Local reporting is concerned with automatic alarming by means of audible and visual indicators near the failed equipment. An MPLS-TP NE MUST support local reporting of alarms. The MPLS-TP NE MUST support reporting of alarms to an OS. These reports are either autonomous reports (notifications) or reports on request by maintenance personnel. The MPLS-TP NE SHOULD report local (environmental) alarms to a network management system. 6. Configuration Management Requirements Configuration Management provides functions to identify, collect data from, provide data to and control NEs. Specific configuration tasks requiring network management support include hardware and software configuration, configuration of NEs to support transport paths (including required working and Gray, et al Expires October, 2009 [Page 8] Internet-Draft MPLS-TP NM Requirements April, 2009 protection paths), and configuration of required path integrity/connectivity and performance monitoring (i.e. - OAM). 6.1. System Configuration The MPLS-TP NE MUST support the configuration requirements specified in G.7710 [1] for hardware, software, and date/time. 6.2. Control Plane Configuration If a control plane is supported in an implementation of MPLS-TP, the MPLS-TP NE MUST support the configuration of MPLS-TP control plane functions by the management plane. Further detailed requirements might be provided along with progress in defining the MPLS-TP control plane in appropriate specifications. 6.3. Path Configuration The MPLS-TP NE MUST support the capability of configuring required path performance characteristic thresholds (e.g. - Loss Measurement [LM], Delay Measurement [DM] thresholds). The MPLS-TP NE MUST support the capability of configuring required LSPs as follows: . configure LSP indentifier and/or other information necessary to retrieve LSP status information. 6.4. Protection Configuration The MPLS-TP NE MUST support the capability of configuring required path protection as follows: . Designate specifically identified LSPs as working or protection LSPs; . define associations of working and protection paths; . operate/release manual protection switching; . operate/release force protection switching; . operate/release protection lockout; . set/retrieve Automatic Protection Switching (APS) parameters, including - . Wait to Restore time, . Protection Switching threshold information. Gray, et al Expires October, 2009 [Page 9] Internet-Draft MPLS-TP NM Requirements April, 2009 6.5. OAM Configuration The MPLS-TP NE MUST provide the capability to configure the OAM entities and functions specified in [3]. The MPLS-TP NE MUST support the capability to choose which OAM functions to use and which maintenance entity to apply them. The MPLS-TP NE MUST support the capability to configure the OAM entities/functions as part of LSP setup and tear-down, including co-routed bidirectional point-to-point, associated bidirectional point-to-point, and uni-directional (both point-to-point and point-to-multipoint) connections. The MPLS-TP NE MUST support the configuration of maintenance entity identifiers (e.g. MEP ID and MIP ID) for the purpose of LSP connectivity checking. The MPLS-TP NE MUST have the flexibility to configure OAM parameters to meet their specific operational requirements, such as whether (1) one-time on-demand immediately or (2) one-time on-demand pre-scheduled or (3) on-demand periodically based on a specified schedule or (4) proactive on-going. The MPLS-TP NE MUST support the enabling/disabling of the connectivity check processing. The connectivity check process of the MPLS-TP NE MUST support provisioning of the identifiers to be transmitted and the expected identifiers. 7. Performance Management Requirements Performance Management provides functions to evaluate and report upon the behavior of the equipment, NE, and network for the purpose of Maintenance, Bring-into-service, Quality of service, and Performance monitoring for signal degradation. ITU-T Recommendation G.7710 [1] provides transport performance monitoring requirements for packet-switched and circuit-switched transport networks with the objective of providing coherent and consistent interpretation of the network behavior, in particular for hybrid network which consists of multiple transport technologies. The performance management requirements specified in this document are driven by such an objective. 7.1. Path Characterization Performance Metrics The MPLS-TP NE MUST support collection of loss measurement (LM) so that they can be used to detect performance degradation. Gray, et al Expires October, 2009 [Page 10] Internet-Draft MPLS-TP NM Requirements April, 2009 The MPLS-TP NE MUST support collection of delay measurement (DM) so that they can be used to detect performance degradation. The MPLS-TP NE MUST support reporting of Performance degradation via fault management for corrective actions (e.g. protection switching). The MPLS-TP NE MUST support collection of loss ratio measurement so that they can be used to determine Severely Errored Second (SES). A SES is declared for a one second interval when the ratio of lost packets to total transmitted packets in that one second interval exceeds a predetermined threshold. The packet lost threshold for declaring SES MUST be configurable. The number of SESs MUST be collected per configurable intervals (e.g. 15-minute and 24-hour). The MPLS-TP NE MUST support collection of SES measurement so that they can be used to determine service unavailable time. A period of unavailable time (UAT) begins at the onset of 10 consecutive SES events. These 10 seconds are considered to be part of unavailable time. A new period of available time begins at the onset of 10 consecutive non-SES events. These 10 seconds are considered to be part of available time. The MPLS-TP NE MUST support collection of Unavailable Seconds (UAS) so that they can be used to determine service availability. The number of UAS MUST be collected per configurable intervals (e.g. 15-minute and 24-hour). SES and UAS history (the number of readings to be retained and available) is as defined in ITU and ANSI documents associated with specific transport technologies (for instance, ITU-T G.7710, and ANSI T1.231-2003 [T1.231.01-2003 for DSL,.02 for DS1,.03 for DS3 and T1.231.04-2003 for SONET] - see [1] and [14] respectively), however these are fairly consistently defined as follows: - Current and previous 1-day statistics Gray, et al Expires October, 2009 [Page 11] Internet-Draft MPLS-TP NM Requirements April, 2009 - Current and 16 recent 15-minute statistics (ITU-T) - Current, previous and 31 recent 15-minute statistics (ANSI) Note that - worst case (ANSI) requires 2 copies of 1-day statistics (current and previous) and 33 copies of 15-minute statistics (current, previous and 31 recent). 7.2. Performance Measurement Instrumentation 7.2.1. Measurement Frequency The performance measurement mechanisms MUST support the flexibility to be configured to operate on-demand or proactively (i.e. continuously over a period of time). 7.2.2. Measurement Scope On measurement of packet loss and loss ratio: - For bidirectional (both co-routed and associated) P2P connections - . on-demand measurement of single-ended packet loss, and loss ratio, measurement are required; . proactive measurement of packet loss, and loss ratio, measurement for each direction are required. Note: for associated bidirectional P2P connections, this data can only be measured at end-points. - For unidirectional (P2P and P2MP) connection, proactive measurement of packet loss, and loss ratio, are required. On Delay measurement: - For unidirectional (P2P and P2MP) connection, on-demand measurement of delay measurement is required. - For co-routed bidirectional (P2P) connection, on-demand measurement of one-way and two-way delay are required. - For associated bidirectional (P2P) connection, on-demand measurement of one-way delay is required. Gray, et al Expires October, 2009 [Page 12] Internet-Draft MPLS-TP NM Requirements April, 2009 8. Security Management Requirements The MPLS-TP NE MUST support secure management and control planes. 8.1. Management Communication Channel Security Secure channels MUST be provided for all network traffic and protocols used to support management functions. This MUST include, at least, protocols used for configuration, monitoring, configuration backup, logging, time synchronization, authentication, and routing. The MCC MUST support application protocols that provide confidentiality and data integrity protection. If management communication security is provided, the MPLS-TP NE MUST support the following: - Use of open cryptographic algorithms (See RFC 3871 [5]) - Authentication - allow management connectivity only from authenticated entities. - Authorization - allow management activity originated by an authorized entity, using (for example) an Access Control List (ACL). Port Access Control - allow management activity received on an authorized (management) port. 8.2.Signaling Communication Channel Security Security considerations for the SCC are similar to the considerations driving the requirements described in section 8.1. Security Requirements for the control plane are out of scope for this document and are expected to be defined in the appropriate control plane specifications. Management of the control plane security must also be defined at that time. 8.3. Distributed Denial of Service Denial of Service (DoS) attack is an attack which tries to prevent a target from performing an assigned task, or providing its intended service(s), through any means. A Distributed DoS (DDoS) can multiply attack severity (possibly by an arbitrary amount) by using multiple (potentially compromised) systems to act as topologically (and potentially geographically) Gray, et al Expires October, 2009 [Page 13] Internet-Draft MPLS-TP NM Requirements April, 2009 distributed attack sources. It is possible to lessen the impact and potential for DDOS by using secure protocols, turning off unnecessary processes, logging and monitoring, and ingress filtering. RFC 4732 [4] provides background on DOS in the context of the Internet. 9. Security Considerations Section 8 includes a set of security requirements that apply to MPLS-TP network management. Solutions MUST provide mechanisms to prevent unauthorized and/or unauthenticated access to private information by network elements, systems or users. Performance of diagnostic functions and path characterization involves extracting a significant amount of information about network construction that the network operator MAY consider private. 10. IANA Considerations There are no IANA actions associated with this document. 11. Acknowledgments The authors/editors gratefully acknowledge the thoughtful review, comments and explanations provided by Adrian Farrel, Andrea Maria Mazzini, Ben Niven-Jenkins, Bernd Zeuner, Diego Caviglia, Dieter Beller, He Jia, Leo Xiao, Maarten Vissers, Neil Harrison and Rolf Winter. 12. References 12.1. Normative References [1] ITU-T Recommendation G.7710/Y.1701, "Common equipment management function requirements", July, 2007. [2] Nadeau, T., et al, "Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks", RFC 4377, February 2006. [3] Vigoureus, M., et al, "Requirements for OAM in MPLS Transport Networks", work in progress. Gray, et al Expires October, 2009 [Page 14] Internet-Draft MPLS-TP NM Requirements April, 2009 [4] Handley, M., et al, "Internet Denial-of-Service Considerations", RFC 4732, November 2006. [5] Jones, G., "Operational Security Requirements for Large Internet Service Provider (ISP) IP Network Infrastructure", RFC 3871, September 2004. [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [7] ITU-T Recommendation G.7712/Y.1703, "Architecture and Specification of Data Communication Network", June 2008. [8] ITU-T Recommendation G.8601, "Architecture of service management in multi bearer, multi carrier environment", June 2006. [9] Lam, H., et al, "Alarm Reporting Control Management Information Base (MIB)", RFC 3878, September 2004. 12.2. Informative References [10] Chisholm, S. and D. Romascanu, "Alarm Management Information Base (MIB)", RFC 3877, September 2004. [11] ITU-T Recommendation M.20, "Maintenance Philosophy for Telecommunication Networks", October 1992. [12] Telcordia, "Network Maintenance: Network Element and Transport Surveillance Messages" (GR-833-CORE), Issue 5, August 2004. [13] Bocci, M. et al, "A Framework for MPLS in Transport Networks", Work in Progress, November 27, 2008. [14] ANSI T1.231-2003, "Layer 1 In-Service Transmission Performance Monitoring", American National Standards Institute, 2003. [15] Vigoureux, M. et al, "MPLS Generic Associated Channel", draft-ietf-mpls-tp-gach-gal, work in progress. Gray, et al Expires October, 2009 [Page 15] Internet-Draft MPLS-TP NM Requirements April, 2009 13. Author's Addresses Editors: Scott Mansfield Ericsson 5000 Ericsson Drive Warrendale, PA, 15086 Phone: +1 724 742 6726 EMail: Scott.Mansfield@Ericsson.com Hing-Kam (Kam) Lam Alcatel-Lucent 600-700 Mountain Ave Murray Hill, NJ, 07974 Phone: +1 908 582 0672 Email: hklam@Alcatel-Lucent.com Eric Gray Ericsson 900 Chelmsford Street Lowell, MA, 01851 Phone: +1 978 275 7470 Email: Eric.Gray@Ericsson.com Author(s): Contributor(s): Adrian Farrel Old Dog Consulting Email: adrian@olddog.co.uk Copyright Statement Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license- info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Gray, et al Expires October, 2009 [Page 16] Internet-Draft MPLS-TP NM Requirements April, 2009 Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Gray, et al Expires October, 2009 [Page 17] Internet-Draft MPLS-TP NM Requirements April, 2009 APPENDIX A: Communication Channel (CC) Examples A CC may be realized in a number of ways. 1. The CC may be provided by a link in a physically distinct network. That is, a link that is not part of the transport network that is being managed. For example, the nodes in the transport network may be interconnected in two distinct physical networks: the transport network and the DCN. This is a "physically distinct out-of-band CC". 2. The CC may be provided by a link in the transport network that is terminated at the ends of the DCC and which is capable of encapsulating and terminating packets of the management protocols. For example, in MPLS-TP an single-hop LSP might be established between two adjacent nodes, and that LSP might be capable of carrying IP traffic. Management traffic can then be inserted into the link in an LSP parallel to the LSPs that carry user traffic. This is a "physically shared out-of-band CC." 3. The CC may be supported as its native protocol on the interface alongside the transported traffic. For example, if an interface is capable of sending and receiving both MPLS-TP and IP, the IP-based management traffic can be sent as native IP packets on the interface. This is a "shared interface out-of-band CC". 4. The CC may use overhead bytes available on a transport connection. For example, in TDM networks there are overhead bytes associated with a data channel, and these can be used to provide a CC. It is important to note that the use of overhead bytes does not reduce the capacity of the associated data channel. This is an "overhead-based CC". This alternative is not available in MPLS-TP because there is no overhead available. 5. The CC may provided by a dedicated channel associated with the data link. For example, the generic associated label (GAL) [15] may be used to label DCC traffic being exchanged on a data Gray, et al Expires October, 2009 [Page 18] Internet-Draft MPLS-TP NM Requirements April, 2009 link between adjacent transport nodes, potentially in the absence of any data LSP between those nodes. This is a "data link associated CC". It is very similar to case 2, and by its nature can only span a single hop in the transport network. 6. The CC may be provided by a dedicated channel associated with a data channel. For example, in MPLS-TP the GAL [15] may be imposed under the top label in the label stack for an MPLS-TP LSP to create a channel associated with the LSP that may carry management traffic. This CC requires the receiver to be capable of demultiplexing management traffic from user traffic carried on the same LSP by use of the GAL. This is a "data channel associated CC". 7. The CC may be provided by mixing the management traffic with the user traffic such that is indistinguishable on the link without deep-packet inspection. In MPLS-TP this could arise if there is a data-carrying LSP between two nodes, and management traffic is inserted into that LSP. This approach requires that the termination point of the LSP is able to demultiplex the management and user traffic. Such might be possible in MPLS-TP if the MPLS-TP LSP was carrying IP user traffic. This is an "in-band CC". These realizations may be categorized as: A. Out-of-fiber, out-of-band (types 1 and 2) B. In-fiber, out-of-band (types 2, 3, 4, and 5) C. In-band (types 6 and 7) The MCN and SCN are logically separate networks and may be realized by the same DCN or as separate networks. In practice, that means that, between any pair of nodes, the MCC and SCC may be the same link or separate links. It is also important to note that the MCN and SCN do not need to be categorised as in-band, out-of-band, etc. This definition only applies to the individual links, and it is possible for some nodes to be connected in the MCN or SCN by one type of link, and other nodes by other types of link. Furthermore, a Gray, et al Expires October, 2009 [Page 19] Internet-Draft MPLS-TP NM Requirements April, 2009 pair of adjacent nodes may be connected by multiple links of different types. Lastly note that the division of DCN traffic between links between a pair of adjacent nodes is purely an implementation choice. Parallel links may be deployed for DCN resilience or load sharing. Links may be designated for specific use. For example, so that some links carry management traffic and some carry control plane traffic, or so that some links carry signaling protocol traffic while others carry routing protocol traffic. It should be noted that the DCN may be a routed network with forwarding capabilities, but that this is not a requirement. The ability to support forwarding of management or control traffic within the DCN may substantially simplify the topology of the DCN and improve its resilience, but does increase the complexity of operating the DCN. See also RFC 3877 [10], ITU-T M.20 [11], and Telcordia document GR-833-CORE [12] for further information. Gray, et al Expires October, 2009 [Page 20]