--- 1/draft-ietf-mpls-tp-gach-dcn-01.txt 2009-05-13 20:12:08.000000000 +0200 +++ 2/draft-ietf-mpls-tp-gach-dcn-02.txt 2009-05-13 20:12:08.000000000 +0200 @@ -1,19 +1,19 @@ Networking Working Group D. Beller Internet-Draft Alcatel-Lucent Intended Status: Standards Track A. Farrel -Created: May 8, 2009 Old Dog Consulting -Expires: November 8, 2009 +Created: May 13, 2009 Old Dog Consulting +Expires: November 13, 2009 An Inband Data Communication Network For the MPLS Transport Profile - draft-ietf-mpls-tp-gach-dcn-01.txt + draft-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. @@ -36,79 +36,80 @@ 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 may be used to provide the + This document describes how the G-ACh may be 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). The document explains how MCN and SCN - packets are encapsulated, carried on the G-ACh, and demultiplexed for - delivery to the management or signaling/routing components on a label - switching router (LSR). + Communication Network (DCN). This document explains how MCN and SCN + messages 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 encapsulating or delivering native DCN messages. + 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]. + 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) packets in order to + a packet header format for use on pseudowires (PWs) in order to identify packets used for OAM and similar functions. - The use of the ACH is generalized to apply on any Multiprotocol Label - Switching (MPLS) Label Switching Path (LSP) in [GAL-GACH]. The - generalized concept is referred to as the Generic Associated Channel - (G-ACh) and is intended to create a control/communication channel + The use of the ACH is generalized in [GAL-GACH] and can be applied on + any Multiprotocol Label Switching (MPLS) Label Switching Path (LSP). + This is referred to as the Generic Associated Channel (G-ACh) and is + intended to create a control/management communication channel associated with the LSP that can be used to carry packets used for - OAM and similar functions (e.g., control plane messages). + OAM and similar functions (e.g., control/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]. + values is maintained by IANA [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 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. + The MPLS transport profile (MPLS-TP) is described in [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 in MPLS networks may be operated using + 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, 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]. + The G-ACh provides a suitable 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 @@ -142,92 +143,109 @@ 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. To send an MCC/SCC packet on the G-ACh, the MCC/SCC packet is - prepended with the ACH and one or more ACH TLVs [GAL-GACH], and MUST + G-ACh. The Channel Type field indicates the function of the ACH + message so, to send an MCC/SCC packet on the G-ACh, the MCC/SCC + message is prepended with an ACH with the Channel Type set to + indicate that the message is a MCC or SCC message. The ACH MUST include the ACH Protocol ID TLV [ACH-TLV] to identify the protocol - type of the MCC or SCC packet. + type of the MCC or SCC 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 Packet | + | MCC/SCC Message | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 1: MCC/SCC Packet with Associated Channel Header + Figure 1: G-ACh MCC/SCC Packet o 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. + the PPP protocol identifiers to distinguish different 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 section G-ACh is used, the GAL is added to the packet 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 MPLS section, the GAL is added to + the message 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 SHOULD be set to 1, and the - S-bit of the GAL MUST be set to 1. + [GAL-GACH]. The TTL field of the GAL MUST be set to 1, and the S-bit + of the GAL MUST be set to 1. - The DCN channel MUST NOT be used to trnasport user traffic and SHALL + The DCN channel MUST NOT be used to transport 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 discarded although a local system MAY increment a - counter or raise an event log. 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 and - MAY increment a counter or raise an event log. + SHALL be silently discarded, although a local system MAY increment a + counter that records discarded or errored packets, and MAY log an + 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, MAY increment a counter that + records discarded or errored messages, and MAY log an 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 @@ -259,27 +276,37 @@ [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 and Martin Vigoureux for - their contribution to this document. + The editors wish to thank Pietro Grandi, Martin Vigoureux, and Kam + Lam for their contribution to this document. 8. Authors' Addresses Dieter Beller Alcatel-Lucent Germany EMail: dieter.beller@alcatel-lucent.com Adrian Farrel Old Dog Consulting EMail: adrian@olddog.co.uk