Networking Working Group D. Beller Internet-Draft Alcatel-Lucent Intended Status: Standards Track A. Farrel Created: May
8,13, 2009 Old Dog Consulting Expires: November 8,13, 2009 An Inband Data Communication Network For the MPLS Transport Profile draft-ietf-mpls-tp-gach-dcn-01.txtdraft-ietf-mpls-tp-gach-dcn-02.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. Abstract The Generic Associated Channel (G-ACh) has been defined as a generalization of the pseudowire (PW) associated control channel to enable the realization of a control/communication channel associated with Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs), MPLS PWs, MPLS LSP segments, and MPLS sections between adjacent MPLS-capable devices. The MPLS Transport Profile (MPLS-TP) is a profile of the MPLS architecture that identifies elements of the MPLS toolkit that may be combined to build a carrier grade packet transport network based on MPLS packet switching technology. This document describes how the G-ACh may maybe used to provide the infrastructure that forms part of the Management Communication Network (MCN) and a Signaling Communication Network (SCN). Collectively, the MCN and SCN may be referred to as the Data Communication Network (DCN). TheThis document explains how MCN and SCN packetsmessages are encapsulated, carried on the G-ACh, and demultiplexed for delivery to the management or signaling/routing control plane components on a label switching router (LSR). It should be noted that the use of the G-ACh to provide connectivity for the DCN is intended for use only where the MPLS-TP network is not capable of encapsulating or delivering native DCN messages. 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 The associated channel header (ACH) is specified in [RFC4385]. It is a packet header format for use on pseudowire (PW) packetspseudowires (PWs) in order to identify packets used for OAM and similar functions. The use of the ACH is generalized to applyin [GAL-GACH] and can be applied on any Multiprotocol Label Switching (MPLS) Label Switching Path (LSP) in [GAL-GACH]. The generalized concept(LSP). This is referred to as the Generic Associated Channel (G-ACh) and is intended to create a control/communicationcontrol/management communication channel associated with the LSP that can be used to carry packets used for OAM and similar functions (e.g., controlcontrol/management plane messages). The purpose of a packet carried on the G-ACh is indicated by the value carried by the Channel Type field of the ACH and a registry of values is maintained by IANA [RFC4446].[RFC4446] and [RFC4385]. The combination of the ACH and the ACH TLVs that may be appended to the ACH is referred in this document as the G-ACh header. The MPLS transport profile (MPLS-TP) is described in [MPLS-TP].[MPLS-TP] and in [TP-REQ]. MPLS-TP is the application of MPLS to construct a packet transport network. It constitutes a profile of MPLS that enables operational models typical in transport networks, which includes additional OAM, survivability and other maintenance functions not previously supported by MPLS. Label Switching Routers (LSRs) in MPLS networks may be operated using management protocols or control plane protocols. Messaging in these protocols is normally achieved using IP packets exchanged over IP- capable interfaces. However, some LSRs in MPLS-TP networks may be constructed without support for direct IP encapsulation on their line-side interfaces and without access to an out-of-fiber data communication network. In order that such LSRs can communicate using management plane or control plane protocols channels must be provided and the only available mechanism is to use an MPLS label. The G-ACh provides a suitable mechanism,mechanism for this purpose, and this document defines processes and procedures to allow the G-ACh to be used to build a management communication network (MCN) and a signaling communication network (SCN) together known as the data communication network (DCN) [G.7712]. 1.1. Requirements The requirements presented in this section are based on those communicated to the IETF by the ITU-T. 1. A packet encapsulation mechanism must be provided to support the transport of MCN and SCN packets over the G-ACh. 2. The G-ACh carrying the MCN and SCN packets shall support the following application scenarios: a. The G-ACh interconnects two adjacent MPLS-TP nodes (used when the server layer does not provide a Management Communication Channel (MCC) or a Signalling Communication Channel (SCC)). b. The G-ACh is carried by a MPLS-TP tunnel that traverses another operator's domain (carrier's carrier scenario) 3. The G-ACh shall provide two independent channels: a MCC to build the MCN and a SCC to build the SCN. The G-ACh packet header shall indicate whether the packet is a MCC or an SCC packet in order to forward it to the management or control plane application for processing. 4. The channel separation mechanism shall allow the use of separate rate limiters and traffic shaping functions for each channel (MCC and SCC) ensuring that the flows do not exceed their assigned traffic profile. The rate limiter and traffic shaper are outside the scope of the MCC and SCC definition. 5. The G-ACh that carries the MCC and SCC shall be capable of carrying different OSI layer 3 (network layer) PDUs. These shall include IPv4, IPv6, and OSI PDUs. The G-ACh header of the MCC/SCC packet shall indicate which layer 3 PDU is contained in the payload field of the packet such that the packet can be forwarded to the related layer 3 process within the management and control plane application, respectively, for further processing. 6. The G-ACh is not required to provide specific security mechanisms. However, the management or control plane protocols that operate over the MCC or SCC are required to provide adequate security mechanisms in order not to be susceptible to security attacks. 2. Procedures Figure 1 depicts the format of an MCC/SCC packet that is sent on the G-ACh. ToThe Channel Type field indicates the function of the ACH message so, to send an MCC/SCC packet on the G-ACh, the MCC/SCC packetmessage is prepended with thean ACH and onewith the Channel Type set to indicate that the message is a MCC or moreSCC message. The ACH TLVs [GAL-GACH], andMUST include the ACH Protocol ID TLV [ACH-TLV] to identify the protocol type of the MCC or SCC packet.message, and MAY include further ACH TLVs. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|Version| Reserved | Channel Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ACH TLV Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ACH Protocol ID TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ zero or more other ACH TLVs ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MCC/SCC PacketMessage | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: G-ACh MCC/SCC Packet with Associated Channel Headero The Channel Type field determines whether the message is an MCC or an SCC message. See Section 4 for the codepoint assignments. o The ACH Protocol ID TLV identifies the PDU type of the MCC/SCC message. The ACH Protocol ID TLV is defined in [ACH-TLV] and uses the PPP protocol identifiers to distinguish different protocols.protocols [RFC1661]. When the G-ACh sender receives an MCC message that is to be sent over the MCC, the sender creates the G-ACh header, provides an ACH Protocol ID TLV indicating the MCC layer 3 PDU type, sets the Channel Type field to MCC, and prepends the MCC message with the G-ACh header. The same procedure is applied when a control plane message is to be sent over the SCC. In this case, the sender sets the Channel Type field to SCC. If the MPLS sectionG-ACh is used,associated with an MPLS section, the GAL is added to the packetmessage as defined in [GAL-GACH]. The TTL field MUST be set to 1, and the S-bit of the GAL MUST be set to 1. If the G-ACh is associated with an LSP, the GAL is added to the packet and the LSP label is pushed on top of the GAL as defined in [GAL-GACH]. The TTL field of the GAL SHOULDMUST be set to 1, and the S-bit of the GAL MUST be set to 1. The DCN channel MUST NOT be used to trnasporttransport user traffic and SHALL only be used to carry management or control plane messages. Procedures that ensure this such as deep packet inspection are outside the scope of this specification. When a receiver has received a packet on the G-ACh with the ACH Channel Type set to MCC or SCC, it SHALL look at the PID field carried in the ACH Protocol ID TLV. If the TLV is absent, the message SHALL be silently discardeddiscarded, although a local system MAY increment a counter that records discarded or raiseerrored packets, and MAY log an event log.event. If the PID value is known by the receiver it SHALL deliver the entire packet including the MCC/SCC message to the appropriate processing entity. If the PID value is unknown, the receiver SHALL silently discard the received Packet andpacket, MAY increment a counter that records discarded or raiseerrored messages, and MAY log an event log.event. It must be noted that according to [GAL-GACH] a receiver MUST NOT forward a GAL packet based on the GAL label as is normally the case for MPLS packets. If the GAL appears at the bottom of the label stack, it MUST be processed as described in the previous paragraph. Note that there is no requirement for MPLS-TP devices to support IP or OSI forwarding in the fast or slow paths. Thus, if a message is received on the MCC or SCC and is not targeted to an address of the receiving LSR, the LSR MAY discard the message as incorrectly received.received using whatever mechanisms are necessary according to layer 3 protocol concerned. 2.1. Pseudowire Setup Provider Edge nodes may wish to set up PWs using a singaling protocol that uses remote adjacencies (such as LDP [RFC5036]). In the absence of an IP-based control plane network, these PEs MUST first set up an LSP tunnel across the MPLS-TP network. This tunnel can be used both to carry the PW once it has been set up and to provide a G-ACh based DCN for control plane communications between t`he PEs. Note that messages delivered on the G-ACh MUST NOT be forwarded based on their payload (for example, IP, CLNS, etc). 3. Security Considerations The G-ACh provides a virtual link between LSRs and might be used to induce many forms of security attack. Protocols that operate over the MCN or SCN are REQUIRED to include adequate security mechanisms and implementations MUST allow operators to configure the use of those mechanisms. 4. IANA Considerations Channel Types for the Generic Associated Channel are allocated from the IANA PW Associated Channel Type registry defined in [RFC4446] and updated by [GAL-GACH]. IANA is requested to allocate two further Channel Types as follows: xx Management Communication Channel (MCC) yy Signaling Communication Channel (SCC) 5. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4385] Bryant, S., et al., "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006. [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", RFC 4446, April 2006 . [GAL-GACH] Vigoureux, M., Bocci, M., Ward, D., Swallow, G., and R. Aggarwal, "MPLS Generic Associated Channel", draft-ietf-mpls-tp-gach-gal, work in progress. [ACH-TLV] Bryant, S., "Definition of ACH TLVs", draft-bryant-xxxx, work in progress. 6. Informative References [MPLS-TP] Bryant, S., Bocci, M., Lasserre, M., "A Framework for MPLS in Transport Networks", draft-ietf-mpls-tp-framework, work in progress. [TP-REQ] B. Niven-Jenkins, Ed., D. Brungard, Ed., M. Betts, Ed., N. Sprecher, S. Ueno, "MPLS-TP Requirements", draft-ietf-mpls-tp-requirements, work in progress. [G.7712] ITU-T Recommendation G.7712, "Architecture and specification of data communication network", June 2008. [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994. [RFC5036] Andersson, L., Minei, I., and Thomas, B., "LDP Specification", RFC 5036, October 2007. 7. Acknowledgements The editors wish to thank Pietro Grandi andGrandi, Martin VigoureuxVigoureux, and Kam Lam for their contribution to this document. 8. 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