Network Working Group Sanjeev Singh Internet-Draft W. Mark Townsley Category: Standards Track Jed Lau <draft-ietf-l2tpext-pwe3-atm-02.txt> Cisco Systems, Inc. October 2004 ATM Pseudo-Wire Extensions for L2TP Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 July 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............... 14 8.1 ATM Alarm Status AVP.................................. 14 9. Security Considerations................................... 15 10. IANA Considerations...................................... 15 10.1 L2-Specific Sublayer Type............................ 16 10.2 Control Message Attribute Value Pairs (AVPs)........ 16 10.3 Result Code AVP Values.............................. 16 10.4 ATM Alarm Status AVP Values......................... 17 11. Acknowledgments.......................................... 18 12. References............................................... 18 12.1 Normative References................................. 18 12.2 Informative References............................... 18 Sanjeev, et al. Standards Track [Page 2]
INTERNET DRAFT ATM over L2TPv3 July 2004 13. Authors' Addresses....................................... 19 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 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 Soft Permanent Virtual Connection SPVP Soft Permanent Virtual Path Sanjeev, et al. Standards Track [Page 3]
INTERNET DRAFT ATM over L2TPv3 July 2004 VC Virtual Circuit 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 supported ATM PW types (See Section 3.1), 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 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 in alarm. 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 in order 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 figure shows how 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 July 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 supported ATM related PW Types as defined in section 2 of [IANA] should be present in PW Type AVP of [L2TPv3]. 0x0002 ATM AAL5 SDU VCC transport 0x0003 ATM transparent cell transport 0x0009 ATM n-to-one VCC cell transport 0x000A ATM n-to-one VPC cell transport The above Cell-Relay mode can also signal the ATM Cell Concatenation AVP as described in Section 6. Other ATM PW types are outside the scope of this document. b. PW Remote End ID: Each PW is associated with a PW Remote End ID akin to the VC-ID in [PWE3ATM]. Two LCCEs of a PW would have the same PW Remote End ID and its format is described in Section 5.4.4 of [L2TPv3]. This Remote End ID AVP MUST be present in the ICRQ in order for the remote LCCE to associate the session to the ATM Circuit. The Remote 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. If LCCE B had not been provisioned yet for the Sanjeev, et al. Standards Track [Page 5]
INTERNET DRAFT ATM over L2TPv3 July 2004 ATM Circuit identified in the ICRQ, a CDN would have been immediately returned indicating that the circuit was either not provisioned or is not 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. It confirms 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 whenever there is a status change which may be reported by any values identified in the Circuit Status AVP. The only exception to this are 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). Sanjeev, et al. Standards Track [Page 6]
INTERNET DRAFT ATM over L2TPv3 July 2004 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 8. 4. Encapsulation This 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 a non-zero 32-bit session ID with 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 to Section 4.1 for more details. 4.1 ATM-Specific Sublayer This section defines a new ATM-specific sublayer as, an alternative to default L2-Specific Sublayer as mentioned in Section 4.6 of [L2TPv3]. Four new flag bits (T,G,C,U) are defined which concur with Section 8.2 of [PWE3ATM]. Figure 2: ATM-Specific Sublayer Format Sanjeev, et al. Standards Track [Page 7]
INTERNET DRAFT ATM over L2TPv3 July 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|B|E|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 is as per Section 4.6 of [L2TPv3]. * B and E bits Definition of these bits as per Section 5.5 of [L2TPFRAG] 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 Sanjeev, et al. Standards Track [Page 8]
INTERNET DRAFT ATM over L2TPv3 July 2004 transported in the packet is set to 1. Otherwise this bit SHOULD be set to 0. The egress LCCE device SHOULD set the CLP 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-Specific Sublayer: 0 - There is no L2-Specific Sublayer present. 1 - The default L2-Specific Sublayer (defined in Section 4.6) is used. TBA-1 - The ATM-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 to signal 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- Sanjeev, et al. Standards Track [Page 9]
INTERNET DRAFT ATM over L2TPv3 July 2004 byte ATM Cell Header and 48-byte ATM Cell-payload. 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) are carried in ATM Specific sublayer across ATMPW to egress LCCE. The processing of these bits on ingress and egress are 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 L2TPv3 session, then AAL5 SDU may be fragmented as per [L2TPFRAG] or underneath Transport layer (IP, etc). 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 cells is not maintained. Performance Monitoring OAM, as specified in ITU-T 610 [I610-1], [I610-2], [I610-3] and security OAM cells as specified in [ATMSEC], should not be used in combination with AAL5 SDU mode. These cells MAY be dropped at ingress LCCE because cell sequence integrity is not maintained. 5.2 ATM Cell Mode In this mode, ATM cells skip the reassembly process at ingress LCCE. These cells are 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 is required. It is left to the 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 July 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 details 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 July 2004 5.2.3 ATM Port Cell-Relay Service ATM port cell relay service allows an ATM port to be connected to only another ATM port. All ATM cells that are received at the ingress ATM port on the LCCE, are 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 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 reporting 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 inserted 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 AVP-TBA-1, indicates that the egress LCCE node can process a single PDU with Sanjeev, et al. Standards Track [Page 12]
INTERNET DRAFT ATM over L2TPv3 July 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 directions 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 a given ATM cell-relay Circuit. This AVP is OPTIONAL. If egress LCCE is configured with maximum number of cells to be concatenated by ingress LCEE, it should signal to ingress LCCE. 7. OAM Emulation Required AVP An "OAM Emulation Required AVP" Attribute type, AVP-TBA-2 MAY be needed to signal OAM Emulation in AAL5 SDU mode, if LCCE can 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, RC-TBA-1. 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. Sanjeev, et al. Standards Track [Page 13]
INTERNET DRAFT ATM over L2TPv3 July 2004 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. 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |N|A| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Value is a 16 bit mask with the two least significant bits defined and the remaining bits are 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, AVP-TBA-3 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: Sanjeev, et al. Standards Track [Page 14]
INTERNET DRAFT ATM over L2TPv3 July 2004 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 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 allocation of following ATM Pseudowire Types (see Pseudo Wire Capabilities List as defined in 5.4.3 of [L2TPv3] and L2TPv3 Pseudowire Types in 10.6 of [L2TPv3]) by the IANA (number space created as part of publication of [L2TPv3]): Pseudowire Types ---------------- 0x0002 ATM AAL5 SDU VCC transport 0x0003 ATM transparent cell transport 0x0009 ATM n-to-one VCC cell transport 0x000A ATM n-to-one VPC cell transport This document defines a number of "magic" numbers to be maintained by Sanjeev, et al. Standards Track [Page 15]
INTERNET DRAFT ATM over L2TPv3 July 2004 the IANA. This section explains the criteria to be used by the IANA to assign additional numbers in each of these lists. The following subsections describe the assignment policy for the namespaces defined elsewhere in this document. These sections are for new registries to be added to the existing L2TP registry and maintained by IANA accordingly. 10.1 L2-Specific Sublayer Type This number space is managed by IANA as per [BCP0068]. The L2-Specific Sublayer Type is a 2 octet unsigned integer. The following enumeration value is to be assigned by Expert Review [RFC2434]. L2-Specific Sublayer Type ------------------------- TBA-1 - ATM L2-Specific Sublayer present 10.2 Control Message Attribute Value Pairs (AVPs) This number space is managed by IANA as per [BCP0068]. New AVPs requiring assignment in this document are encoded with "AVP-TBA-x," where "x" is 1, 2, 3... A summary of the three new AVPs follows: Control Message Attribute Value Pairs Attribute Type Description --------- ---------------------------------- AVP-TBA-1 ATM Maximum Concatenated Cells AVP AVP-TBA-2 OAM Emulation Required AVP AVP-TBA-3 ATM Alarm Status AVP 10.3 Result Code AVP Values This number space is managed by IANA as per [BCP0068]. New Result Code value for the CDN message is defined in section 7. Following is a summary: Result Code AVP (Attribute Type 1) Values Sanjeev, et al. Standards Track [Page 16]
INTERNET DRAFT ATM over L2TPv3 July 2004 ----------------------------------------- General Error Codes RC-TBA-1 - Session not established due to other LCCE can not support the OAM Cell Emulation, 10.4 ATM Alarm Status AVP Values This number space is managed by IANA as per [BCP0068]. New Attribute values for the SLI message is defined in section 8. Following is a summary: ATM Alarm Status AVP (Attribute Type AVP-TBA-3) Values ------------------------------------------------------ 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 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) Sanjeev, et al. Standards Track [Page 17]
INTERNET DRAFT ATM over L2TPv3 July 2004 11. Acknowledgments Thanks for the contribution from Pony Zhu, Prasad Yaditi, Durai, Jaya Kumar, and razor sharp review by Carlos Pignataro. Many Thanks to Srinivas Kotamraju for editorial review. 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-10.txt, August 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-06.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 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations section in RFCs", BCP 26, RFC 2434, October 1998. [IANA] L. Martini, W. M. Townsley, "IANA Allocations for pseudo Wire Edge to Edge Emulation (PWE3)", draft-ietf-pwe3-iana-allocation-07.txt [I610-1] ITU-T Recommendation I.610 (1999): B-ISDN operation and Sanjeev, et al. Standards Track [Page 18]
INTERNET DRAFT ATM over L2TPv3 July 2004 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 13. Authors' Addresses 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 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any Sanjeev, et al. Standards Track [Page 19]
INTERNET DRAFT ATM over L2TPv3 July 2004 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Sanjeev, et al. Standards Track [Page 20]
