Network Working Group Basavaraj. Patil Internet-Draft Nokia Intended status: Standards Track Frank. Xia Expires: April 17, 2007 Behcet. Sarikaya Huawei USA Syam. Madanapalli LogicaCMG JinHyeock. Choi Samsung AIT October 14, 2006 IPv6 Over IPv6 Convergence sublayer in WiMAX Networks draft-ietf-16ng-ipv6-over-ipv6cs-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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 April 17, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Patil, et al. Expires April 17, 2007 [Page 1] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 Abstract The WiMAX forum is defining the network architecture which enables Internet connectivity to mobile stations and IP hosts via the 802.16d/e radio interface. This document specifies the addressing and operation of IPv6 for hosts served by a WiMAX network. It recommends the assignment of a unique prefix to each host and allow the host to use multiple identifiers within that prefix, including support for randomly generated identifiers. IPv6 operation in WiMAX networks as explained in this document is based entirely on existing IETF specifications. The solution entailed herein is recommended for adoption by the WiMAX forum for IPv6 over the IPv6 convergence sublayer. Table of Contents 1. Conventions used in this document . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. IEEE 802.16d/e convergence sublayer support for IPv6 . . . . . 6 5. WiMAX network architecture . . . . . . . . . . . . . . . . . . 7 6. IPv6 link in WiMAX . . . . . . . . . . . . . . . . . . . . . . 9 6.1. IPv6 link establishment . . . . . . . . . . . . . . . . . 9 6.2. Maximum transmission unit . . . . . . . . . . . . . . . . 9 7. IPv6 prefix assignment . . . . . . . . . . . . . . . . . . . . 11 8. Router Discovery . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Router Solictation . . . . . . . . . . . . . . . . . . . . 12 8.2. Router Advertisement . . . . . . . . . . . . . . . . . . . 12 8.3. Router lifetime and periodic router advertisements . . . . 12 9. IPv6 addressing for hosts . . . . . . . . . . . . . . . . . . 13 9.1. Interface Identifier . . . . . . . . . . . . . . . . . . . 13 9.2. Duplicate address detection . . . . . . . . . . . . . . . 13 9.3. Stateless address autoconfiguration . . . . . . . . . . . 13 9.4. Stateful address autoconfiguration . . . . . . . . . . . . 13 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 13.1. Normative References . . . . . . . . . . . . . . . . . . . 17 13.2. Informative References . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . . . 20 Patil, et al. Expires April 17, 2007 [Page 2] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 1. Conventions used in this document In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [RFC2119] and indicate requirement levels for compliant implementations. Patil, et al. Expires April 17, 2007 [Page 3] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 2. Introduction IEEE 802.16d/e is the air interface specification underlying the WiMAX forums network architecture specification. The 802.16d/e [802.16e] specification includes the Phy and MAC details. This document specifies the operation of IPv6 over 802.16d/e in the context of the WiMAX network architecture. Specifically it is limited to the operation of IPv6 over the IPv6 convergence sublayer. The IPv6 convergence sublayer is a part of the 802.16e MAC. The IPv6 link between the mobile station (MS) and the access router (AR) is considered as a point-to-point link. Assignment of a unique prefix per MS is recommended in this document. The document provides a brief overview of the WiMAX network architecture at a high level and describes the addressing and, transmission and receiving of IPv6 packets, by an MS. Patil, et al. Expires April 17, 2007 [Page 4] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 3. Terminology The terminology is based on the definitions used in the network architecture specified by the WiMAX forum. BS - The WiMAX Base Station (BS) is a logical entity that embodies a full instance of the WiMAX MAC and PHY in compliance with the IEEE 802.16 suite of applicable standards. It provides the layer 1/2 connectivity between the network and the MS. MS - The mobile station is an IPv6 host that connects to the WiMAX network via an 802.16d/e module. Transport Connection - 802.16 MAC is connection oriented. Several types of connections are defined and these include broadcast, unicast and multicast. Each connection is uniquely identified by a 16 bit connection identifier (CID). A transport connection is a unicast connection intended for user traffic. A transport connection is identified by an uplink and downlink CID. The scope of the transport connection is between the MS and the BS. Access Service Network (ASN) - The ASN is defined as a complete set of network functions needed to provide radio access to a WiMAX subscriber. The ASN is the access network to which the MS attaches. The IPv6 access router is an entity within the ASN. Access Router (AR) - The Access router is the 1st hop default IPv6 router from the perspective of the MS. The AR is an entity that exists within the scope of an ASN. Patil, et al. Expires April 17, 2007 [Page 5] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 4. IEEE 802.16d/e convergence sublayer support for IPv6 IEEE 802.16d/e has specified multiple convergence sublayers (CS) in the MAC. The convergence sublayers and MAC specifications are available in [802.16e]. IPv6 can be implemented in two ways: 1. Over the IPv6 convergence sublayer or 2. Over Ethernet (which runs over Ethernet CS). The figure below shows the options for IPv6 implementation in WiMAX: -------------- --------------- | IPv6 | | IPV6 | -------------- --------------- | IPv6 CS | | Ethernet | | .......... | --------------- | MAC | | Ethernet CS | -------------- | ........... | | PHY | | MAC | -------------- --------------- IPv6 over IPv6 CS | PHY | --------------- IPv6 over Ethernet Figure 1: IPv6 over IPv6 CS and over Ethernet WiMAX forum has chosen IP CS as the default CS to be supported for IP connectivity. The scope of this document is limited to IPv6 operation over IPv6 CS only. Patil, et al. Expires April 17, 2007 [Page 6] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 5. WiMAX network architecture The WiMAX network architecture consists of the Access Service Network (ASN) and the Connectivity Service Network (CSN). The ASN is the access network which includes the BS and the AR in addition to other functions such as AAA, Mobile IP Foreign agent, Paging controller, Location Register etc. The CSN is the entity that provides connectivity to the Internet and includes functions such as Mobile IP Home agent and AAA. The figure below shows the WiMAX reference model: ------------------- | ---- ASN | |----| ---- | |BS|\ R6 -------| |---------| | CSN| |MS|-----R1----| ---- \---|ASN-GW| R3 | CSN | R5 | | ---- | |R8 /--|------|----| |-----|Home| | ---- / | | visited| | NSP| | |BS|/ | | NSP | | | | ---- | |---------| | | | NAP | \ |----| ------------------- \---| / | | / | (--|------/----) |R4 ( ) | ( ASP network ) --------- ( or Internet ) | ASN | ( ) --------- (----------) Figure 2: WiMAX Network reference model Three different types of ASN realizations called profiles are defined by the architecture. ASNs of profile types A and C include BS' and ASN-gateway(s) which are connected to each other via an R6 interface. An ASN of profile type B is one in which the functionality of the BS and other ASN functions are merged together. No ASN-GW is specifically defined in a profile B ASN. However all the functions of an ASN such as the MIP4 FA, AAA, AR exist within the scope of an ASN. The absence of the R6 interface is also a profile B specific characteristic. The MS at the IPv6 layer is associated with the AR in the ASN. The AR may be a function of the ASN-GW in the case of profiles A and C and is a function in the ASN in the case of profile B. When the BS and the AR are separate entities and linked via the R6 interface, IPv6 packets between the BS and the AR are carried over a Patil, et al. Expires April 17, 2007 [Page 7] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 GRE tunnel. The granularity of the GRE tunnel can be on a per flow basis, per MS basis or on a BS basis. The protocol stack in WiMAX for IPv6 is shown below: |-------| | App |- - - - - - - - - - - - - - - - - - - - - - - -(to app peer) | | |-------| /------ ------- | | / IPv6 | | | | IPv6 |- - - - - - - - - - - - - - - - / | | |--> | | --------------- -------/ | | IPv6| |-------| | \Relay/ | | | |- - - | | | | | \ / | | GRE | | | | | | | \ /GRE | - | | | | | | |- - - | |-----| |------| | | | | IPv6CS| |IPv6CS | IP | - | IP | | | | | ..... | |...... |-----| |------|--------| |-----| | MAC | | MAC | L2 | - | L2 | L2 |- - - | L2 | |-------| |------ |-----| |----- |--------| |-----| | PHY |- - - | PHY | L1 | - | L1 | L1 |- - - | L1 | -------- --------------- ----------------- ------- MS BS AR/ASN-GW CSN Rtr Figure 3: WiMAX protocol stack As can be seen from the protocol stack description, the IPv6 end- points are constituted in the MS and the AR. The BS provides lower layer connectivity for the IPv6 link. Patil, et al. Expires April 17, 2007 [Page 8] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 6. IPv6 link in WiMAX The MS and the AR are connected via a combination of : 1. The transport connection which is identified by a Connection Identifier (CID) over the air interface, i.e the MS and BS and, 2. A GRE tunnel between the BS and AR which transports the IPv6 packets From an IPv6 perspective the MS and the AR are connected by a point- to-point link. The transport connection over the air interface and the GRE tunnel between the BS and AR create a tunnel at the layer below IPv6. Each link has only an MS and an AR. Each MS belongs to a different link. No two MSs belong to the same link. A different prefix should be assigned to a different link. This link is fully consistent with a standard IP link, without exception and conforms with the definition of a point-to-point link in RFC2461 [RFC2461]. 6.1. IPv6 link establishment The mobile station performs initial network entry as specified in 802.16e [Ref80216]. On succesful completion of the network entry procedure the ASN gateway/AR triggers the establishment of the initial service flow (ISF) for IPv6 towards the MS. The ISF is a GRE tunnel between the ASN-GW/AR and the BS. The BS in turn requests the MS to establish a transport connection over the air interface. The end result is a transport connection over the air interface for carrying IPv6 packets and a GRE tunnel between the BS and AR for relaying the IPv6 packets. On succesful completion of the establishment of the ISF, IPv6 packets can be sent and received between the MS and AR. The ISF enables the MS to communicate with the AR for host configuration procedures. After the establishment of the ISF, the AR can send a router advertisement to the MS. An MS can establish multiple service flows with different QoS characteristics. The ISF can be considered as the primary service flow. 6.2. Maximum transmission unit The WiMAX forum [WMF] has specified the SDU size as 1522 octets. Hence the IPv6 path MTU can be 1500 octets. However because of the overhead of the GRE tunnel used to transport IPv6 packets between the BS and AR and the 6 byte MAC header over the air interface, using a value of 1500 would result in fragmentation of packets. It is recommended that the default MTU for IPv6 be set to 1400 octets for the MS. Note that the 1522 octet specification is a WiMAX forum specification and not the size of the SDU that can be transmitted over 802.16d/e, which is higher. RFC2461 [RFC2461] recommends that Patil, et al. Expires April 17, 2007 [Page 9] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 IPv6 nodes implement Path MTU discovery. In such cases the default value can be over-ridden. Additionally if the 802.16d/e MAC layer can provide an indication of the MTU size to be used, the MS can use that as the default MTU. Patil, et al. Expires April 17, 2007 [Page 10] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 7. IPv6 prefix assignment Each MS can be considered to be on a separate subnet as a result of the point-to-point cconnection. While the MS can establish multiple service flows that map to corresponding transport connections over the air interface, the ISF and any other service flows established for IPv6 traffic should be treated as a single subnet. A CPE type of device which serves multiple IPv6 hosts, may be the end point of the connection. Hence one or more /64 prefixes should be assigned to an ISF. The prefixes are advertised with the on-link (L-bit) flag set so that MSs may not make any asumption about the existence of on-link neighbors. Patil, et al. Expires April 17, 2007 [Page 11] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 8. Router Discovery 8.1. Router Solictation On completion of the establishment of the IPv6 ISF, the MS may send a router solicitation message to solicit a Router Advertisement message from the AR to acquire necessary information as specified in RFC2461 [RFC2461]. An MS that is network attached may also send router solicitations at any time. 8.2. Router Advertisement The AR should send a number of router advertisements as soon as the IPv6 ISF is established to the MS. The AR may send unsolicited router advertisements periodically as specified in RFC2461 [RFC2461]. However to conserve the battery lifetime of hosts and to conserve radio resources over the air interface, unsolicited router advertisement transmission are not recommended. 8.3. Router lifetime and periodic router advertisements The router lifetime should be set to a large value, preferably in hours. 802.16d/e hosts have the capability to transition to an Idle mode in which case the radio link between the BS and MS is torn down. Paging is required in case the network needs to deliver packets to the MS. In order to avoid waking a mobile which is in Idle mode and consuming resources on the air interface, the interval between periodic router advertisements should be set quite high. The MaxRtrAdvInterval should be configurable to a value which is greater than 1800 seconds. Patil, et al. Expires April 17, 2007 [Page 12] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 9. IPv6 addressing for hosts The addressing scheme for IPv6 hosts in WiMAX follows the IETFs recommendation for hosts specified in RFC 4294. The IPv6 node requirements RFC RFC4294 [RFC4294] specifies a set of RFCs that are applicable for addressing. 9.1. Interface Identifier The MS has a 48-bit MAC address as specified in 802.16e [802.16e]. This MAC address is used to generate the 64 bit interface identifier which is used by the MS for address autoconfiguration. The IID is generated by the MS as specified in RFC2464 [RFC2464]. For addresses that are based on privacy extensions, the MS may generate random IIDs as specified in RFC3041 [RFC3041]. 9.2. Duplicate address detection DAD is performed as per RFC2461 [RFC2461] and, RFC2462 [RFC2462]. 9.3. Stateless address autoconfiguration If the L-bit and A-bit in the prefix information option (PIO) are set the MS performs stateless address autoconfiguration as per RFC 2461, 2462. The AR in the ASN is the default router that advertises a unique /64 prefix (or prefixes) that is used by the MS to configure an address. 9.4. Stateful address autoconfiguration The Stateful Address Autoconfiguration is invoked if the M-flag is set in the Router Advertisement. Obtaining the IPv6 address through stateful address autoconfiguration method is specified in the RFC3315 [RFC3315]. Patil, et al. Expires April 17, 2007 [Page 13] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 10. IANA Considerations This draft does not require any actions from IANA. Patil, et al. Expires April 17, 2007 [Page 14] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 11. Security Considerations This document does not introduce any new vulnerabilities to IPv6 specifications or operation as a result of the 802.16d/e air interface or the WiMAX network architecture. Patil, et al. Expires April 17, 2007 [Page 15] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 12. Acknowledgments TBD. Patil, et al. Expires April 17, 2007 [Page 16] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997, . [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998, . [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998, . [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, December 1998, . [RFC3041] Narten, T. and R. Draves, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 3041, January 2001, . [RFC3314] Wasserman, Ed., M., "Recommendations for IPv6 in Third Generation Partnership Project (3GPP) Standards", RFC 3314, September 2002, . [RFC3315] Droms, Ed., R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003, . [RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor Discovery (ND) Trust Models and Threats", RFC 3756, May 2004, . [RFC4294] Loughney, Ed., J., "IPv6 Node requirements", RFC 4294, April 2006, . [RFC4921] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4921, February 2006, . Patil, et al. Expires April 17, 2007 [Page 17] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 13.2. Informative References [802.16e] "IEEE Std 802.16e: IEEE Standard for Local and metropolitan area networks, Amendment for Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands", October 2005. [WMF] "http://www.wimaxforum.org". [WiMAXArch] "WiMAX End-to-End Network Systems Architecture http://www.wimaxforum.org/technology/documents", August 2006. Patil, et al. Expires April 17, 2007 [Page 18] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 Authors' Addresses Basavaraj Patil Nokia 6000 Connection Drive Irving, TX 75039 USA Email: basavaraj.patil@nokia.com Frank Xia Huawei USA 1700 Alma Dr. Suite 100 Plano, TX 75075 Email: xiayangsong@huawei.com Behcet Sarikaya Huawei USA 1700 Alma Dr. Suite 100 Plano, TX 75075 Email: sarikaya@ieee.org Syam Madanapalli LogicaCMG 125 Yemlur P.O. Off Airport Road Bangalore, India 560037 Email: smadanapalli@gmail.com JinHyeock Choi Samsung AIT Networking Technology Lab P.O.Box 111 Suwon, Korea 440-600 Email: jinchoe@samsung.com Patil, et al. Expires April 17, 2007 [Page 19] Internet-Draft IPv6 over IPv6 CS in WiMAX October 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). 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. 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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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Patil, et al. Expires April 17, 2007 [Page 20]