INTERNET-DRAFT B. Berry Category: Informational H. Holgate Expires: April 10, 2005 Cisco Systems,Inc. 10 March 2004 PPP Over Ethernet (PPPoE) Extensions for Credit Flow and Link Metrics draft-bberry-pppoe-credit-02.txt 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, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Copyright (C) The Internet Society (year). 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. 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. 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. Abstract The Point-to-Point Over Ethernet (PPPoE) Protocol [3] provides a standard method for encapsulating Point-to-Point Protocols (PPP) [1] over Ethernet. This document extends the PPPoE protocol with a credit based flow control mechanism and Link Quality Metric report. The PPPoE specification is also extended to allow TLV Tags in the PPP Session Stage. These extensions are optional to retain backwards compatibility and at the same time provide for future extendibility. Internet-Draft PPPoE with Credit Flow and Metrics March 2004 Table of Contents 1. Introduction................................................3 2. Conventions used in this document...........................4 3. Payload.....................................................4 4. Overview of Protocol Extensions.............................4 5. Discovery Stage.............................................4 5.1 PPPoE Active Discovery Request (PADR)...................4 5.2 PPPoE Active Discovery Session-confirmation (PADS)......5 5.3 PPPoE Active Discovery Session-Grant (PADG).............5 5.4 PPPoE Active Discovery Session-Credit Response (PADC)...6 5.5 PPPoE Active Discovery Quality (PADQ)...................7 6. PPP Session Stage...........................................8 7. Credit Flow Considerations..................................8 8. Other Considerations........................................9 9. Security Considerations.....................................9 10. Appendix A: Tag Values....................................10 11. Appendix B: Example Message Formats.......................12 12. Normative References......................................19 13. ContributorĘs Information.................................19 14. Contact Information.......................................19 Berry, Holgate Expires April 10, 2005 [Page 2] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 1. Introduction PPP over Ethernet (PPPoE) [3] is a method of establishing and encapsulating sessions between hosts and traffic aggregators (Access Concentrators) for PPP transport. This method of transporting PPP traffic works well when both session endpoints have similar bandwidth, forwarding, and buffering capabilities that do not vary over time. It is insufficient for applications with variable bandwidth and limited buffering. This document describes a method for extending PPPoE to support credit based session flow control and session based metrics exchanges for mobile radio network applications. In the diagram below PPPoE sessions between and access concentrator (IP routers) and a radio transmission system are used to represent individual radio neighbors. The radio transmission system establishes point to point Radio Link Protocol (RLP) sessions with its neighbors and establishes a corresponding PPPoE session for each neighbor with the transmission system's associated access concentrator (router). +--------+ +-------+ +-------+ +---- ---+ | Access | | Host | | Host | | Access | | Conc. |=======| Radio |~~~~~~~| Radio |=======| Conc. | +--------+ +-------+ +-------+ +--------+ | | | | | | |-PPPoE-| |--RLP--| |-PPPoE-| | | |-------------PPP Session---------------| The capabilities of the RF links between RLP neighbors may vary over time due to mobility and environmental conditions. In many instances, the radio transmission system has limited buffering capability to handle capacity changes in the RLP sessions. To limit buffering in the radio transmission system, a session flow control mechanism is necessary to provide dynamic buffering feedback to the router. From the router's perspective in the diagram, each PPPoE session between it and the radio transmission system represents a link to a routable peer. For efficient routing, a mechanism of assigning and dynamically updating a cost for each link (PPPoE session) is required. When a modified PPPoE session between the router and the radio is established, link metrics must be exchanged. When the RLP session capabilities change, link metric feedback is provided to the router. Berry, Holgate Expires April 10, 2005 [Page 3] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 2. 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 [2]. 3. Payload The Ethernet payload version field retains its value of 0x01. The extensions for credit flow control and link quality metrics are optional and backward compatible. 4. Overview of Protocol Extensions PPPoE has two distinct stages. There is a Discovery Stage and a PPP Session Stage. During the Discovery Stage, the Host can optionally request a flow controlled PPP Session Stage. Once the Access Concentrator acknowledges the Host flow control request, all PPP Session Stage traffic MUST be flow controlled. 5. Discovery Stage The packet exchange of the Discovery Stage is unchanged by this specification. The specifications of the Session Request (PADR) and the Session Confirmation (PADS) packets are extended to include the optional Credit Tag TLV. In addition, the optional Credit Grant (PADG) packet, the Credit Response (PADC) packet and the Link Quality Metric (PADQ) packets are introduced. 5.1 PPPoE Active Discovery Request (PADR) The PADR packet is extended to optionally contain a single Credit Tag TLV, indicating that the Host requests credit flow control for this session. The Credit Tag contains the Forward Credit Notification (FCN) and the Backward Credit Notification (BCN) to be applied to the PPP Session Stage. The FCN provides the initial credits granted to the Access Concentrator by the Host. The BCN value is set to 0. An example packet is shown in Appendix B. Berry, Holgate Expires April 10, 2005 [Page 4] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 5.2 PPPoE Active Discovery Session-confirmation (PADS) The PADS packet is extended to optionally contain a single Credit Tag TLV, indicating the Forward Credit Notification (FCN) and the Backward Credit Notification (BCN) of the PPP Session Stage. If the PADR contained a Credit Tag, then the Access Concentrator PADS packet indicates support for credit flow control by including a Credit Tag. The PADS Credit Tag FCN represents the number of credits being initially granted to the Host. The Credit Tag BCN is an echo of the number of credits that the Host had granted to the Access Concentrator in the previous PADR packet. Exchange of the Credit Tag TLV in the PADR and PADS indicates that credit flow control is supported by both the Access Concentrator and the Host for the designated PPP Session Stage. This is binding and MUST be followed for the entire duration of the PPP Session Stage. A sessionĘs credit binding MUST be established prior to any other credit indications can be exchanged. The Access Concentrator PADS SHOULD ONLY carry the Credit Tag in response to a Host PADR with Credits. If the Access Concentrator does not support credit flow, it should not include the Credit Tag in its PADS response. The Host MUST terminate a credit based session that can not be supported by the Access Concentrator. Credit Tags transmitted outside an established credit based session MUST be ignored. An example packet is shown in Appendix B. 5.3 PPPoE Active Discovery Session-Grant (PADG) The PPPoE Active Discovery Session-Grant (PADG) is a new packet defined in this specification. An Access Concentrator or Host MAY send a PADG at any time after the PADR/PADS exchange to grant incremental flow control credits. The CODE field is set to 0x0A and the SESSION_ID MUST be set to the unique value generated for this PPPoE Session. The peer may then transmit data until the credits are exhausted. When the peer receives a PADG packet, it adds the incremental credits to its working credit count and responds with a PPPoE Active Discovery Session-Credit (PADC) packet indicating the accumulated credits. The PADG packet MUST contain a single Credit Tag TLV, indicating the Forward Credit Notification (FCN) and the Backward Credit Notification (BCN) of the PPP Session. Berry, Holgate Expires April 10, 2005 [Page 5] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 The Credit Tag FCN indicates the number of incremental credits being granted to the peer. A value between 1 and 0x0ffff represent an incremental credit grant. The peer must add these credits to its accumulated transmit credit count. A value of 0x00 represents a NULL grant, meaning that there are no additional credits being granted. The Credit Tag BCN indicates the remaining absolute credits that have been granted by the peer. Once a credit has been granted, it MUST be honored. The largest number of outstanding credits at any time is 0xffff. The PADG packet MUST contain a single Sequence Number Tag TLV. This tag is used to carry a unique 16-bit sequence number to uniquely identify each request. The sequence number SHOULD be initialized to zero and incremented by one for each new PADG. For re-transmitted PADGs, the same sequence number that was used in the previous packet transmission is repeated. An example packet is shown in Appendix B. 5.4 PPPoE Active Discovery Session-Credit Response (PADC) The PPPoE Active Discovery Session-Credit Response (PADC) is a new packet defined in this specification. An Access Concentrator or Host MUST send a PADC in response to a PADG. The CODE field is set to 0x0B and the SESSION_ID MUST be set to the unique value generated for this PPPoE session. The PADC packet MUST contain a single Credit Tag TLV, indicating the Forward Credit Notification (FCN) and the Backward Credit Notification (BCN) of the PPPoE session, and any number of other Tag types. The Credit Tag FCN represents the absolute credits remaining that have granted to the peer. The Credit Tag BCN represents the remaining absolute credits that have been granted to the node from the peer. The PADG packet MUST contain a single Sequence Number Tag. The sequence number should be the sequence number associated with the PADG. An example packet is shown in Appendix B. Berry, Holgate Expires April 10, 2005 [Page 6] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 5.5 PPPoE Active Discovery Quality (PADQ) The PPPoE Active Discovery Quality (PADQ) is a new packet defined in this specification. An Access Concentrator or Host MAY send an optional PADQ at any time to query or report link quality metrics. When transmitting PPP streams over wireless links through radio modems, the quality of the RF link directly affects the throughput. The PPPoE Active Discovery Quality (PADQ) packet can be used by the radio modem to report RF link metrics. The CODE field is set to 0x0C and the SESSION_ID MUST be set to the unique value generated for this PPPoE session. The PADQ MUST carry a single Metric Tag TYPE, which contains the following fields: Receive only - is a bit that indicates if the link is bi- directional or receive only. A value of -1- indicates that the link is receive-only. Maximum data rate - is the maximum theoretical data rate, in kilobits per second (kbps), that the RF link is capable of providing. When metrics are reported, the maximum data rate MUST be reported. Current data rate - is the current data rate, in kilobits per second (kbps), achieved on the RF link. If there is no distinction between maximum data rate and current data rate, current data rate should equal to maximum data rate. Latency - is the transmission delay that a packet encounters as it is transmitted over the RF link. This is reported in absolute delay, milliseconds. If latency can not be calculated, a value of 0 should be reported. Resources - is a percentage, 0-100, representing the amount of remaining or available resources, such as battery power. If resources can not be calculated, a value of 100 should be reported. Relative Link Quality (RLQ) - is a non-dimensional number, 0-100, representing the relative link quality. A value of 100 represents a link of the highest quality. If the RLQ can not be calculated, a value of 100 should be reported. The PPPoE Active Discovery Quality (PADQ) packet can be used to query link metrics by setting the PADQ Metric Tag Length to zero. An example packet is shown in Appendix B. Berry, Holgate Expires April 10, 2005 [Page 7] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 6. PPP Session Stage This specification defines the optional use of TLV Tags in the PPP Session Stage The first field following the PPP Session Stage LENGTH MUST be checked. If the value is equal to the PPP Protocol identifier (0xc021), then normal packet (payload) processing occurs. When the field following the PPP Session Stage LENGTH is not the PPP Protocol identifier (0xc021), a TLV is assumed. In this case, the Tag length is subtracted from the overall payload length. The Credit Tag is the only optional TLV permitted in the PPP Session Stage. The Credit Tag TLV is used to support in-band flow control. A PPP Session Stage packet with Credits is shown in Appendix B. 7. Credit Flow Considerations For a given session, credit grants exchanged in the Discovery Stage, PADG-PADC, are referred to as out-of-band. Credit grants exchanged in the PPP Session Stage are referred to as in-band. Credit processing is only applied to the packets transmitted in the PPP Session Stage. Out-of-band credit management is handled by periodic exchange of the PPPoE Active Discovery Grant PADG and PPPoE Active Discovery Credit (PADC) packets. In-band credit management allows credits to be incrementally granted with each PPP Session Stage packet. This offers the greatest credit granting efficiency when traffic rates are high. Once agreed upon during the Discovery Stage, credit grants are required to transmit packets in the PPP Session Stage. A node must grant credits to its peer, before the peer can transmit packets to the granting node. Credits are granted incrementally in the forward direction. Locally a node manages the credits that it has granted to a peer as well as the credits that a peer has granted to it. Grants received from a peer are added to a local running credit counter. The accumulated credits are decremented with each packet the node transmits to the peer. When the running counter reaches zero, the node stops transmitting packets to the peer. To manage the credits that a node has granted, the node maintains a running counter. With each PPP Session Stage packet received from the peer, the running counter is decremented. When the running counter reaches zero, no additional packets are expected. The node Berry, Holgate Expires April 10, 2005 [Page 8] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 incrementally grants more credits to the peer to maintain packet flow. Packets received when granted credits have been exhausted are discarded. The largest possible credit limit is 0x0ffff. If an incremental credit grant causes the accumulated count to exceed this value, the max value is used. One unit of credit represents 64-bytes, so a grant of 4 credits translates to 256-bytes. 8. Other Considerations When a node does not receive a PADC packet within a specified amount of time, it should transmit a new PADG packet with zero credits, using the same sequence number and double the waiting period. A PADC response with the associated sequence number will indicate if the previously granted credits were accumulated or not. If not, the PADG with credits, with an incremented sequence number, should be transmitted. This process should be repeated until granted credits are properly acknowledged or as many times as desired. When a node does not receive a PADQ metric packet within a specified amount of time, it should resend the PADQ query packet and double the waiting period. This is repeated as many times as desired. A node may autonomously generate PADQ metric packets. The rate of autonomously generate PADQ metric packets may need to be throttled so not to overrun the peer. 9. Security Considerations No new security considerations are provided in this document. Berry, Holgate Expires April 10, 2005 [Page 9] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 10. Appendix A: Tag Values Feature Tag_Types and Tag_Values 0x0106 Credits This tag contains the Forward Credit Notification (FCN) and the Backward Credit Notification (BCN). The Credit Tag TLV is OPTIONAL with the PADR, PADS and the PPPoE data payload packet (ETHER_TYPE=8864). +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0106 | Tag Length=0x04 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FCN | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0x0107 Metrics This tag is used to report the link quality and performance. The Metrics Tag TLV contains the Receive Only indicator, Resource status, Latency, Relative Link Quality (RLQ), Current data rate and Maximum data rate. The Metrics TLV is required by the PADQ packet. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0107 | Tag Length=0x0A | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |R| RLQ | Resource | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Latency (MS) | Current Datarate (kbps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Maximum Datarate (kbps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0x0108 Sequence Number This tag is used to carry a unique 16-bit sequence number in order to identify a specific request and the associated response. The sequence number SHOULD be initialized to zero and incremented by one for each new request sequence number. For re-transmitted packets, the same sequence number that was used in the previous packet transmission is repeated. The PADG and PADC packets require the Sequence Number Tag. Berry, Holgate Expires April 10, 2005 [Page 10] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 For example, the sequence number sent in the PADG request is echoed in the PADC response. This ties a specific PADC response to a specific PADG request. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0108 | Tag Length=0x02 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 11] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 11. Appendix B: Example Message Formats A PADR packet with OPTIONAL Credit Tag Type 0x0106: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Access_Concentrator_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Access_Concentrator_mac_addr(c)| Host_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host_mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x19 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x0C | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0101 | Tag Length=0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0106 | Tag Length=0x04 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FCN | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 12] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PADS packet with OPTIONAL Credit Tag Type 0x0106: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Access_Concentrator_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Access_Concentrator_mac_addr(c)| Host_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host_mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x65 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x0C | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0101 | Tag Length=0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0106 | Tag Length=0x04 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FCN | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 13] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PADG packet with Credit Tag Type 0x0106: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination_mac_addr(c) | Source_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x0A | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x0E | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0108 | Tag Length=0x02 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | Tag Type = 0x0106 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Length=0x04 | FCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 14] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PADC packet with Credit Tag Type 0x0106: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination_mac_addr(c) | Source_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x0B | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x0E | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0108 | Tag Length=0x02 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | Tag Type = 0x0106 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Length=0x04 | FCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 15] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PADQ packet to query for the link metrics: This is indicated by the Metric Tag Length=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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Access_Concentrator_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Access_Concentrator_mac_addr(c)| Host_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host_mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x0C | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x08 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0101 | Tag Length=0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0107 | Tag Length=0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 16] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PADQ packet with Metric Tag Type 0x0107: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Access_Concentrator_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Access_Concentrator_mac_addr(c)| Host_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host_mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8863 | v = 1 | t = 1 | CODE = 0x0C | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0101 | Tag Length=0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0107 | Tag Length=0x0A | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |R| RLQ | Resource | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Latency (MS) | Current Datarate (kbps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Maximum Datarate (kbps) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 17] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 A PPP LCP packet with optional Credit Tag Type 0x0106: While the PPP protocol value is shown (0xc021), the PPP payload is left to the reader. This is a packet from the Host to the Access Concentrator. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Access_Concentrator_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Access_Concentrator_mac_addr(c)| Host_mac_addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host_mac_addr (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ETHER_TYPE = 0x8864 | v = 1 | t = 1 | CODE = 0x00 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SESSION_ID = 0x1234 | LENGTH = 0x???? | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag Type = 0x0106 | Tag Length=0x04 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FCN | BCN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PPP PROTOCOL = 0xc021 | PPP payload ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Berry, Holgate Expires April 10, 2005 [Page 18] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 12. Normative References [1] Simpson, W., Editor, "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Mamakos L., et. al., "A Method for Transmitting PPP Over Ethernet (PPPoE)", RFC 2516, February 1999. 13. ContributorĘs Information The authors would like to acknowledge the influence and contributions from Billy Moon and Fred Baker. 14. Contact Information Bo Berry Cisco 170 West Tasman Drive San Jose, CA 95134 USA email: bberry@cisco.com Howard Holgate Cisco 170 West Tasman Drive San Jose, CA 95134 USA email: hholgate@cisco.com Intellectual Property Statement 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. Copies of Berry, Holgate Expires April 10, 2005 [Page 19] Internet-Draft PPPoE with Credit Flow and Metrics March 2004 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 implementers 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. 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 assignees. 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Berry, Holgate Expires April 10, 2005 [Page 20]