16ng Working Group S. Madanapalli Internet-Draft LogicaCMG Intended status: Standards Track Soohong D. Park Expires: August 11, 2007 Samsung Electronics February 7, 2007 Transmission of IPv4 packets over 802.16's IP Convergence Sublayer draft-madanapalli-16ng-ipv4-over-802-dot-16-ipcs-00.txt 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 August 11, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract IEEE 802.16 is an air interface specification for wireless broadband access. IEEE has specified several service specific convergence sublayers (CS) for 802.16 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 which the upper layers interface to. The packet CS is used for transport for all packet-based protocols such as Internet Protocol (IP), IEEE Madanapalli & Park Expires August 11, 2007 [Page 1] Internet-Draft IPv4 over 802.16's IP CS February 2007 Std. 802.3 (Ethernet) and, IEEE Std 802.1Q (VLAN). The IP specific part of the Packet CS enables transport of IPv4 packets directly over the 802.16 MAC. This document specifies the frame format, the Maximum Transmission Unit (MTU) and address assignment procedures for transmitting Pv4 packets over IP Convergence Sublayer (IPCS) of IEEE 802.16. This document describes on how to deal with Address Resolution Protocol (ARP) and Mapping of multicast IP address to MAC address. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Typical Network Architecture for IPv4 over 802.16 . . . . . . 3 4. Frame Format for IPv4 Packets . . . . . . . . . . . . . . . . 4 5. Maximum Transmission Unit . . . . . . . . . . . . . . . . . . 5 6. IPv4 Address Assignment . . . . . . . . . . . . . . . . . . . 6 7. Address Resolution Protocol . . . . . . . . . . . . . . . . . 6 8. IP Multicast Address Mapping . . . . . . . . . . . . . . . . . 6 9. Sending and Receiving IPv4 Packets . . . . . . . . . . . . . . 6 10. Security Considerations . . . . . . . . . . . . . . . . . . . 7 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 13.1. Normative References . . . . . . . . . . . . . . . . . . 8 13.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Madanapalli & Park Expires August 11, 2007 [Page 2] Internet-Draft IPv4 over 802.16's IP CS February 2007 1. Introduction 802.16 [6] is a connection oriented access technology for the last mile without bi-directional native multicast support. 802.16 has only downlink multicast support and there is no mechanisms defined for mobile stations to be able to send multicast packets that can be mapped to downlink multicast connection. And also 802.16 MAC does not use the Source and Destination MAC addresses, instead it uses the Connection Identifiers (CIDs), which are assigned dynamically while setting up the MAC connections, for transmitting the 802.16 frames between a Mobile Station and a Base Station. This document specifies a method for encapsulating and transmitting IPv4 [2] and Address Resolution Protocol (ARP) packets over IP CS of IEEE 802.16. This document also specifies the MTU and address assignment method for the 802.16 based networks using IPCS. As the 802.16 MAC does not use the source and destination MAC addresses for the frame transmission, this document recommends avoiding ARP and Mapping of multicast IP address to MAC address, and recommends always assigning a default gateway for the mobile stations. 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 [1]. 2. Terminology The terminology in this document is based on the definitions in [10], in addition to the ones specified in this section. Access Router (AR): An entity that performs an IP routing function to provide IP connectivity for Mobile Stations. In WiMAX Networks, the AR is an Access Service Network Gateway. 3. Typical Network Architecture for IPv4 over 802.16 In a network that utilizes the 802.16 air interface the MS is attached to an Access Router (AR) through a Base Station (BS), a layer 2 entity. The AR can be an integral part of the BS or the AR could be an entity beyond the BS within the access network. IPv4 packets between the MS and BS are carried over a point-to-point MAC transport connection which has a unique connection identifier (CID). The packets between BS and AR are carried using L2 tunnel (typically GRE tunnel) so that MS and AR are seen as layer 3 peer entities. At least one L2 tunnel is required for each MS, so that IP packets can be sent to MSs before they acquire IP addresses. The figure below Madanapalli & Park Expires August 11, 2007 [Page 3] Internet-Draft IPv4 over 802.16's IP CS February 2007 illustrates the network architectures. +-----+ CID1 +------+ +-----------+ | MS1 |----------+| BS |----------| AR |-----[Internet] +-----+ / +------+ +-----------+ . / ____________ . CIDn / ()__________() +-----+ / L2 Tunnel | MSn |-----/ +-----+ Figure 1: Typical Network Architecture for IPv4 over 802.16 The above network model serves as an example and is shown to illustrate the point to point link between the MS and the AR. The L2 tunnel is not required if BS and AR are integrated into a single box. 4. Frame Format for IPv4 Packets IPv6 packets are transmitted in Generic 802.16 MAC frames as shown in the following figure. Madanapalli & Park Expires August 11, 2007 [Page 4] Internet-Draft IPv4 over 802.16's IP CS February 2007 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |H|E| TYPE |R|C|EKS|R|LEN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LEN LSB | CID MSB | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CID LSB | HCS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 | +- -+ | header | +- -+ | and | +- -+ / payload ... / +- -+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |CRC (optional) | +-+-+-+-+-+-+-+-+ Figure 2: 802.16 MAC Frame Format for IPv4 Packets H: Header Type (1 bit). Shall be set to zero indicating that it is a Generic MAC PDU. E: Encryption Control. 0 = Payload is not encrypted; 1 = Payload is encrypted. R: Reserved. Shall be set to zero. C: CRC Indicator. 1 = CRC is included, 0 = 1 No CRC is included EKS: Encryption Key Sequence LEN: The Length in bytes of the MAC PDU including the MAC header and the CRC if present (11 bits) CID: Connection Identifier (16 bits) HCS: Header Check Sequence (8 bits) CRC: An optional 8-bit field. CRC appended to the PDU after encryption. TYPE: This field indicates the subheaders (Mesh subheader, Fragmentation Subheader, Packing subheader etc and special payload types (ARQ) present in the message payload 5. Maximum Transmission Unit The Length parameter of 802.16 MAC frame has a size of 11 bits. Hence the total PDU size is 2048 bytes. The IPv4 payload can be a maximum value of 2038 bytes ( Total PDU size (2048) - (MAC Header (6) Madanapalli & Park Expires August 11, 2007 [Page 5] Internet-Draft IPv4 over 802.16's IP CS February 2007 + CRC (4)). The default MTU for IPv4 over 802.16 SHOULD be 1920, this would accommodate tunneling overhead for delivering the packets between BS and AR. This size may be reduced or increased by a Path MTU Discovery [8] or by manual configuration of each MS. The minimum and maximum MTUs for IPv4 packets over 802.16 with IPv4 CS are 576 bytes and 2038 bytes respectively. 6. IPv4 Address Assignment DHCP [4] SHOULD be used for assigning IPv4 address for the MSs. DHCP messages are transported over 802.16 MAC transported connection to and from the AR. In case DHCP server does not reside in AR, the AR SHOULD implement DHCP relay Agent [5]. The DHCP Relay Agent MUST store the information on which interface (L2 Tunnel) it has received the DHCP messages, so that it can relay the DHCP responses to the correct MS. 7. Address Resolution Protocol The 802.16 frame header does not contain the source and destination MAC addresses, instead it uses the Connection Identifier (CID) for the MAC frames delivery. This makes classical Address Resolution Protocol (ARP) [3] trivial and unnecessary. If an MS initiates an ARP for address resolution, the AR SHOULD silently discard the ARP packet. All the outgoing packets that arrive at IPv4 layer, should be given to 802.16's IPv4 CS, which would map the packets to appropriate MAC transport connection. The AR MUST be configured as the default gateway for the MSs that have been attached to it. ICMP Router Discovery [9] may be used for discovering the AR IP address. 8. IP Multicast Address Mapping Mapping of multicast IP address to a MAC address is not required as the 802.16 MAC address is not used for delivering the MAC frames. The 802.16 uses the Connection ID (CID) for frame delivery hence no address mapping is required. 9. Sending and Receiving IPv4 Packets 802.16 MAC is a point-to-multipoint connection oriented air- interface, and the process of sending and receiving of IPv4 packets is different from multicast capable shared medium technologies like Madanapalli & Park Expires August 11, 2007 [Page 6] Internet-Draft IPv4 over 802.16's IP CS February 2007 Ethernet. Before any packets being transmitted, 802.16 transport connection must be established. This connection is consists of 802.16 MAC transport connection between MS and BS and an L2 tunnel between BS and AR. This 802.16 transport connection provides a point-to-point link between MS and AR. all the packets originated at the MS always reach AR before being transmitted to the final destination. IPv4 packets are carried directly in the payload of 802.16 frames when the IPv4 CS is used. IPv4 CS classifies the packet based on upper layer (IP and transport layers)header fields to put the packet on one of the available connections identified by the CID. The classifiers for the IPv4 CS are source and destination IPv4 addresses, source and destinations ports, Type-of-Service and IP protocol field. The CS may employ Packet Header Suppression (PHS) after the classification. The BS tunnels the packet that has been received on a particular MAC connection to the AR. BS reconstructs the payload header if the PHS is in use before being the packet is tunneled to the AR. Similarly the packets received on a tunnel interface from the AR, would be mapped to a particular CID using IPv4 classification mechanism. AR performs normal routing for the packets that it receives and forwards the packet based on its forwarding table. However the DHCP relay agent in the AR, MUST maintain the tunnel interface on which it receives DHCP requests, so that it can relay the DHCP responses to the correct MS. One way of doing this is to have a mapping between MAC address and Tunnel Identifier. 10. Security Considerations This document specifies transmission of IPv4 packets over 802.16 networks with IPv4 Convergence Sublayer and does not introduce any new vulnerabilities to IPv4 specifications or operation. The security of the 802.16 air interface is the subject of [6]. 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 [7]. 11. IANA Considerations This document has no actions for IANA. Madanapalli & Park Expires August 11, 2007 [Page 7] Internet-Draft IPv4 over 802.16's IP CS February 2007 12. Acknowledgements TBD. 13. References 13.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [3] Plummer, D., "Ethernet Address Resolution Protocol: Or converting network protocol addresses to 48.bit Ethernet address for transmission on Ethernet hardware", STD 37, RFC 826, November 1982. [4] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [5] Wimer, W., "Clarifications and Extensions for the Bootstrap Protocol", RFC 1542, October 1993. 13.2. Informative References [6] "IEEE 802.16e, IEEE standard for Local and metropolitan area networks, Part 16:Air Interface for fixed and Mobile broadband wireless access systems", October 2005. [7] "WiMAX End-to-End Network Systems Architecture, http://www.wimaxforum.org/technology/documents", August 2006. [8] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, November 1990. [9] Deering, S., "ICMP Router Discovery Messages", RFC 1256, September 1991. [10] Jee, J., "IP over 802.16 Problem Statement and Goals", October 2006, . Madanapalli & Park Expires August 11, 2007 [Page 8] Internet-Draft IPv4 over 802.16's IP CS February 2007 Authors' Addresses Syam Madanapalli LogicaCMG Bangalore India Email: smadanapalli@gmail.com Soohong Daniel Park Samsung Electronics 416 Maetan-3dong, Yeongtong-gu Suwon 442-742 Korea Email: soohong.park@samsung.com Madanapalli & Park Expires August 11, 2007 [Page 9] Internet-Draft IPv4 over 802.16's IP CS February 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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, THE IETF TRUST 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. Intellectual Property 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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Madanapalli & Park Expires August 11, 2007 [Page 10]