Network Working Group Sanjeev Singh Internet-Draft W. Mark Townsley Category: Standards Track Jed Lau <draft-ietf-l2tpext-pwe3-atm-00.txt> Cisco Systems, Inc. March 2004 ATM Pseudo-Wire Extensions for L2TP Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract The Layer 2 Tunneling Protocol, Version 3, (L2TPv3) defines an extensible tunneling protocol, how to transport layer 2 services over IP network. This document describes the specifics of how to use the L2TP control plane for Asynchronous Transfer Mode (ATM) Pseudo-Wires and guidelines for transporting various ATM services over an IP network. Sanjeev, et al. Standards Track [Page 1]
INTERNET DRAFT ATM over L2TPv3 March 2004 Contents Status of this Memo.......................................... 1 1. Introduction.............................................. 3 1.1 Abbreviations......................................... 3 2. Control Connection Establishment.......................... 4 3. Session Establishment and ATM Circuit Status Notification. 4 3.1 L2TPv3 Session Establishment.......................... 4 3.2 L2TPv3 Session Teardown............................... 6 3.3 L2TPv3 Session Maintenance............................ 6 4. Encapsulation............................................. 7 4.1 ATM-Specific Sublayer................................. 7 4.2 Sequencing............................................ 9 5. ATM Transport............................................. 9 5.1 ATM AAL5-SDU Mode..................................... 10 5.2 ATM Cell Mode......................................... 10 5.2.1 ATM VCC Cell-Relay Service....................... 11 5.2.2 ATM VPC Cell-Relay Service....................... 11 5.2.3 ATM Port Cell-Relay Service...................... 12 5.3 OAM Cell Support...................................... 12 5.3.1 VCC switching.................................... 12 5.3.1 VPC switching.................................... 12 6. ATM Maximum Concatenated Cells AVP........................ 12 7. OAM Emulation Required AVP................................ 13 8. ATM defects mapping and status notification............... 13 8.1 ATM Alarm Status AVP.................................. 14 9. Security Considerations................................... 15 10. IANA Considerations...................................... 15 7. Acknowledgments........................................... 15 12. References............................................... 16 12.1 Normative References................................. 16 12.2 Informative References............................... 16 13. Contacts................................................. 17 Sanjeev, et al. Standards Track [Page 2]
INTERNET DRAFT ATM over L2TPv3 March 2004 Specification of Requirements In this document, several words are used to signify the requirements of the specification. These words are often capitalized. 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 [RFC2119]. 1. Introduction This document describes the specifics of how to use the L2TP for ATM pseudo-wires, including encapsulation, carrying various ATM services, such as, AAL5 SDU, ATM VCC/VPC/Port cell-relay over L2TP, and mapping ATM defects to L2TP SLI message to notify the peer LCCE. Any ATM specific AVPs or other L2TP constructs for ATM pseudo-wire (ATMPW) support will be defined here as well. Support for ATM Switched Virtual Path/Connection (SVP/SVC) and Switched/soft Permanent Virtual Path/Connection (SPVP/SPVC) are outside the scope of this document. The reader is expected to be very familiar with the terminology and protocol constructs defined in [L2TPv3]. 1.1 Abbreviations AIS Alarm Indication Signal ATMPW ATM Pseudo-wire AVP Attribute Value Pair CC Continuity Check OAM Cell CE Customer Edge HEC Header Error Control LAC L2TP Access Concentrator (See [L2TPv3]) LCCE L2TP control connection endpoint (See [L2TPv3]) MSB Most Significant Byte OAM Operation, Administration, and Management PE Provider Edge PSN Packet Service Network PWE3 Pseudo-wire Edge-to-edge emulation RDI Remote Defect Indicator SDU Service Data Unit SLI Set Link Info, an L2TP control message SVC Switched Virtual Connection SVP Switched Virtual Path SPVC Switched Permanent Virtual Connection SPVP Switched Permanent Virtual Path VC Virtual Circuit Sanjeev, et al. Standards Track [Page 3]
INTERNET DRAFT ATM over L2TPv3 March 2004 VCC Virtual Channel Connection VCI Virtual Channel Identifier VPC Virtual Path Connection VPI Virtual Path Identifier 2. Control Connection Establishment To emulate, ATM pseudo-wires using L2TP, an L2TP Control Connection as described in Section 3.3 of [L2TPv3] MUST be established. The SCCRQ and corresponding SCCRP MUST include the specific ATM PW type of TBA1 (See IANA Considerations Section), in the Pseudo-Wire Capabilities List as defined in Section 5.4.3 of [L2TPv3]. This identifies the control connection as able to establish L2TP sessions in support of the ATM Pseudo-Wires. An LCCE MUST be able to uniquely identify itself in the SCCRQ and SCCRP messages via a globally unique value. By default, this is advertised via the structured Router ID AVP [L2TPv3], though the unstructured Hostname AVP [L2TPv3] MAY be used if both endpoints support an application (as defined by the Application Code AVP [L2TPv3]) to identify LCCEs via this value. 3. Session Establishment and ATM Circuit Status Notification This section describes how L2TP ATM PW or sessions are established between two LCCEs. This includes what will happen when an ATM Circuit (e.g. AAL5 PVC) is created, deleted or changes state when circuit is alarmed. 3.1 L2TPv3 Session Establishment ATM Circuit (e.g. an AAL5 PVC) creation triggers establishment of a L2TP session using three-way handshake described in Section 3.4.1 of [L2TPv3]. An LCCE MAY initiate the session immediately upon ATM circuit creation, or wait until the Circuit state transitions to ACTIVE before attempting to establish a session for the ATM circuit. It MAY be preferred to wait until Circuit status transitions to ACTIVE to avoid wasting L2TP resources. The Circuit Status AVP (see Section 8) MUST be present in the ICRQ and ICRP messages, and MAY be present in the SLI message for ATM PWs. The following figures shows how the L2TP messages are exchanged to setup an ATM PWs after ATM Circuit (e.g. an AAL5 PVC) becomes ACTIVE. Sanjeev, et al. Standards Track [Page 4]
INTERNET DRAFT ATM over L2TPv3 March 2004 LCCE (LAC) A LCCE (LAC) B ------------------ -------------------- ATM Ckt Provisioned ATM Ckt Provisioned ATM Ckt ACTIVE ICRQ (status = 0x03) ----> ATM Ckt ACTIVE <----- ICRP (status = 0x03) L2TP session established OK to send data into PW ICCN -----> L2TP session established OK to send data into PW The following signaling elements are required for the ATM PW establishment. a. Pseudo-Wire Type: One of the following four attribute types can be present in PW Type AVP of [L2TPv3]. - ATM AAL5 SDU attribute type, TBA1 - ATM VCC Cell-Relay attribute type, TBA2 - ATM VPC Cell-Relay attribute type, TBA3 - ATM Port Cell-Relay attribute type, TBA4 The above Cell-Relay mode can also signal the ATM Cell-Packing AVP as described in Section 6. Other ATM PW types are outside the scope of this document. b. PW End ID: Each PW is associated with a PW End ID akin to the VC-ID in [PWE3ATM]. Two LCCEs of a PW would have the same PW End ID and its format is described in Section 5.4.4 of [L2TPv3]. This End ID AVP MUST be present in the ICRQ in order for the remote LCCE to associate the session to the ATM Circuit. The End Identifier AVP defined in [L2TPv3] is of opaque form, though ATMPW implementations MAY simply use a four-octet value that is known to both LCCEs (either by direct configuration, or some other means). The exact method of how this value is configured, retrieved, discovered, or otherwise determined at each LCCE is outside the scope of this document. As with the ICRQ, the ICRP is sent only after the ATM Circuit transitions to ACTIVE as well. If LCCE B had not been provisioned that ATM Circuit identified in the ICRQ, a CDN would have been immediately returned indicating that the circuit was not provisioned Sanjeev, et al. Standards Track [Page 5]
INTERNET DRAFT ATM over L2TPv3 March 2004 or available at this LCCE. LCCE A should then exhibit a periodic retry mechanism. The period and maximum number of retries MUST be configurable. An Implementation MAY send an ICRQ or ICRP before a PVC is ACTIVE, as long as the Circuit Status AVP reflects that the ATM Circuit is INACTIVE and an SLI is sent when the ATM Circuit becomes ACTIVE (see Section 8). The ICCN is the final stage in the session establishment, confirming the receipt of the ICRP with acceptable parameters to allow bidirectional traffic. 3.2 L2TPv3 Session Teardown When an ATM Circuit is unprovisioned (deleted) at either LCCE, the associated L2TP session MUST be torn down via the CDN message defined in Section 3.4.3 of [L2TPv3]. 3.3 L2TPv3 Session Maintenance All sessions established by a given control connection utilize the L2TP Hello facility defined in Section 4.4 of [L2TPv3] for session keepalive. This gives all sessions basic dead peer and path detection between LCCEs. If the control channel utilizing the Hello message is not in-band with data traffic over PSN, then other method MAY be used to detect the Session failure and it is left for further study. ATMPW over L2TP uses the Set Link Info (SLI) control message as defined in [L2TPv3] to signal ATM Circuit Status between LCCEs after initial session establishment. This includes ACTIVE or INACTIVE notifications of the ATM Circuit, or any other parameters that may need to be shared between the LCCEs in order to provide proper PW emulation. The SLI message MUST be sent any time there is a status change which may be reported by any values identified in the Circuit Status AVP. The only exception to this is the initial ICRQ, ICRP and CDN messages which establish and teardown the L2TP session itself when ATM circuit is created or deleted. The SLI message may be sent from either LCCE at any time after the first ICRQ is sent (and perhaps before an ICRP is received, requiring the peer to perform a reverse Session ID lookup). The other application of the SLI message is to map the ATM OAM or physical layer alarms into Circuit Status AVP as described in Section Sanjeev, et al. Standards Track [Page 6]
INTERNET DRAFT ATM over L2TPv3 March 2004 8. 4. Encapsulation The section describes the general encapsulation format for ATM services over L2TP. Figure 1: General format for ATM encapsulation over L2TPv3 over IP 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PSN Transport Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Session Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ATM-Specific Sublayer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | ATM Service Payload | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The PSN Transport header is specific to IP and its underlying transport header. This header is used to transport the encapsulated ATM payload through the IP network. The Session Header is non-zero 32-bit session ID and optional cookies upto 64-bits. This Session id is exchanged during session setup. The ATM Specific Sublayer is REQUIRED for AAL5 SDU mode and OPTIONAL for ATM Cell mode. Please refer the Section 4.1 for more details. 4.1 ATM-Specific Sublayer An alternative to default L2-Specific Sublayer as mentioned in Section 4.6 of [L2TPv3], the ATM-Specific Sublayer is defined here. Four new flag bits (T,G,C,U) are defined which concurs with the Section 8.2 of [PWE3ATM]. The bit positions, 6 & 7 of MSB have already been defined in Section 4.5 of [L2TPFRAG] for fragmentation but are mutually exclusive with bits defined below. Figure 2: ATM-Specific Sublayer Format Sanjeev, et al. Standards Track [Page 7]
INTERNET DRAFT ATM over L2TPv3 March 2004 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |x|S|x|x|T|G|C|U| Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Definition of these four bits are as per Section 8.2 of [PWE3ATM] and also included here for reference. * S bit Definition of this bit as per Section 4.6 of [L2TPv3]. * xx (Reserved) These bits are reserved and MUST be set to 0 upon transmission and ignored upon reception, unless otherwise, these bits are used as per [L2TPFRAG]. * T (Transport type) bit Bit (T) of the control word indicates whether the packet contains an ATM admin cell or an AAL5 payload. If T = 1, the packet contains an ATM admin cell, encapsulated according to the VCC cell relay encapsulation of Section 5.2. If not set, the PDU contains an AAL5 payload. The ability to transport an ATM cell in the AAL5 SDU mode is intended to provide a means of enabling administrative functionality over the AAL5 VCC (though it does not endeavor to preserve user-cell and admin-cell arrival/transport ordering). * G (EFCI) Bit The ingress LCCE device SHOULD set this bit to 1 if the EFCI bit of the final cell of the incoming AAL5 payload is set to 1, or if the EFCI bit of the single ATM cell to be transported in the packet is set to 1. Otherwise this bit SHOULD be set to 0. The egress LCCE device SHOULD set the EFCI bit of all the outgoing cells that transport the AAL5 payload to the value contained in this field. * C (CLP) Bit The ingress LCCE device SHOULD set this bit to 1 if the CLP bit of any of the incoming ATM cells of the AAL5 payload are set to 1, or if the CLP bit of the single ATM cell that is to be transported in the packet is set to 1. Otherwise this bit SHOULD be set to 0. The egress LCCE device SHOULD set the CLP Sanjeev, et al. Standards Track [Page 8]
INTERNET DRAFT ATM over L2TPv3 March 2004 bit of all outgoing cells that transport the AAL5 CPCS-PDU to the value contained in this field. * U (Command/Response) Bit When FRF.8.1 Frame Relay / ATM PVC Service Interworking (see [FRF8.1]) traffic is being transported, the CPCS-UU Least Significant Bit (LSB) of the AAL5 CPCS-PDU may contain the Frame Relay C/R bit. The ingress LCCE device SHOULD copy this bit to the U bit of the control word. The egress LCCE device SHOULD copy the U bit to the CPCS-UU Least Significant Bit (LSB) of the AAL5 payload. The Sequence Number fields are described in Section 4.3 In case of a reassembly timeout, the encapsulating LCCE should discard all component cells of the AAL5 frame. An additional enumeration is added to the L2-Specific Sublayer AVP to identify the ATM L2-Specific Sublayer: 0 - There is no L2-Specific Sublayer present. 1 - The default L2-Specific Sublayer (defined in Section 4.6) is used. TBA5 - The ATM L2-Specific Sublayer is used. The first two values are already defined in the L2TPv3 base draft [L2TPv3]. 4.2 Sequencing Data Packet Sequencing MAY be enabled for ATMPWs. The sequencing mechanisms described in [L2TPv3] MUST be used for signaling sequencing support. ATMPW over L2TPv3 MUST request the presence of the ATM-Specific Sublayer when sequencing is enabled, and MAY request its presence at all times. 5. ATM Transport There are two encapsulations supported for ATM transport as described below. ATM Specific Sublayer is prepended to AAL5-SDU. The other Cell-mode encapsulation consists of the OPTIONAL ATM-Specific Sublayer and 4- byte ATM Cell Header and 48-byte ATM Cell-payload. Sanjeev, et al. Standards Track [Page 9]
INTERNET DRAFT ATM over L2TPv3 March 2004 5.1 ATM AAL5-SDU Mode In this mode each AAL5 VC is mapped to an L2TP session. Ingress LCCE reassembles AAL5 CPCS-SDU without AAL5 trailer and any padding bytes. Incoming EFCI, CLP and C/R (if present) is carried in ATM Specific sublayer across ATMPW to egress LCCE. The processing of these bits on ingress and egress LCCE defined in Section 4.1. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |x|S|x|x|T|G|C|U| Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | AAL5 CPCS-SDU | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ If ingress LCCE determines that an encapsulated AAL5 SDU exceeds the MTU size of the PW then AAL5 SDU should be discarded. F5 OAM cells that arrive during the reassembly of an AAL5 SDU are sent immediately on the PW followed by the AAL5 SDU payload. In this case OAM cell's relative order with respect to user data cell is not maintained. Performance Monitoring OAM, as specified in ITU-T 610 [I610-1], [I610-2], [I610-3] and security OAM cells as speicified in [ATMSEC], should not be used in combination with AAL5 SDU mode and these cells MAY be dropped at ingress LCCE because cell sequence integrities is not maintained. 5.2 ATM Cell Mode In this mode, ATM cells skip the reassembly process at ingress LCCE and transported over an L2TP session, either as a single Cell or as concatenated cells into a single packet. Each ATM Cell consists of 4 byte ATM cell header and 48-byte ATM Cell-payload, HEC is not included. In ATM Cell Mode encapsulation, ATM-Specific Sublayer is OPTIONAL. It can be included, if sequencing support required. It is left to implementation to choose to signal Default L2-Specific Sublayer or ATM-Specific Sublayer. Sanjeev, et al. Standards Track [Page 10]
INTERNET DRAFT ATM over L2TPv3 March 2004 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |x|S|x|x|x|x|x|x| Sequence Number (Optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | VPI | VCI |PTI |C| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | ATM Cell Payload (48-bytes) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ " " +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | VPI | VCI |PTI |C| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | ATM Cell Payload (48-bytes) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ In the simplest case, this encapsulation can be used to transmit a single ATM cell per Pseudo Wire PDU. However, in order to provide better Pseudo Wire bandwidth efficiency, several ATM cells may be optionally encapsulated into single Pseudo Wire PDU. The maximum number of concatenated cells in a packet is limited by the MTU size of the session and also by the ability of egress LCCE to process them. For more detail about ATM Maximum Concatenated cells, please refer to Section 6. 5.2.1 ATM VCC Cell-Relay Service A VCC cell relay service may be provided by mapping an ATM Virtual Channel Connection to a single Pseudo-Wire using cell mode encapsulation as defined in section 5.2. An LCCE may map one or more VCCs to a single PW. However, a service provider may wish to provision a single VCC to a PW in order to satify QOS or restoration requirement. 5.2.2 ATM VPC Cell-Relay Service A Virtual Path Connection cell relay service may be provided by mapping an ATM Virtual Path Connection to single Pseudo Wire using cell mode encapsulation as defined in section 5.2. An LCCE may map one or more VPCs to a single Pseudo Wire. Sanjeev, et al. Standards Track [Page 11]
INTERNET DRAFT ATM over L2TPv3 March 2004 5.2.3 ATM Port Cell-Relay Service ATM port cell relay service allows an ATM port to be connected to only one other ATM port. All ATM cells that are received at the ingress ATM port on the LCCE, is encapsulated as per section 5.2 into Pseudo wire PDU and sent to peer LCCE. Each LCCE MUST discard any idle/unassigned cells received on an ATM port associated with an ATM PW. 5.3 OAM Cell Support The OAM cells are defined in [I610-1], [I610-2], [I610-3] and [ATMSEC] can be categoried as: a. Fault Management b. Performance monitoring and reproting c. Activation/deactivation d. System Management (e.g. security OAM cells). OAM Cells are always encapsulated using cell mode encapsulation, regardless of the encapsulation format used for user data. 5.3.1 VCC switching The LCCEs SHOULD be able to pass the F5 segment and end-to-end Fault Management, Resource Management (RM cells), Performance Management, Activation/deactivation and System Management OAM cells. F4 OAM cells are inserted or extracted at the VP link termination. These OAM cells are not seen at the VC link termination and are therefore not sent across the PW. 5.3.1 VPC switching The LCCEs MUST be able to pass the F4 segment and end-to-end Fault Management, Resource Management (RM cells), Performance Management, Activation/deactivation and System Management OAM cells transparently according to [I610-1]. F5 OAM cells are not intesrted or extracted at the VP cross-connect. The LCCEs MUST be able to pass the F5 OAM cells transparently across the PW. 6. ATM Maximum Concatenated Cells AVP The "ATM Maximum Cells Concatenated AVP", Attribute type TBA6, indicates that the egress LCCE node can process a single PDU with Sanjeev, et al. Standards Track [Page 12]
INTERNET DRAFT ATM over L2TPv3 March 2004 concatenated cells upto a specified number of cells. An LCCE node transmitting concatenated cells on this PW MUST not exceed the maximum number of cells as specified in this AVP. This AVP is applicable only to ATM Cell-Relay PW types (VCC, VPC, Port Cell-Relay). This Attribute value may not be same in both direction of the specific PW. The Attribute Value field for this AVP has the following format: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ATM Maximum Concatenated Cells| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This AVP MAY be hidden (the H bit MAY be 0 or 1). The M bit for this AVP MAY be set to 0, but MAY vary (see Section 5.2 of [L2TPv3]). The length (before hiding) of this AVP is 8. This AVP is sent in an ICRQ, ICRP during session negotiation or via SLI control messages when LCCE changes the maximum number of Concatenated Cells configuration for given ATM cell-relay Circuit. 7. OAM Emulation Required AVP An "OAM Emulation Required AVP" Attribute type, TBA7 MAY be needed to signal OAM Emulation in AAL5 SDU mode if LCCE does not support transport of OAM cells across L2TP session. If OAM Cell Emulation is configured or detected via some other means on one side, the other LCCE MUST support OAM Cell Emulation as well. This AVP is exchanged during session negotiation (in ICRQ, ICRP) or during life of the session via SLI control message. If the other LCCE can not support the OAM Cell Emulation, the associated L2TP session MUST be torn down via CDN message with result code, TBA8. OAM Emulation AVP is a boolean AVP, having no Attribute Value. Its absence is FALSE and its presence is TRUE. This AVP MAY be hidden (the H bit MAY be 0 or 1). The M bit for this AVP SHOULD be set to 0, but MAY vary (see Section 5.2 of [L2TPv3]). The Length (before hiding) of this AVP is 6. 8. ATM defects mapping and status notification ATM OAM alarms or circuit status is indicated via Circuit Status AVP as defined in Section 5.4.5 of [L2TPv3]. For reference, usage of this AVP is shown below. Sanjeev, et al. Standards Track [Page 13]
INTERNET DRAFT ATM over L2TPv3 March 2004 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |A|N| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Value is a 16 bit mask with the two least significant bits defined and the remaining bits reserved for future use. Reserved bits MUST be set to 0 when sending, and ignored upon receipt. The A (Active) bit indicates whether the ATM Circuit is ACTIVE (1) or INACTIVE (0). The N (New) bit indicates whether the ATM circuit status indication is for a new Circuit (1) or an existing ATM Circuit (0). 8.1 ATM Alarm Status AVP An "ATM Alarm Status AVP" attribute type, TBA9 indicates the reason for the ATM circuit status and specific alarm type, if any, to its peer LCCE node. This OPTIONAL AVP MAY be present in SLI message with Circuit Status AVP. The Attribute Value field for this AVP has the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Circuit Status Reason | Alarm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Circuit status reason is a 2-octets unsigned integer and Alarm Type is also a 2-octets unsigned integer. This AVP MAY be hidden (the H bit MAY be 0 or 1). The m bit for this AVP SHOULD be set to 0, but MAY vary (see Section 5.2 of [L2TPv3]). The Length (before hiding) of this AVP is 10 octets. This AVP is sent in SLI message to indicate the additional information about the ATM circuit status. Circuit Status Reason values for the SLI message are as follows: 0 - Reserved CSR-TBA1 - No alarm or alarm cleared (default for Active Status) CSR-TBA2 - Unspecified or unknown Alarm Received (default for Inactive Status) CSR-TBA3 - ATM Circuit received F1 Alarm on ingress LCCE Sanjeev, et al. Standards Track [Page 14]
INTERNET DRAFT ATM over L2TPv3 March 2004 CSR-TBA4 - ATM Circuit received F2 Alarm on ingress LCCE CSR-TBA5 - ATM Circuit received F3 Alarm on ingress LCCE CSR-TBA6 - ATM Circuit received F4 Alarm on ingress LCCE CSR-TBA7 - ATM Circuit received F5 Alarm on ingress LCCE CSR-TBA8 - ATM Circuit down due to ATM Port shutdown on Peer LCCE CSR-TBA9 - ATM Circuit down due to loop-back timeout on ingress LCCE The general ATM Alarm failures are encoded as below: 0 - Reserved A-TBA1 - No Alarm type specified (default) A-TBA2 - Alarm Indication Signal (AIS) A-TBA3 - Remote Defect Indicator (RDI) A-TBA4 - Loss of Signal (LOS) A-TBA5 - Loss of pointer (LOP) A-TBA6 - Loss of framer (LOF) A-TBA7 - loopback cells (LB) A-TBA8 - Continuity Check (CC) 9. Security Considerations For generic security issues regarding PWs and ATMPWs, this document will eventually refer to documents from the PWE3 WG. 10. IANA Considerations The signaling mechanisms defined in this document rely upon the assignment of a ATM Pseudowire Type for ATM AAL5 SDU, ATM VCC Cell- relay, ATM VPC Cell-Relay, ATM Port Cell-Relay. IANA assignment of this value should take place within the PWE3 WG. This document defines a new ATM-Specific Sublayer and enumeration for L2-Specific Sublayer AVP to identify the ATM-Specific Sublayer. Two additional AVP Attribute (ATM Maximum Concatenated Cells AVP, OAM Emulation Required AVP) are specified in this document. These are required to be defined by IANA as described in Section 9.1 of [BCP0068]. This document defines one L2TP Result Codes in Section 7 and 8, which will be defined by IANA as described in Section 9.1 of [BCP0068]. 7. Acknowledgments Thanks for the contribution from Pony Zhu, Prasad Yaditi, Durai, Jaya Kumar, Sanjeev, et al. Standards Track [Page 15]
INTERNET DRAFT ATM over L2TPv3 March 2004 Thanks to Shoou Yiu and Fred Shu for their valuable time to review this document. 12. References 12.1 Normative References [L2TPv3] J. Lau, M. Townsley, A. Valencia, G. Zorn, I. Goyret, G. Pall, A. Rubens, B. Palter, Layer Two Tunneling Protocol a.k.a. "L2TPv3," work in progress, draft-ietf-l2tpext-l2tp-base-11.txt, October 2003. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 12.2 Informative References [PWE3ATM] L. Martini., et al., "Encapsulation Methods for Transport of ATM Cells/Frame Over IP and MPLS Networks", work in progress, draft-ietf-pwe3-atm-encap-01.txt [L2TPFRAG] A. Malis, W. M. Townsley, "PWE3 Fragmentation and Reassembly", draft-ietf-pwe3-fragmentation-00.txt [FRF8.1] "Frame Relay / ATM PVC Service Interworking Implementation Agreement (FRF 8.1)", Frame Relay Forum 2000. [BCP0068] Townsley, W., "Layer Two Tunneling Protocol (L2TP) Internet Assigned Numbers Authority (IANA) Considerations Update" RFC3438, BCP0068, December 2002 [I610-1] ITU-T Recommendation I.610 (1999): B-ISDN operation and maintenance principles and functions [I610-2] ITU-T Recommendation I.610, Corrigendum 1 (2000): B-ISDN operation and maintenance principles and functions (corrigendum 1) [I610-3] ITU-T Recommendation I.610, Amendment 1 (2000): B-ISDN operation and maintenance principles and functions (Amendment 1) [ATMSEC] ATM Forum Specification, af-sec-0100.002 (2001): ATM Security Specification version 1.1 Sanjeev, et al. Standards Track [Page 16]
INTERNET DRAFT ATM over L2TPv3 March 2004 13. Contacts Sanjeev Singh cisco Systems 170 W. Tasman Drive San Jose, CA 95134 sanjeevs@cisco.com W. Mark Townsley cisco Systems 7025 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 mark@townsley.net Jed Lau cisco Systems 170 W. Tasman Drive San Jose, CA 95134 jedlau@cisco.com Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." Sanjeev, et al. Standards Track [Page 17]
INTERNET DRAFT ATM over L2TPv3 March 2004 Intellectual Property The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11 [RFC2028]. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Sanjeev, et al. Standards Track [Page 18]
