Network Working Group Basavaraj Patil Internet-Draft Nokia Intended status: Standards Track Frank Xia Expires: September 6, 2007 Behcet Sarikaya Huawei USA JH. Choi Samsung AIT Syam Madanapalli LogicaCMG March 5, 2007 IPv6 Over the IP Specific part of the Packet Convergence sublayer in 802.16 Networks draft-ietf-16ng-ipv6-over-ipv6cs-08 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 September 6, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract IEEE Std 802.16 is an Air Interface for Fixed and Mobile Broadband Patil, et al. Expires September 6, 2007 [Page 1] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Wireless Access Systems. The 802.16 specification includes several service specific convergence sublayers (CS) as part of the MAC (Medium Access Control) layer which are used by upper layer protocols. The ATM CS and Packet CS are the two main service specific convergence sublayers and these are a part of the 802.16 MAC to which the upper layers interface. The packet CS is used for transport for all packet-based protocols such as Internet Protocol (IP), IEEE Std. 802.3 (Ethernet) and, IEEE Std 802.1Q (VLAN). The IP specific part of the Packet CS enables transport of IPv4 and IPv6 packets directly over the MAC. This document specifies the addressing and operation of IPv6 over the IP specific part of the packet CS for hosts served by a network that utilizes the IEEE Std 802.16 air interface. It recommends the assignment of a unique prefix (or prefixes) to each host and allows the host to use multiple identifiers within that prefix, including support for randomly generated interface identifiers. Patil, et al. Expires September 6, 2007 [Page 2] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Table of Contents 1. Conventions used in this document . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IEEE 802.16 convergence sublayer support for IPv6 . . . . . . 5 4.1. IPv6 encapsulation over the IP CS of the MAC . . . . . . . 7 5. Generic network architecture using the 802.16 air interface . 9 6. IPv6 link . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. IPv6 link in 802.16 . . . . . . . . . . . . . . . . . . . 10 6.2. IPv6 link establishment in 802.16 . . . . . . . . . . . . 11 6.3. Maximum transmission unit in 802.16 . . . . . . . . . . . 12 7. IPv6 prefix assignment . . . . . . . . . . . . . . . . . . . . 12 8. Router Discovery . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Router Solicitation . . . . . . . . . . . . . . . . . . . 12 8.2. Router Advertisement . . . . . . . . . . . . . . . . . . . 13 8.3. Router lifetime and periodic router advertisements . . . . 13 9. IPv6 addressing for hosts . . . . . . . . . . . . . . . . . . 13 9.1. Interface Identifier . . . . . . . . . . . . . . . . . . . 13 9.2. Duplicate address detection . . . . . . . . . . . . . . . 14 9.3. Stateless address autoconfiguration . . . . . . . . . . . 14 9.4. Stateful address autoconfiguration . . . . . . . . . . . . 14 10. Multicast Listener Discovery . . . . . . . . . . . . . . . . . 14 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 12. Security Considerations . . . . . . . . . . . . . . . . . . . 15 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 14.1. Normative References . . . . . . . . . . . . . . . . . . . 15 14.2. Informative References . . . . . . . . . . . . . . . . . . 16 Appendix A. WiMAX network architecture and IPv6 support . . . . . 16 Appendix B. IPv6 link in WiMAX . . . . . . . . . . . . . . . . . 18 Appendix C. IPv6 link establishment in WiMAX . . . . . . . . . . 19 Appendix D. Maximum transmission unit in WiMAX . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . . . 21 Patil, et al. Expires September 6, 2007 [Page 3] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 1. 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 RFC 2119 [RFC2119]. 2. Introduction IEEE 802.16e is an air interface for fixed and mobile broadband wireless access systems. Orthogonal Frequency Division Multiplexing (OFDM) is the basis of the air interface. The standard specifies the air interface, including the medium access control (MAC) layer and multiple physical layer (PHY) specifications. It can be deployed in licensed as well as unlicensed spectrum. While the PHY and MAC are specified in IEEE 802.16, the details of IPv4 and IPv6 operation over the air interface are not included. This document specifies the operation of IPv6 over the IEEE 802.16 air interface. IPv6 packets can be carried over the IEEE Std 802.16 specified air interface via : 1. the IP specific part of the Packet CS or, 2. the 802.3 specific part of the Packet CS or, 3. the 802.1Q specific part of the Packet CS. The 802.16 [802.16] specification includes the Phy and MAC details. The convergence sublayers are a part of the MAC. This document specifies IPv6 from the perspective of the transmission of IPv6 over the IP specific part of the packet convergence sublayer. The mobile station/host is attached to an access router via a base station (BS). The host and the BS are connected via the IEEE Std 802.16 air interface at the link and physical layers. The IPv6 link from the MS terminates at an access router which may be a part of the BS or an entity beyond the BS. The base station is a layer 2 entity (from the perspective of the IPv6 link between the MS and AR) and relays the IPv6 packets between the AR and the host via a point-to- point connection over the air interface. 3. Terminology The terminology in this document is based on the definitions in [PSDOC]. Patil, et al. Expires September 6, 2007 [Page 4] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 4. IEEE 802.16 convergence sublayer support for IPv6 The IEEE 802.16 MAC specifies two main service specific convergence sublayers: 1. ATM Convergence sublayer 2. Packet Convergence sublayer The Packet CS is used for the transport of packet based protocols which include: 1. IEEE Std 802.3(Ethernet) 2. IEEE Std 802.1Q(VLAN) 3. Internet Protocol (IPv4 and IPv6) The service specific CS resides on top of the MAC Common Part Sublayer (CPS). The service specific CS is responsible for: o accepting packets (PDUs) from the upper layer, o performing classification of the packet/PDU based on a set of classifiers that are defined which are service specific, o delivering the CS PDU to the appropriate service flow and transport connection and, o receiving PDUs from the peer entity. Payload header suppression (PHS) is also a function of the CS but is optional. The figure below shows the concept of the service specific CS in relation to the MAC: -----------------------------\ | ATM CS | Packet CS | \ ----------------------------- \ | MAC Common Part Sublayer | \ | (Ranging, scheduling, etc)| 802.16 MAC ----------------------------- / | Security | / |(Auth, encryption,key mgmt)| / -----------------------------/ | PHY | ----------------------------- Figure 1: The 802.16 MAC Patil, et al. Expires September 6, 2007 [Page 5] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Classifiers for each of the specific upper-layer protocols, i.e Ethernet, VLAN and IP, are defined in the IEEE 802.16 specification, which enable the packets from the upper layer to be processed by the appropriate service specific part of the packet CS. IPv6 can be transported directly over the IP specific part of the packet CS or over 802.3/Ethernet (which in turn is handled by the Ethernet specific part of the packet CS) or over 802.1Q (which is handled by the 802.1Q specific part of the packet CS). IPv6 over the IP specific part of the packet CS SHOULD be the default method for IPv6 packet transmission. IPv4 packets also are transported over the IP specific part of the packet CS. The classifiers enable the differntiation of IPv4 and IPv6 packets and mapping to specific transport connections over the air-interface. The figure below shows the options for IPv6 transport over the packet CS of 802.16: ----------------- ----------------- | IPv6 | | IPv6 | ---------------- |---------------| |----------- | | IPv6 | | Ethernet | | 802.1Q | |--------------| |---------------| |----------- | | IP Specific | | 802.3 specific| |802.1Q specific| |part of Pkt CS| |part of Pkt CS | |part of Pkt CS | |..............| |...............| |...............| | MAC | | MAC | | MAC | |--------------| |---------------| |---------------| | PHY | | PHY | | PHY | ---------------- ----------------- ----------------- (1) IPv6 over (2) IPv6 over (3) IPv6 over IP Specific part 802.3/Ethernet 802.1Q of Packet CS Figure 2: IPv6 over IP, 802.3 and 802.1Q specific parts of the Packet CS The scope of this document is limited to IPv6 operation over the IP specific part of the Packet CS only. IPv4 over the IP specific part of the packet CS is specified in [IPv4CS]. It should be noted that immediately after ranging (802.16 air interface procedure), the MS and BS exchange their capability negotiation via REG-REQ (Registration Request) and REG-RSP (Registration Response) 802.16 MAC messages. These management frames negotiate parameters such as the Patil, et al. Expires September 6, 2007 [Page 6] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Convergence Sublayer support. By default, Packet, IPv4 and 802.3/ Ethernet are supported. IPv6 via the Packet CS is supported by the MS and the BS only when the IPv6 support bit in the capability negotiation messages (REG-REQ and REG-RSP) implying such support is indicated in the parameter "Classification/PHS options and SDU (Service Data Unit) encapsulation support" (Refer to [802.16]). Additionally during the establishment of the transport connection for transporting IPv6 packets, the DSA-REQ (Dynamic Service Addition) and DSA-RSP messages between the BS and MS indicate via the CS- Specification TLV the CS that the connection being setup shall use. When the IPv6 packet is preceded by the 802.16 six byte MAC header there is no specific indication in the MAC header itself about the payload type. The processing of the packet is based entirely on the classifiers. Based on the classification rules, the MAC layer selects an appropriate transport connection for the transmission of the packet. An IPv6 packet is transported over a transport connection that is specifically established for carrying such packets. Transmission of IPv6 as explained above is possible via multiple methods, i.e, via the IP specific part of the packet CS or via Ethernet or 802.1Q interfaces. The choice of which method to use is implementation specific. When IPv6 is carried via the IP convergence sublayer, this specification SHOULD be followd. In order to ensure interoperability the BS SHOULD support the IP specific part of the packet CS and the Ethernet specific part of the packet CS for IPv6 transport. Hosts which may implement one or the other method for transmission would be assured of the ability to establish a transport connection that would enable the transport of IPv6 packets. Inability to negotiate a common convergence sublayer for the transport connection between the MS and BS will result in failure to setup the transport connection and thereby render the host unable to send and receive IPv6 packets. In the case of a host which implements more than one method of transporting IPv6 packets, the choice of which method to use (i.e IPv6 over the IP specific part of the packet CS or IPv6 over 802.3 or, IPv6 over 802.1Q) is implementation specific. The host and the BS SHOULD support the transmission of IPv6 over the IP specific part of the packet convergence sublayer. The default method for IPv6 packet transmission over 802.16 should be via the packet CS. 4.1. IPv6 encapsulation over the IP CS of the MAC The IPv6 payload when carried over the IP specific part of the Packet CS is encapsulated by the 6 byte 802.16 generic MAC header. The format of the IPv6 packet encapsulated by the generic MAC header is shown in the figure below. The format of the 6 byte MAC header is described in the [802.16] specification. The CRC (cyclic redundancy Patil, et al. Expires September 6, 2007 [Page 7] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 check) is optional. It should be noted that the actual MAC address is not included in the MAC header. ---------/ /----------- | MAC SDU | --------/ /------------ || || MSB \/ LSB --------------------------------------------------------- | Generic MAC header| IPv6 Payload | CRC | --------------------------------------------------------- Figure 3: IPv6 encapsulation For transmission of IPv6 packets via the IP specific part of the Packet CS of 802.16, the IPv6 layer interfaces with the 802.16 MAC directly. The IPv6 layer delivers the IPv6 packet to the Packet CS of the 802.16. The packet CS defines a set of classifiers that are used to determine how to handle the packet. The IP classifiers that are used at the MAC operate on the fields of the IP header and the transport protocol and these include the IP Traffic class, Next header field, Masked IP source and destination addresses and, Protocol source and destination port ranges. Next header in this case refers to the last header of the IP header chain. Using the classifiers, the MAC maps an upper layer packet to a specific service flow and transport connection to be used. The MAC encapsulates the IPv6 packet in the 6 byte MAC header (MAC SDU) and transmits it. The figure below shows the operation on the downlink, i.e the transmission from the BS to the host. The reverse is applicable for the uplink transmission. Patil, et al. Expires September 6, 2007 [Page 8] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 ----------- ---------- | IPv6 Pkt| |IPv6 Pkt| ----------- ---------- | | /|\ | | | --[SAP]--------------------- ---------[SAP]-------- ||-| |----------| | | /|\ | || \ / 0---->[CID1] | | --- |-------- | || Downlink 0\/-->[CID2] | | |Reconstruct| | || classifiers0/\-->[....] | | | (undo PHS)| | || 0---->[CIDn] | | --- ------- | ||--------------| | | /|\ | | | | | | | {SDU, CID,..} | | {SDU, CID,..} | | | | | /|\ | | v | | | | ------[SAP]----------------- |-------[SAP]--------- | 802.16 MAC CPS |------>| 802.16 MAC CPS | ---------------------------- ---------------------- Figure 4: IPv6 packet transmission: Downlink 5. Generic network architecture using the 802.16 air interface In a network that utilizes the 802.16 air interface the host/MS is attached to an IPv6 access router (AR) in the network. The BS is a layer 2 entity only. The AR can be an integral part of the BS or the AR could be an entity beyond the BS within the access network. IPv6 packets between the MS and BS are carried over a point-to-point transport connection which has a unique connection identifier (CID). The transport connection is a MAC layer link between the MS and the BS. The figures below describe the possible network architectures and are generic in nature. More esoteric architectures are possible but not considered in the scope of this document. Option A: +-----+ CID1 +--------------+ | MS1 |------------/| BS/AR |-----[Internet] +-----+ / +--------------+ . /---/ . CIDn +-----+ / | MSn |---/ +-----+ Patil, et al. Expires September 6, 2007 [Page 9] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Figure 5: The IPv6 AR as an integral part of the BS Option B: +-----+ CID1 +-----+ +-----------+ | MS1 |----------/| BS1 |----------| AR |-----[Internet] +-----+ / +-----+ +-----------+ . / ____________ . CIDn / ()__________() +-----+ / L2 Tunnel | MSn |-----/ +-----+ Figure 6: The IPv6 AR is separate from the BS The above network models serve as examples and are shown to illustrate the point to point link between the MS and the AR. 6. IPv6 link RFC 2461 defines link as a communication facility or medium over which nodes can communicate at the link layer, i.e., the layer immediately below IP [RFC2461]. A link is bounded by routers that decrement the Hop limit field in the IPv6 header. When an MS moves within a link, it can keep using its IP addresses. This is a layer 3 definition and note that the definition is not identical with the definition of the term '(L2) link' in IEEE 802 standards. 6.1. IPv6 link in 802.16 In 802.16, the Transport Connection between an MS and a BS is used to transport user data, i.e. IPv6 packets in this case. A Transport Connection is represented by a CID (Connection Identifier) and multiple Transport Connections can exist between an MS and BS. When an AR and a BS are collocated, the collection of Transport Connections to an MS is defined as a single link. When an AR and a BS are separated, it is recommended that a tunnel is established between the AR and a BS whose granuality is no greater than 'per MS' or 'per service flow' ( An MS can have multiple service flows which are identified by a service flow ID). Then the tunnel(s) for an MS, in combination with the MS's Transport connections, forms a single point-to-point link. Patil, et al. Expires September 6, 2007 [Page 10] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 The collection of service flows (tunnels) to an MS is defined as a single link. Each link has only an MS and an AR. Each MS belongs to a different link. A different prefix should be assigned to each unique 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]. Hence the point-to-point link model for IPv6 operation over the IP specific part of the Packet CS in 802.16 SHOULD be used. A unique IPv6 prefix(es) per link (MS/host) MUST be assigned. 6.2. IPv6 link establishment in 802.16 In order to enable the sending and receiving of IPv6 packets between the MS and the AR, the link between the MS and the AR via the BS needs to be established. This section illustrates the link establishment procedure. The MS goes through the network entry procedure as specified by 802.16. A high level description of the network entry procedure is as follows: 1. MS performs initial ranging with the BS. Ranging is a process by which an MS becomes time aligned with the BS. The MS is synchronized with the BS at the succesful completion of ranging and is ready to setup a connection. 2. MS and BS perform capability exchange as per 802.16 procedures. The CS capability parameter indicates which classification/PHS options and SDU encapsulation the MS supports. By default, Packet, IPv4 and 802.3/Ethernet shall be supported, thus absence of this parameter in REG-REQ (802.16 message) means that named options are supported by the MS/SS. Support for IPv6 over the IP specific part of the packet CS is indicated by Bit#2 of the CS capability parameter (Refer to [802.16]). 3. The MS progresses to an authentication phase. Authentication is based on PKMv2 as defined in the IEEE Std 802.16 specification. 4. On succesful completion of authentication, the MS performs 802.16 registration with the network. 5. The MS MUST request the establishment of a service flow for IPv6 packets over the IP specific part of the Packet CS. The service flow MAY also be triggered by the network as a result of pre- provisioning. The service flow establishes a link between the MS and the AR over which IPv6 packets can be sent and received. 6. The AR and MS should send router advertisements and solicitations as specified in Neighbor discovery, RFC2461 [RFC2461]. The above flow does not show the actual 802.16 messages that are used for ranging, capability exchange or service flow establishment. Details of these are in [802.16]. Patil, et al. Expires September 6, 2007 [Page 11] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 6.3. Maximum transmission unit in 802.16 The 802.16 MAC PDU (Protocol Data Unit) is composed by a 6 byte header followed by an optional payload and an optional CRC covering the header and the payload. The length of the PDU is indicated by the Len parameter in the Generic MAC Header. The Len parameter has a size of 11 bits. Hence the total PDU size is 2048 bytes. The IPv6 payload can be a max value of 2038 bytes ( Total PDU size minus (MAC Header + CRC)). The Max value of the IPv6 MTU for 802.16 is 2038 bytes and the minimum value of 1280 bytes. The default MTU for IPv6 over 802.16 SHOULD be the same as specified in RFC2460 which is 1500 octets. RFC2461 defines an MTU option that an AR can advertise to an MN. If an AR advertises an MTU via the RA MTU option, the MN SHOULD use the MTU from the RA. 7. IPv6 prefix assignment The MS and the AR are connected via a point-to-point connection at the IPv6 layer. Hence each MS can be considered to be on a separate subnet. A CPE (Customer Premise Equipment) 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 a link. The prefixes are advertised with the on-link (L-bit) flag set as specified in RFC2461 [RFC2461]. The size and number of the prefixes is a configuration issue. Also, prefix delegation MAY be used to provide additional prefixes for a router connected over 802.16. The other properties of the prefixes are also dealt via configuration. 8. Router Discovery 8.1. Router Solicitation On completion of the establishment of the IPv6 link, the MS may send a router solicitation message to solicit a Router Advertisement message from the AR to acquire necessary information as per RFC2461. An MS that is network attached may also send router solicitations at any time as per RFC2461. Movement detection at the IP layer of an MS in many cases is based on receiving periodic router advertisements. An MS may also detect changes in its attachment via link triggers or other means. The MS can act on such triggers by sending router solicitations. The router solicitation is sent over the IPv6 link that has been previously established. The MS sends router solicitations to the all-routers multicast address. It is carried over the point-to-point link to the AR via the BS. The MS does not need to be aware of the link-local address of the AR in order to send a router solicitation at any time. Patil, et al. Expires September 6, 2007 [Page 12] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 8.2. Router Advertisement The AR should send a number (configurable value) of router advertisements as soon as the IPv6 link is established, to the MS. The AR sends unsolicited router advertisements periodically as per RFC2461. The interval between periodic router advertisements is however greater than the specification in RFC2461 and is discussed in the following section. 8.3. Router lifetime and periodic router advertisements The router lifetime SHOULD be set to a large value, preferably in hours. This document over-rides the specification for the value of the router lifetime in Neighbor Discovery for IP Version 6 (IPv6) RFC2461 [RFC2461]. The AdvDefaultLifetime in the router advertisement MUST be either zero or between MaxRtrAdvInterval and 43200 seconds. The default value is 2 * MaxRtrAdvInterval. 802.16 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 value specified in this document over-rides the recommendation in Neighbor Discovery for IP Version 6 (IPv6) RFC2461 [RFC2461]. The MaxRtrAdvInterval MUST be no less than 4 seconds and no greater than 21600 seconds. The default value for MaxRtrAdvInterval is 10800 seconds. 9. IPv6 addressing for hosts The addressing scheme for IPv6 hosts in 802.16 network follows the IETFs recommendation for hosts specified in IPv6 Node Requirement, RFC 4294. The IPv6 node requirements RFC4294 [RFC4294] specifies a set of RFCs that are applicable for addressing and the same is applicable for hosts that use 802.16 as the link layer for transporting IPv6 packets. 9.1. Interface Identifier The MS has a 48-bit MAC address as specified in 802.16 [802.16]. This MAC address MUST be used if EUI-64 based interface identifier is needed for autoconfiguration, IP Version 6 Addressing Architecture RFC4291 [RFC4291]. As in other links that support IPv6, EUI-64 based interface identifiers are not mandatory and other mechanisms, such as random interface identifiers, Privacy Extensions for Stateless Patil, et al. Expires September 6, 2007 [Page 13] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Address Autoconfiguration in IPv6 RFC3041 [RFC3041] MAY also be used. 9.2. Duplicate address detection DAD SHOULD be performed as per Neighbor Discovery for IP Version 6,RFC2461 [RFC2461] and, IPv6 Stateless Address Autoconfiguration, RFC2462 [RFC2462]. It MAY be redundant to perform DAD on a global unicast address that is configured using the EUI-64 or generated as per RFC3041 [RFC3041] for the interface as part of the IPv6 stateless address autoconfiguration protocol RFC2462 [RFC2462] as long as the following two conditions are met: 1. The prefixes advertised through the router advertisement messages by the access router terminating the 802.16 IPv6 link is unique to that link. 2. The access router terminating the 802.16 IPv6 link does not autoconfigure any IPv6 global unicast addresses from the prefix that it advertises. 9.3. Stateless address autoconfiguration If the A-bit in the prefix information option (PIO) is set, the MS SHOULD perform stateless address autoconfiguration as per RFC 2461, 2462. The AR is the default router that advertises a unique 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 RFC3315 [RFC3315]. The MS MUST obtain an address via the stateful address autoconfiguration mechanism when the M-flag is set in the router advertisement. 10. Multicast Listener Discovery Multicast Listener Discovery Version 2(MLDv2) for IPv6 RFC3810 [RFC3810] SHOULD be supported as specified by the hosts and routers attached to each other via an 802.16 link. The access router which has hosts attached to it via a Point-to-point link over an 802.16 SHOULD not send periodic queries if the host is in idle/dormant mode. The AR can obtain information about the state of a host from the paging controller in the network. Patil, et al. Expires September 6, 2007 [Page 14] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 11. IANA Considerations This draft does not require any actions from IANA. 12. Security Considerations This document does not introduce any new vulnerabilities to IPv6 specifications or operation. The security of the 802.16 air interface is the subject of [802.16]. In addition, the security issues of the network architecture spanning beyond the 802.16 base stations is the subject of the documents defining such architectures, such as WiMAX Network Architecture [WiMAXArch]. 13. Acknowledgments The authors would like to acknowledge the contributions of the 16NG working group chairs Soohong Daniel Park and Gabriel Montenegro as well as Jari Arkko, Jonne Soininen, Max Riegel, Prakash Iyer, DJ Johnston, Dave Thaler, Bruno Sousa, Alexandru Petrescu, Margaret Wasserman and Pekka Savola for their review and comments. 14. References 14.1. Normative References [802.16] "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. [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, . [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004, . Patil, et al. Expires September 6, 2007 [Page 15] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006, . 14.2. Informative References [IPv4CS] Madanapalli, S. and S. Park, "Transmission of IPv4 packets over 802.16's IP Convergence Sublayer", February 2007, . [PSDOC] Jee, J., Madanapalli, S., Montenegro, G., Riegel, M., Mandin, J., and S. Park, "IP over 802.16 Problem Statement and Goals", October 2006, . [RFC3041] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", August 2006, . [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, . [RFC4294] Loughney, Ed., J., "IPv6 Node requirements", RFC 4294, April 2006, . [WMF] "http://www.wimaxforum.org". [WiMAXArch] "WiMAX End-to-End Network Systems Architecture http://www.wimaxforum.org/technology/documents", August 2006. Appendix A. WiMAX network architecture and IPv6 support The WiMAX (Worldwide Interoperability for Microwave Access) forum [WMF] has defined a network architecture in which the air interface is based on the IEEE 802.16 standard. The addressing and operation of IPv6 described in this document is applicable to the WiMAX network as well. 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 Patil, et al. Expires September 6, 2007 [Page 16] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 functions such as AAA, Mobile IP Foreign agent, Paging controller, Location Register etc. 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. The term ASN is specific to the WiMAX network architecture. 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 7: 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) (ASN-GW) 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. 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 GRE tunnel. The granularity of the GRE tunnel should be on a per MS basis or on a per service flow basis (an MS can have multiple service flows, each of Patil, et al. Expires September 6, 2007 [Page 17] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 which are identified uniquely by a service flow ID). 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 8: 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. Appendix B. IPv6 link in WiMAX WiMAX is an example of a network based on the IEEE Std 802.16 air interface. This section describes the IPv6 link in the context of a WiMAX network. 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 combination of transport connection over the air interface and the GRE tunnel between the BS and AR creates a (point- Patil, et al. Expires September 6, 2007 [Page 18] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 to-point) tunnel at the layer below IPv6. The collection of service flows (tunnels) to an MS is defined as a single link. 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 each unique 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]. Appendix C. IPv6 link establishment in WiMAX The mobile station performs initial network entry as specified in 802.16. 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. The ASN-GW/ AR treats each ISF, along with the other service flows to the same MS, as a unique link which is managed as a (virtual) interface. Appendix D. Maximum transmission unit in WiMAX The WiMAX forum [WMF] has specified the Max 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 in WiMAX networks. Note that the 1522 octet specification is a WiMAX forum specification and not the size of the SDU that can be transmitted over 802.16, which has a higher limit. Patil, et al. Expires September 6, 2007 [Page 19] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 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 JinHyeock Choi Samsung AIT Networking Technology Lab P.O.Box 111 Suwon, Korea 440-600 Email: jinchoe@samsung.com Syam Madanapalli LogicaCMG 125 Yemlur P.O. Off Airport Road Bangalore, India 560037 Email: smadanapalli@gmail.com Patil, et al. Expires September 6, 2007 [Page 20] Internet-Draft IPv6 over Packet CS in 802.16 March 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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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 September 6, 2007 [Page 21]