Network Working Group A. Yegin, Ed. Internet-Draft Samsung AIT Expires: August 11, 2005 E. Njedjou France Telecom S. Veerepalli Qualcomm N. Montavont T. Noel LSIIT - University Louis Pasteur February 10, 2005 Link-layer Event Notifications for Detecting Network Attachments draft-ietf-dna-link-information-01.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, 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. This Internet-Draft will expire on August 11, 2005. Copyright Notice Copyright (C) The Internet Society (2005). All Rights Reserved. Abstract Certain network access technologies are capable of providing various link-layer status information to IP. Link-layer event notifications can help IP expeditiously detect configuration changes. This draft Yegin, et al. Expires August 11, 2005 [Page 1] Internet-Draft L2 Notifications for DNA February 2005 provides a non-exhaustive catalogue of information available from well-known access technologies. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Requirements notation . . . . . . . . . . . . . . . . . . 4 2. Link-Layer Event Notifications . . . . . . . . . . . . . . . . 5 2.1 GPRS/3GPP . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 cdma2000/3GPP2 . . . . . . . . . . . . . . . . . . . . . . 7 2.3 IEEE 802.11/WiFi . . . . . . . . . . . . . . . . . . . . . 8 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1 Normative References . . . . . . . . . . . . . . . . . . . . 13 6.2 Informative References . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15 A. Change History . . . . . . . . . . . . . . . . . . . . . . . . 17 Intellectual Property and Copyright Statements . . . . . . . . 18 Yegin, et al. Expires August 11, 2005 [Page 2] Internet-Draft L2 Notifications for DNA February 2005 1. Introduction It is not an uncommon occurrence for a node to change its point-of attachment to the network. This can happen due to mobile usage (e.g., a mobile phone moving among base stations) or nomadic usage (e.g., road-warrior case). A node changing its point-of attachment to the network may end up changing its IP subnet and therefore require re-configuration of IP-layer parameters, such as IP address, default gateway information, and DNS server address. Detecting the subnet change can usually use network-layer indications such as a change in the advertised prefixes (i.e., appearance and disappearance of prefixes). But generally reliance on such indications does not yield rapid detection, since these indications are not readily available upon node changing its point of attachment. The changes on the underlying link-layer status can be relayed to IP in the form of link-layer event notifications. Establishment and tear down of a link-layer connection are two basic events types. Additional information can be conveyed in addition to the event type, such as the identifier of the network attachment point, or network-layer configuration parameters obtained via the link-layer attachment process. It is envisaged that such event notifications can in certain circumstances be used to expedite the inter-subnet movement detection and reconfiguration process. For example, the notification indicating that the node has established a new link-layer connection can be used for immediately probing the network for a possible configuration change. In the absence of such a notification from the link-layer, IP has to wait for indications that are not immediately available, such as receipt of next scheduled router advertisement, unreachability of the default gateway, etc. It should be noted that a link-layer event notification does not always translate into a subnet change. Even if the node has torn down a link-layer connection with one attachment point and established a new connection with another, it may still be attached to the same IP subnet. For example, several IEEE 802.11 access points can be attached to the same IP subnet. Moving among these access points does not warrant any IP-layer configuration change. In order to enable an enhanced scheme for detecting change of subnet, we need to define link-layer event notifications that can be realistically expected from various access technologies. The objective of this draft is to provide a catalogue of link-layer events and notifications in various architectures. While this document mentions the utility of this information for detecting change of subnet (or, detecting network attachment - DNA), the Yegin, et al. Expires August 11, 2005 [Page 3] Internet-Draft L2 Notifications for DNA February 2005 detailed usage is left to other documents, namely DNA solution specifications. The document limits itself to the minimum set of information that is necessary for solving the DNA problem [I-D.ietf-dna-goals]. A broader set of information may be used for other problem spaces (e.g., anticipation-based Mobile IP fast handovers [I-D.ietf-mobileip-lowlatency-handoffs-v4] [I-D.ietf-mipshop-fast-mipv6]). Separate documents that are backward-compatible with this one can be generated to discuss further enhancements. These event notifications are considered with hosts in mind, although they may also be available on the network side (e.g., on the access points and routers). An API or protocol-based standard interface may be defined between the link-layer and IP for conveying this information. That activity is beyond the scope of this document. 1.1 Requirements notation 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]. Yegin, et al. Expires August 11, 2005 [Page 4] Internet-Draft L2 Notifications for DNA February 2005 2. Link-Layer Event Notifications Link-layer event notifications are considered to be one of the inputs to the DNA process. A DNA process is likely to take other inputs (e.g., presence of advertised prefixes, reachability of default gateways) before determining whether IP-layer configuration must be updated. It is expected that the DNA process can take advantage of link-layer notifications when they are made available to IP. While by itself a link-layer notification may not constitute all the input DNA needs, it can at least be useful for prompting the DNA process to collect further information (i.e., other inputs to the process). For example, the node may send a router solicitation as soon as it learns that a new link-layer connection is established. Two basic link-layer events are considered potentially useful to DNA process: link up and link down. Both of these events are deterministic, and their notifications are provided to IP-layer after the events successfully conclude. These events and notifications are associated with a network interface on the node. The IP module may receive simultaneous independent notifications from each one of the network interfaces on the node. Node's establishment of a link-layer connection with an attachment point that signifies the availability of IP service (i.e., being able to send and receive IP packets) between the two is considered a link up event. The attachment point is typically an access network element, such as an access point, a base station, or a wired switch [TO-DO: How about ad-hoc networks? Attached neighbors may be considered attachment points]. The actual event is managed by the link-layer of the node through execution of link-layer protocols and mechanisms. Once the event successfully completes within the link-layer, its notification must be delivered to the IP-layer. By the time the notification is delivered, the link-layer of the node must be ready to accept IP packets from the IP and the physical-layers. Link down event signifies the discontinuation of the IP service between the node and the attachment point. When the link-layer connection is physically or logically torn down and it can no longer carry IP packets, this is considered to be a link down event. Among these two events the first one to take place after an interface becomes enabled must be a link up event. During the time a network interface is enabled, it may go through a series of link up and down events. Each time the interface changes its point of attachment, a link down event with the previous attachment point must be followed by a link up event with the new one. Finally, when the network Yegin, et al. Expires August 11, 2005 [Page 5] Internet-Draft L2 Notifications for DNA February 2005 interface is disabled, this must generate a link down event. Each one of these events must generate a notification in order they occur. A node may have to change its IP-layer configuration even when the link-layer connection stays the same. An example scenario is the IPv6 subnet renumbering [RFC2461]. Therefore, there exists cases where IP-layer configuration may have to change even without the IP-layer receiving a link up notification. Therefore, a link-layer notification is not a mandatory indication of a subnet change. In addition to the type of the event (link up, link down), a link-layer notification may also optionally deliver information relating to the attachment point. Such auxiliary information may include identity of the attachment point (e.g., base station identifier), or the IP-layer configuration parameters associated with the attached subnet (e.g., subnet prefix, default gateway address, etc.). While merely knowing that a new link-layer connection is established may prompt DNA process to immediately seek other clues for detecting network configuration change, auxiliary information may constitute further clues (and even the final answers sometimes). In cases where there is a one-to-one mapping between the attachment point identifiers and the IP-layer configurations, learning the former can reveal the latter. Furthermore, IP-layer configuration parameters obtained during link-layer connection may be exactly what the DNA process is trying to discover (e.g., IP address configured during PPP link establishment). The link-layer process leading to a link up or link down event depends on the link technology. While a link-layer notification must always indicate the event type, the availability and types of auxiliary information on the attachment point depends on the link-layer technology as well. The following subsections examine three link-layer technologies and describe when a link-layer notification must be generated and what information must be included in it. The coverage on the link types may be expanded in the future [TO-DO: Add IEEE 802.3]. 2.1 GPRS/3GPP GPRS is an enhancement to the GSM data transmission architecture and capabilities, designed to allow for packet switching in user data transmission within the GPRS network as well as for higher quality of service for the IP traffic of Mobile Terminals with external Packets Data Networks such as the Internet or corporate LANs [GPRS][GPRS-LINK]. The GPRS architecture consists of a Radio Access Network and a packet domain Core Network. Yegin, et al. Expires August 11, 2005 [Page 6] Internet-Draft L2 Notifications for DNA February 2005 - The GPRS Radio Access Network is composed of Mobile Terminals (MT), a Base Station Subsystem and Serving GPRS Support Nodes (SGSN). - An IP Core Network that acts as the transport backbone of user datagrams between SGSNs and Gateway GPRS Support Nodes (GGSN). The GGSN ensures the GPRS IP core network connectivity with external networks, such as Internet or Local Area Networks. GGSN acts as the default IP gateway for the MT. A GPRS MT that wants to establish IP-level connections should first perform a GPRS attach to the SGSN. This should be followed by a request the GPRS network to settle the necessary soft state mechanism (GPRS tunneling protocol) between its serving SGSN and the GGSN. The soft state maintained between the MT, the SGSN and the GGSN is called a PDP Context. It is used for guaranteeing a negotiated quality of service for the IP flows exchanged between the GPRS MT and an external Packet Data Network such as Internet . It is only after the PDP Context has been established, address autoconfiguration and tunneling mechanism have taken place that the MT's IP packets can be forwarded to and from its remote IP peers. The aim of PDP Context establishment is also to provide IP-level configuration on top of the GPRS link-layer attachment. Successful establishment of a PDP Context on a GPRS signifies the availability of IP service to the MT. Therefore, this link-layer event must generate a link up event notification sent to IP-layer. With IPv4, the auxiliary information carried along with this notification MUST be the IPv4 address of the MT which is obtained as part of the PDP Context. With IPv6, the PDP Context activation response does not come along with a usable IPv6 address. Effectively, the IPv6 address received from the GGSN in the PDP address field of the message does not contain a valid prefix. The MN actually only uses the interface-identifier extracted from that field to form a link-local address, that it uses afterwards to obtain a valid prefix (e.g., by stateless [RFC2462][GPRS-CN] or stateful [RFC3315][GPRS-GSSA] address configuration). Therefore no IPv6-related auxiliary information is provided to IP-layer. Similarly, PDP Context deactivation must generate a link down event notification. 2.2 cdma2000/3GPP2 cdma2000-based 3GPP2 packet data services provide mobile users wide area high-speed access to packet switched networks [CDMA2K]. Some of the major components of the 3GPP2 packet network architecture consist of: Yegin, et al. Expires August 11, 2005 [Page 7] Internet-Draft L2 Notifications for DNA February 2005 - Mobile Station (MS), which allows mobile access to packet-switched networks over a wireless connection. - Radio Access Network, which consists of the Base Station Transceivers, Base Station Controllers, and the Packet Control Function. - Network Access Server known as the Packet Data Switching Node (PDSN). The PDSN also serves as default IP gateway for the IP MS. 3GPP2 networks use the Point-to-Point Protocol (PPP [RFC1661]) as the link-layer protocol between the MS and the PDSN. Before any IP packets may be sent or received, PPP must reach the Network-Layer Protocol phase, and the IP Control Protocol (IPCP [RFC1332], IPV6CP [RFC2472]) reach the Opened state. When these states are reached in PPP, a link up event notification must be delivered to the IP-layer. When the PPP is used for 3GPP2 Simple (i.e., non-Mobile) IPv4 Service, IPCP enables configuration of IPv4 address on the MS. This IPv4 address must be provided as the auxiliary information along with the link up notification. IPV6CP used for Simple IPv6 service does not provide an IPv6 address, but the interface-identifiers for local and remote end-points of the PPP link. Since there is no standards-mandated correlation between the interface-identifier and other IP-layer configuration parameters, this information is deemed not useful for DNA (hence it is not provided as auxiliary information). IPCP/IPV6CP termination, or the underlying LCP or NCP reaching Closed State signify the end of corresponding IP service on the PPP link. This event must generate a link down notification delivered to the IP-layer. 2.3 IEEE 802.11/WiFi IEEE 802.11-based WiFi networks are the wireless extension of the Local Area Networks. Currently available standards are IEEE 802.11b [IEEE-802.11b], IEEE 802.11g [IEEE-802.11g], and IEEE 802.11a [IEEE-802.11a]. The specifications define both the MAC-layer and the physical-layer. The MAC layer is the same for all these technologies. Two operating modes are available in the IEEE 802.11 series, either infrastructure mode or ad-hoc mode. In infrastructure mode, all link-layer frames are transmitted to an access point (AP) which then forwards them to the final receiver. A STA must establish a IEEE 802.11 link with an AP in order to send and receive IP packets. In a WiFi network that supports Robust Secure Network (RSN Yegin, et al. Expires August 11, 2005 [Page 8] Internet-Draft L2 Notifications for DNA February 2005 [IEEE-802.11i]), successful completion of 4-way handshake between the STA and AP commences the availability of IP service. The link up event notification must be generated upon this event. In non-RSN-based networks, successful association or re-association events on the link-layer must cause a link up notification sent to the IP-layer. As part of the link establishment, Basic Service Set Identification (BSSID) and Service Set Identifier (SSID) associated with the AP is learned by the STA. BSSID is a unique identifier of the AP. Its value is set to the MAC address of the AP. SSID carries the identifier of the Extended Service Set (ESS) - the set composed of APs and associated STAs that share a common distribution system. BSSID and SSID should be provided as auxiliary information along with the link up notification. Unfortunately this information does not provide a deterministic indication of whether the IP-layer configuration must be changed upon movement. There is no standards-mandated one-to-one relation between the BSSID/SSID pairs and IP subnets. An AP with a given BSSID can connect a STA to any one of more than one IP subnets. Similarly, an ESS with the given SSID may span multiple IP subnets. And finally, the SSIDs are not globally unique. The same SSID may be used by multiple independent ESSs. See Appendix A of [DNA4] for a detailed discussion. Nevertheless, BSSID/SSID information may be used in a probabilistic way by the DNA process, hence it is provided with the link up event notification. Disassociation event in RSN-based, and de-authentication and disassociation events in non-RSN-based WiFi networks must translate to link down events, and generate the corresponding link-layer notifications. In ad-hoc mode, mobile station (STA) in range may directly communicate with others, i.e., without any infrastructure or intermediate hop. The set of communicating STAs is called IBSS for Indepedant Basic Service Set. In an IBSS, only station services are available, i.e. authentication, deauthentication, privacy and MSDU delivery. STAs do not associate with each other, and therefore may exchange data frames in state 2 (authenticated and not associated) or even in state 1 (unauthenticated and unassociated) if authentication is not used. Although a link up indication can be generated upon authentication, one may not be present per latter usage. If authentication is performed, a deauthentication event is used for generating the link down indication. Concerning the link layer identification, both the BSSID (which is a random MAC address chosen by a STA of the IBSS) and SSID may be used to identify a link, but not to make any assumptions on the IP network configuration. Yegin, et al. Expires August 11, 2005 [Page 9] Internet-Draft L2 Notifications for DNA February 2005 3. IANA Considerations This document has no actions for IANA. Yegin, et al. Expires August 11, 2005 [Page 10] Internet-Draft L2 Notifications for DNA February 2005 4. Security Considerations A faked link-layer event notification can be used to launch a denial-of service attack on the node and the associated network. Secure generation and delivery of these notifications must be ensured. This is a subject for link-layer and network stack designs and therefore it is outside the scope of this document. Yegin, et al. Expires August 11, 2005 [Page 11] Internet-Draft L2 Notifications for DNA February 2005 5. Acknowledgements The authors would like to acknowledge Bernard Aboba, Sanjeev Athalye, JinHyeock Choi, Greg Daley, Pekka Nikander, and Muhammad Mukarram bin Tariq for their useful comments and suggestions. Yegin, et al. Expires August 11, 2005 [Page 12] Internet-Draft L2 Notifications for DNA February 2005 6. References 6.1 Normative References [CDMA2K] "IS-835 - cdma2000 Wireless IP Network Standard", . [GPRS] "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS) Service description; Stage 2", 3GPP 3GPP TS 03.60 version 7.9.0 Release 98. [GPRS-LINK] "Digital cellular telecommunications system (Phase 2+); Radio subsystem link control", 3GPP GSM 03.05 version 7.0.0 Release 98. [I-D.ietf-dna-goals] Choi, J., "Detecting Network Attachment in IPv6 Goals", draft-ietf-dna-goals-04 (work in progress), December 2004. [IEEE-802.11a] Institute of Electrical and Electronics Engineers, "IEEE Std 802.11a-1999, supplement to IEEE Std 802.11-1999, Part 11: Wireless MAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHZ band", IEEE Standard 802.11a, September 1999. [IEEE-802.11b] Institute of Electrical and Electronics Engineers, "IEEE Std 802 Part 11, Information technology - Telecomunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 11: Wireless Lan Medium Access Control (MAC) And Physical Layer (PHY) Specifications", IEEE Standard 802.11b, August 1999. [IEEE-802.11g] Institute of Electrical and Electronics Engineers, "IEEE Std 802.11g-2003, Amendment to IEEE Std 802.11, 1999 edition, Part 11: Wireless MAN Medium Access Control (MAC) and Physical Layer (PHY) specifications. Amendment 4: Further Higher Data Rate Extension in the 2.4 GHz Band", IEEE Standard 802.11g, June 2003. [IEEE-802.11i] Institute of Electrical and Electronics Engineers, "Draft Supplement to STANDARD FOR Telecommunications and Information Exchange between Systems - LAN/MAN Specific Requirements - Part 11: Wireless Medium Access Control Yegin, et al. Expires August 11, 2005 [Page 13] Internet-Draft L2 Notifications for DNA February 2005 (MAC) and physical layer (PHY) specifications: Specification for Enhanced Security", IEEE Draft 802.11I/ D8, February 2004. [RFC1332] McGregor, G., "The PPP Internet Protocol Control Protocol (IPCP)", RFC 1332, May 1992. [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [RFC2472] Haskin, D. and E. Allen, "IP Version 6 over PPP", RFC 2472, December 1998. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. 6.2 Informative References [GPRS-CN] "Technical Specification Group Core Network; Internetworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN) (Release 6)", 3GPP 3GPP TS 29.061 version 6.1.0 2004-06. [GPRS-GSSA] "Technical Specification Group Services and System Aspect; General Packet Radio Service (GPRS) Service description; Stage 2 (Release 6)", 3GPP 3GPP TS 23.060 version 6.5.0 2004-06. [I-D.ietf-mipshop-fast-mipv6] Koodli, R., "Fast Handovers for Mobile IPv6", draft-ietf-mipshop-fast-mipv6-03 (work in progress), October 2004. [I-D.ietf-mobileip-lowlatency-handoffs-v4] Malki, K., "Low latency Handoffs in Mobile IPv4", draft-ietf-mobileip-lowlatency-handoffs-v4-09 (work in progress), June 2004. [RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Yegin, et al. Expires August 11, 2005 [Page 14] Internet-Draft L2 Notifications for DNA February 2005 Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. Authors' Addresses Alper E. Yegin (editor) Samsung Advanced Institute of Technology 75 West Plumeria Drive San Jose, CA 95134 USA Phone: +1 408 544 5656 EMail: alper.yegin@samsung.com Eric Njedjou France Telecom 4, Rue du Clos Courtel BP 91226 Cesson-SȨvignȨ, 35512 France Phone: +33 299124202 EMail: eric.njedjou@france-telecom.com Siva Veerepalli Qualcomm 5775 Morehouse Drive San Diego, CA 92131 USA Phone: +1 858 658 4628 EMail: sivav@qualcomm.com Nicolas Montavont LSIIT - University Louis Pasteur Pole API, bureau C428 Boulevard Sebastien Brant Illkirch, 67400 France Phone: +33 390 244 587 EMail: montavont@dpt-info.u-strasbg.fr Yegin, et al. Expires August 11, 2005 [Page 15] Internet-Draft L2 Notifications for DNA February 2005 Thomas Noel LSIIT - University Louis Pasteur Pole API, bureau C428 Boulevard Sebastien Brant Illkirch, 67400 France Phone: +33 390 244 592 EMail: noel@dpt-info.u-strasbg.fr Yegin, et al. Expires August 11, 2005 [Page 16] Internet-Draft L2 Notifications for DNA February 2005 Appendix A. Change History The following changes were made on draft version 00: - IEEE 802.11 ad-hoc mode discussion added. - IPv6 address configuration over 3GPP networks clarified. Yegin, et al. Expires August 11, 2005 [Page 17] Internet-Draft L2 Notifications for DNA February 2005 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 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 (2005). 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. Yegin, et al. Expires August 11, 2005 [Page 18]