Internet DRAFT - draft-neumiller-req
draft-neumiller-req
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
<draft-neumiller-req-00.txt>
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
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The list of current Internet-Drafts can be accessed at
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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.
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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
<youremail>" 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
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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
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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.
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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.
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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.
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