INTERNET DRAFT Phillip D. Neumiller Peter Lei Randall Stewart Qiaobing Xie Motorola, Inc. Patrice Calhoun Jack Kempf Sun Microsystems, Inc. 15 June 2000 John Loghney Nokia, Inc. Open Base Station Transport (OBAST) Requirements Status of This Memo ------------------- This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents, valid for a maximum of six months, and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract -------- This document outlines the requirements for a set of open IP based protocols enabling seamless mobility across diverse radio access networks. This document begins by stating some architectural tenets upon which the requirements for the OBAST protocol set are based. Neumiller, et al, Page 1 of 1 INTERNET-DRAFT Open Base Station Transport Requirements June 2000 Furthermore, what the authors currently believe to be the eventual desirable wireless Internet architecture is described. This architecture is shown to enable a common protocol set that we refer to as open base station transport (OBAST). Contents Status of This Memo 1 Abstract 1 1. Introduction 2 1.1 Terminology 2 2. Review of Architectural Tenets 3 3. Baseline OBAST Implied Architecture 6 1. Introduction ====================== This document lists requirements for a protocol set enabling access points and/or base stations, of different radio access network types, to communicate with each such that seamless handovers may occur between these radio nodes. We refer to this protocol set as: Open Base Station Transport (OBAST). A mailing list has been set up for OBAST at majordomo@cig.mot.com; simply put "subscribe obast-list " in the body of a message sent to this address. There are fundamental architectural tenets that facilitate "seamless roaming". We shall review those first by speaking in terms of what OBAST is and isn't. 1.1 Terminology --------------------- AP = access point BTS = base transceiver station CDG-IOS = CDMA Development Group-Inter-Operability Standard CDMA = Code Division Multiple Access GSM = Global System for Mobile communications OBAST = Open Base Station Transport Macro-mobility = Inter-IP domain mobility MAP = Mobile Application Part Micro-mobility = intra-IP domain mobility PSTN = Public Switched Telephone Network RAN = Radio Access Network RNC = Radio Network Controller Neumiller, et al., Expires December 2000 Page 2 of 2 INTERNET-DRAFT Open Base Station Transport Requirements June 2000 SDU = Selection Distribution Unit SS7 = Signaling System 7 TIA = Telecommunications Industry Associates UMTS = Universal Mobile Telephone System WLAN = Wireless Local Area Network WPAN = Wireless Personal Area Network 2. Review of Architectural Tenets ======================================== Simplicity ---------- There is a huge amount of commonality between the SS7 ISUP/IS-41 and GSM MAP signaling sets used for inter-system mobility in classical cellular deployments. There is also a large amount of functional overlap at the TIA reference points above A-bis (the point of base station attachment to the rest of the network), where IuPs, GSM A- bis, and CDG-IOS (IS-634) all play a role on UMTS, GSM systems, and CDMA systems respectively. There are several micro-mobility proposals including Cellular IP, hierarchical Mobile IP, EMA, HAWAII, and IAPP (now an IEEEE standard) for 802.11 access. The inter- network protocols between deployed cellular systems will likely remain in place for a long time. However, by pushing all radio related behavior down into the BTS or AP, OBAST hopes to simplify the "top of the access point protocol" and eventually provide seamless roaming between wireless personal area networks (WPANs), wireless LANs (WLANs), and next generation cellular networks. OBAST is Open and Universal --------------------------- The current situation in radio access networks is that they are closed and require complicated protocols to inter-network, if internetworking is possible at all. OBAST seeks to open up radio access networks to provide the same kind of internetworking that has been so successful in the wired world. The history of the Internet has proven that open protocols have a distinct technological advantage, because they are developed, reviewed, and implemented, by a broad group of network experts. A distinct economic advantage can be gained from openness, because open protocols tend to encourage competition around the quality of the implementation rather than around comparisons of feature sets that may or may not be of benefit to users. We believe these properties will hold for the wireless Internet as well. Historically, RANs have been tightly coupled to the core cellular network so that cellular equipment could not be easily replaced without extensive modification to the core network as well. The existing 3G standards are propagating this architectural tendency Neumiller, et al., Expires December 2000 Page 3 of 3 INTERNET-DRAFT Open Base Station Transport Requirements June 2000 forward, but in a world where wireless options are multiplying, such closed non-inter-networking solutions become less and less viable. The OBAST architecture attempts to push "all" radio control and knowledge to the base stations so that a common and universal inter- access point or inter-BTS mobility protocol can be created. We believe that this protocol is only useful if it gains critical mass on the global Internet. We feel it can evolve with the global Internet in such a way as to someday abolish the need for core networks and radio specific standards. OBAST is Forward Looking ------------------------ The momentum behind existing 3G standards may discourage deployment of any OBAST protocols in existing cellular networks. However, we believe greenfield 3G markets and WPAN deployments and WLAN investments could potentially benefit immediately from its adoption. It is our ambition to make OBAST a protocol set supporting the most advanced, scalable, and forward looking wireless Internet architecture. OBAST is a Protocol Set, However, It Implies Architectural Change ----------------------------------------------------------------- For OBAST to meet its goals, it requires a change in the way wireless networks have been classically designed. The primary architectural changes are (1) the BTS or AP becomes the one and only building block of the radio access network, (2) All radio control terminates at the BTS or AP and nothing radio specific creeps out above the BTS or AP. OBAST Promotes Seamless Mobility -------------------------------- Having a common protocol for micro-mobility and macro-mobility, AAA, and QoS, independent of access network type is OBAST's primary end goal. Facilitating the fixed to wireless network transition is also part of the ultimate end goal, but not a primary focus. OBAST will focus first on a protocol set, borrowed from other standards as much as possible and invent only where white spaces exist. OBAST Promotes Peer-to-Peer Protocols ------------------------------------- Peer-to-peer protocols imply that no master or slave is assumed. OBAST will support the concept of elected call anchors that follow the mobiles as they move through "a sea of BTSs or access points". The call anchor has the responsibility of terminating the radio portion of the call. The call anchor is also responsible for orchestrating handover requests for the mobile. The call anchor is the point of selection and distribution when macro-diversity is required. Neumiller, et al., Expires December 2000 Page 4 of 4 INTERNET-DRAFT Open Base Station Transport Requirements June 2000 OBAST Promotes IPv6 and MIPv6 Everywhere ---------------------------------------- OBAST could be made to run over IPv4. However, being a new protocol we wish to architect it to run over IPv6 primarily and this is what we will focus on. We will also promote the use of MIPv6 clients everywhere to enable enhanced macro-mobility. OBAST Will not Re-invent or Invent AAA or QoS Mechanisms -------------------------------------------------------- Every attempt to will be made to be agnostic to these protocols where possible. OBAST may eventually need to endorse or provide minimal AAA and QoS mechanism negotiation to facilitate seamless handovers. Much work is being done in this area, so OBAST will defer incorporating AAA or QoS mechanisms into its protocol set until after the seamless mobility issues have been resolved. OBAST Recognizes Other Important Standards ------------------------------------------ The pilc, mobileip, cnrp, slp, zeroconf, aaa, manet, diffserv, intserv, rsvp, pint, sip, rohc, IETF working groups all contain work useful to making OBAST happen. OBAST does/ will not replace/ dilute/ change efforts under way in 3GPP, 3GPP2, MWIF, or 3G.IP. OBAST shall be Air Interface Agnostic ------------------------------------- OBAST will enable seamless roaming between WLANs (eg 802.11), WPANs (eg Bluetooth), and macro-cellular (eg EDGE, 3G-1X, etc). As such, OBAST must not favor any particular radio type over another. OBAST recognizes that there are going to be LOTS of competing radio technologies making their debut over the next few years and many portable devices will support multiple RF interfaces. OBAST Shall Work Diligently on Micro-mobility --------------------------------------------- OBAST supports the ideas behind IAPP (but not necessarily the implementation). OBAST is looking critically at CellularIP, HAWAII, EMA, and the work going on in the mobileip working group that will be speeding up mobileip hand-overs. OBAST will be flexible enough to support multiple negotiable micro-mobility schemes but may have to choose one as a minimum required protocol set to support "seamlessness". OBAST Shall Attempt To Remain Agnostic to Call Processing --------------------------------------------------------- Session initiation methods like SIP must be somewhat transparent to OBAST. It is not clear how this can be best done and this is considered a challenge. Neumiller, et al., Expires December 2000 Page 5 of 5 INTERNET-DRAFT Open Base Station Transport Requirements June 2000 OBAST Shall Make the Most out of SCTP ------------------------------------- OBAST will support the use of SCTP (sigtran) for inter-radio node signaling and possibly for transport applications (yet to be determined). 3. Baseline OBAST Implied Architecture --------------------------------------------- Using OBAST implies a new (at least to cellular and WLAN standards) view of the "Wireless Internet architecture". This architecture has two component types: routers (that make up the global Internet), and base stations / access points. In this view, the edge routers themselves could possibly have radio cards and be OBAST compliant. We feel that the scalability for routers has been proven on the global Internet. Radios, as edge devices, must respect this fundamental nature of the Internet architecture. The figure below shows the relationship between these simple components. (Global Internet) | . . . | OBAST OBAST | | AP BTS <- OBAST enabled Radio Access Nodes The radio coverage, for the OBAST BTS (shown above), may engulf that of the AP, implying a vertical handover being required in this scenario. OBAST must facilitate vertical, horizontal, soft and hard handovers at the radio and at the servicing network layer when required or optimal. Neumiller, et al., Expires December 2000 Page 6 of 6