RFC2636 - Wireless Device Configuration (OTASP/OTAPA) via ACAP

Network Working Group R. Gellens
Request for Comments: 2636 Qualcomm
Obsoletes: 2604 July 1999
Category: Informational
Wireless Device Configuration (OTASP/OTAPA) via ACAP
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
Wireless carriers today are faced with creating more efficient
distribution channels, increasing customer satisfaction, while also
improving margin and profitability. Industry trends are pushing the
sale of handsets further into the retail channel. The cost and
effort of provisioning handsets, activating users, and updating
handset parameters can be greatly redUCed by using over-the-air
activation mechanisms. A comprehensive and extensible means for
over-the-air provisioning and handset parameter updating is required.
One approach is to purchase EIA/TIA/IS-683A (Over-the-air Service
Provisioning of Mobile Stations in Spread Spectrum Systems)
equipment. The cost of this has led carriers to seek alternative
solutions. A very viable means for providing over-the-air (OTA)
provisioning is to leverage the rollout of IS-707 data services
equipment, which most carriers are in the process of deploying. This
paper presents an approach to OTA provisioning that utilizes the
deployment of IS-707 to deliver OTA provisioning and parameter
upgrading.
IS-707 data services makes available several methods of providing
over-the-air provisioning and parameter updating. A well thought-out
approach utilizing Internet-based open standard mechanisms can
provide an extensible platform for further carrier service offerings,
enhanced interoperability among back-end services, and vendor
independence.
This paper describes a viable and attractive means to provide
OTASP/OTAPA via IS-707, using the ACAP [ACAP] protocol.
Table of Contents
1. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Feature Descriptions . . . . . . . . . . . . . . . . . . . 6
2.1. OTASP Feature Description . . . . . . . . . . . . . . . 6
2.2. OTAPA Feature Description . . . . . . . . . . . . . . . 6
3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Initial Provisioning Activity . . . . . . . . . . . . . 7
3.2. OTASP for Authorized Users . . . . . . . . . . . . . . . 8
3.3. OTAPA Activity . . . . . . . . . . . . . . . . . . . . 8
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. General Requirements . . . . . . . . . . . . . . . . . 9
4.2. OTASP Requirements . . . . . . . . . . . . . . . . . . . 9
4.3. OTAPA Requirements . . . . . . . . . . . . . . . . . . 10
4.4. Provisioning Server Requirements . . . . . . . . . . . . 10
4.5. Security Requirements . . . . . . . . . . . . . . . . . 11
5. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. ACAP over TCP/IP . . . . . . . . . . . . . . . . . . . 11
5.1.1. Mobile Authentication and A-Key Generation . . . . . 12
5.1.2. Mobile Identification . . . . . . . . . . . . . . . 12
5.1.3. ACAP Server . . . . . . . . . . . . . . . . . . . . 12
5.1.4. Overview of ACAP Structure . . . . . . . . . . . . 13
5.1.5. Data Organization and Capabilities . . . . . . . . . 13
5.1.5.1. Structure . . . . . . . . . . . . . . . . . . . 14
5.1.5.2. Conventions . . . . . . . . . . . . . . . . . . 15
5.1.5.3. Dataset . . . . . . . . . . . . . . . . . . . . 15
5.1.5.4. Entries and Attributes . . . . . . . . . . . . . 15
5.1.5.5. NAM Records . . . . . . . . . . . . . . . . . . 16
5.1.5.6. Server Roaming Lists . . . . . . . . . . . . . . 17
5.1.5.7. Requested-Data Record . . . . . . . . . . . . . 18
5.1.5.8. Sample Server Entry . . . . . . . . . . . . . . 18
5.1.6. Administrative Client . . . . . . . . . . . . . . . 19
5.1.7. Mobile Client . . . . . . . . . . . . . . . . . . . 20
5.2. WAP with ACAP . . . . . . . . . . . . . . . . . . . . . 22
5.3. Network-Resident vs. Configuration Data . . . . . . . . 23
5.4. Intellectual Property Issues . . . . . . . . . . . . . 23
6. Handset Protocol Suites . . . . . . . . . . . . . . . . . . 23
6.1. ACAP over TCP/IP . . . . . . . . . . . . . . . . . . . 23
7. IS-683A Compatibility . . . . . . . . . . . . . . . . . . . 24
7.1. OTASP Operations . . . . . . . . . . . . . . . . . . . 24
7.2. OTASP Call Flow . . . . . . . . . . . . . . . . . . . . 24
7.3. OTAPA Operations . . . . . . . . . . . . . . . . . . . 24
7.4. OTAPA Call Flow . . . . . . . . . . . . . . . . . . . . 25
8. Alternative Methods . . . . . . . . . . . . . . . . . . . . 25
8.1. IS-683A over TCP/IP . . . . . . . . . . . . . . . . . . 25
8.1.1. OTAF Server . . . . . . . . . . . . . . . . . . . . 25
8.1.2. Interface Application . . . . . . . . . . . . . . . 26
8.1.3. Protocol Handset Suite . . . . . . . . . . . . . . 26
8.2. Browser-Based Forms . . . . . . . . . . . . . . . . . . 26
9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . 28
11. Security Considerations . . . . . . . . . . . . . . . . . 28
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 28
13. Author"s Address . . . . . . . . . . . . . . . . . . . . 28
14. Full Copyright Statement . . . . . . . . . . . . . . . . . 29
1. Terms
Application Configuration Access Protocol (ACAP) -- An Internet
protocol (RFC-2244) that provides remote storage and access of
configuration and preference information.
Activation -- A process in which a mobile station and network become
programmed so that a mobile station becomes operable and can be used
for cellular service once authorized by the service provider.
Authentication -- A procedure used to validate a mobile station"s
identity.
Authentication Center -- An entity that manages the authentication
information related to the mobile station.
Authentication Key (A-key) -- A secret 64-bit pattern stored in the
mobile station. It is used to generate and update the mobile
station"s shared secret data. The A-key is used in the
authentication process.
Authorization -- An action by a service provider to make cellular
service available to a subscriber.
Call -- A temporary communication between telecommunications users
for the purpose of exchanging information. A call includes the
sequence of events that allocates and assigns resources and signaling
channels required to establish a communications connection.
Cellular Service Provider -- A licensee of the responsible government
agency (in the U.S. a licensee of the Federal Communications
Commission) authorized to provide Cellular Radiotelephone Service.
Challenge/Response Authentication Mechanism using Message Digest 5
(CRAM-MD5) -- An authentication mechanism which is easy to implement,
and provides reasonable security against various attacks, including
replay. Supported in a variety of Internet protocols. Specified as
baseline mechanism in ACAP. CRAM-MD5 is published as RFC2195.
Code Division Multiple Access -- A technique for spread-spectrum
multiple-access digital communications that creates channels through
the use of unique code sequences.
Customer Service Center -- An entity of a service provider that
provides user support and assistance to subscribers.
Customer Service Representative -- A person that operates from a
customer service center and provides user support and assistance to
subscribers.
Diffie-Hellman Algorithm -- A public-key cryptography algorithm for
exchanging secret keys. Uses the equation , where k is the secret
key. The equation is executed by each party of the session based on
the exchange of independently generated public values.
Digits -- Digits consist of the decimal integers 0,1,2,3,4,5,6,7,8,
and 9.
Dual-mode Mobile Station -- A mobile station capable of both analog
and digital operation.
Electronic Serial Number (ESN) -- A 32-bit number assigned by the
mobile station manufacturer used to identify a mobile station. The
ESN is unique for each legitimate mobile station.
Home Location Registry (HLR) -- The location register or database to
which a MIN is assigned for record purposes such as subscriber
information.
Message Digest 5 (MD5) -- A one-way cryptographic hash function.
Widely deployed in Internet protocols. Published as RFC1321.
Mobile Identification Number (MIN) -- The 10-digit number that
represents a mobile station"s Directory number.
Mobile Station (MS) -- A station, fixed or mobile, which serves as
the end user"s wireless communications link with the base station.
Mobile stations include portable units (e.g., hand-held personal
units) and units installed in vehicles.
Mobile Switching Center (MSC) -- A configuration of equipment that
provides cellular radiotelephone service.
Mobile Terminal Authorizing System (MTAS) -- A control system that
provides the capability to load the CDMA network HLR with mobile
station profile information.
Number Assignment Module (NAM) -- The mobile station"s electronic
memory module where the MIN and other subscriber-specific parameters
are stored. Mobile stations that have multi-NAM features offer users
the option of using their units in several different markets by
registering with a local number in each location.
Over-the-air Service Provisioning Function (OTAF) -- A configuration
of network equipment that controls OTASP functionality and messaging
protocol.
Over-the-air Parameter Administration (OTAPA) -- Network initiated
OTASP process of provisioning mobile station operational parameters
over the air interface.
Over-the-air Service Provisioning (OTASP) -- A process of
provisioning mobile station operational parameters over the air
interface.
Quick-Net-Connect (QNC) -- An IS-707 data service capability that
utilizes the Async Data Service Option number but bypasses the modem
connection for a direct connection to an IP-based internet.
Roamer -- A mobile station operating in a cellular system or network
other than the one from which service was subscribed.
Simple Authentication and Security Layer (SASL) -- An Internet
protocol (RFC-2222) that provides a framework for negotiating
authentication and encryption mechanisms.
Service Provider -- A company, organization, business, etc. which
sells, administers, maintains, and charges for the service. The
service provider may or may not be the provider of the network.
Shared Secret Data (SSD) -- A 128-bit pattern stored in the mobile
station (in semi-permanent memory) and known by the network. The A-
key is used to generate the SSD at the network and in the mobile
station for comparison.
Wireless Application Protocol (WAP) -- A set of network and
application protocols including a datagram protocol (WDP), Transport
Layer Security (WTLS), Transaction Protocol (WTP), Session Protocol
(WSP), and Application Environment (WAE), which use carrier-based
gateways to enable wireless devices to access Web resources. See
<http://www.wapforum.org> for specifications and details.
2. Feature Descriptions
2.1. OTASP Feature Description
The Over the Air Service Provisioning (OTASP) feature allows a
potential wireless service subscriber to activate new wireless
services, and allows an existing wireless subscriber to make
services changes without the intervention of a third party. OTASP
includes the following:
* A way to establish a user profile.
* "Over-The-Air" programming of a Number Assignment Module (NAM),
IMSI and Roaming Lists, including Data option parameters, and
optionally, service provider or manufacturer specific parameters
(e.g., lock code, call timer).
* An Authentication Key (A-key) Generation procedure.
* A-key storage
2.2. OTAPA Feature Description
The Over-the-Air Parameter Administration (OTAPA) feature allows
wireless service providers to update a NAM, IMSI, and Roaming List
information in the mobile station remotely without the intervention
of a third party. This capability increases flexibility and reduces
costs for carriers involved with mass changes that affect every
handset, such as area-code splits.
OTAPA includes the following:
* Update a user"s Number Assignment Module (NAM)
* Update Data option parameters
* Update service provider or manufacturer specific parameters (e.g.,
Server address(es), lock code, call timer).
* Update roaming lists
3. Operation
3.1. Initial Provisioning Activity
A new subscriber needs to give the intended service provider
sufficient information (e.g., name, address, etc.) to prove credit-
worthiness and establish a record within the service provider"s
billing system. In addition, the ESN of the mobile station needs to
be given to the provider. This may occur in three ways:
Voice scenario -- A customer care representative collects credit
information during a voice conversation. This call is made from a
different phone (e.g., wired service) or is initiated using the IS-
683A OTASP dialing scheme (i.e., *228xx).
Once the user has been authorized, the customer care representative
creates a record in the CDMA network HLR, thus allowing use of the
CDMA network. In addition, a limited-time N-digit passWord is
created which is tied to the ESN. The choice of N (how many digits)
is up to the carrier (as a trade-off between security and user
inconvenience). All required provisioning information (including
the limited-time password) is loaded into the provisioning server.
The user is then told to hang up and call a special number, of the
form *228 XX <N-digit password> SEND (the XX code is the same as
used in the initial voice call). This causes the mobile station to
initiate a provisioning session.
The mobile station and the provisioning server authenticate, and all
required provisioning information is downloaded into the mobile
station. The user receives some form of notification once the
activity is complete. This notification can be an audible tone or a
text message on the mobile station display. (The form and content of
this notification can be part of the provisioning data downloaded by
the mobile station.) Once this initial provisioning activity is
complete the user has a fully authorized mobile station ready for
use.
Forms scenario -- An interactive user interface is presented via a
browser on the mobile station. The subscriber fills in the
requested information. (Note that entering non-numeric data presents
some user interface challenges on many mobile devices.)
A back-end server validates the information, and if possible, the
customer is authorized, a limited-time password is generated, HLR
and provisioning server records are created and the actual OTASP
operation begins. Otherwise, a voice call is made to a customer
care representative.
Desktop scenario -- The subscriber uses a desktop (or in-store
kiosk) web browser to contact the carrier, and enters the usual
personal information.
The carrier"s server validates the information, and if possible, the
customer is authorized, a limited-time password is generated, HLR
and provisioning server records are created, and the subscriber is
told to dial a special number on the handset. Once this code is
entered, the actual OTASP operation begins. Otherwise, the user is
asked to make a voice call to a customer care representative.
3.2. OTASP for Authorized Users
Users already authorized for use of the CDMA network can also
initiate provisioning activity. This could happen after being
directed to do so by a Customer Care representative, either from a
phone conversation or via mail notification. This type of OTASP
activity is needed in cases where the carrier desires to upgrade
CDMA parameters in the mobile stations or in cases where mobile
station troubleshooting is needed.
This type of OTASP occurs in similar fashion to the initial OTASP
activity. The mobile station downloads the new provisioning
information in the same way.
3.3 OTAPA Activity
Typical OTAPA capability involves upgrading a large number of mobile
stations. OTAPA activity needs to be performed in a manner that
does not impose on revenue bearing CDMA network activity. OTAPA
operations are initiated at the customer care center. This can be
accomplished by queuing a notification to the mobile station (via
1-way SMS or special caller-ID) after the provisioning server has
the updated configuration data. OTAPA activity will not occur until
the mobile station has acquired CDMA service on the carrier"s
network and the notification has reached the mobile station.
Alternatively, OTAPA can be handled by including a recheck interval
in the set of data used to provision the mobile station. When using
a low-overhead protocol, such as ACAP [ACAP], it is reasonable to
have a mobile station check in periodically to see if anything has
changed. The time of day and/or day of week that such rechecks
should occur could be included in the provisioning data.
OTAPA activity can be terminated at any time due to user call
activity.
4. Requirements
4.1. General Requirements
IS-683A OTASP operations occur between a mobile station and an
over-the-air service provisioning function (OTAF) using IS-95A
traffic channel data burst messages. OTASP/OTAPA via data services
require that the CDMA carrier have an IS-707 data services capable
network. The IS-707 service must be either Packet Data Service
(IS-707.5) or Quick-Net-Connect (QNC).
The mobile station must support:
* IS-707 Data Service capability
* Packet/QNC RLP protocol
* PPP protocol to peer to the IS-707 IWF
* IP protocol to provide the network layer for routing to the
provisioning server
* A transport layer for end-to-end communication (such as TCP)
* Authentication and optionally encryption
* Application software to handle the provisioning protocol and
memory access.
* Domain Name System (DNS) query capabilities sufficient to oBTain
the (IP) address of the provisioning server (or the provisioning
server"s address could be provided during PPP negotiation).
Lastly, the ability must exist for the mobile to make a data call
(optionally) a voice call without a MIN.
4.2. OTASP Requirements
The OTASP function requires the mobile station to originate an IS-
707 data call and (optionally) a voice call using a completely
unprovisioned mobile station. The CDMA network must support this
capability.
OTASP via data services uses a provisioning server that contains the
parameter information for mobile stations. The authorizing agent
(or software) at the customer care center must be able to add user
and mobile station information into both the CDMA network HLR and
the provisioning server during the initial authorizing process. The
provisioning server must be capable of servicing a mobile as soon as
its record is created.
4.3. OTAPA Requirements
IS-683A OTAPA is performed by a mobile-terminated call that
downloads parameters to the mobile station. OTAPA calls occur
without user interaction.
In order to perform OTAPA via data services the network needs to
direct the mobile station to initiate a special-purpose data call.
Several existing methods can be used to implement this capability,
for example, a mobile-terminated one-way SMS message. The SMS
message content can contain any information required by the mobile
station. The mobile station would need a simple parser of SMS
messages in order to know when to originate an OTAPA call, as
opposed to normal SMS message processing. The OTAPA call would be
performed in similar fashion to a registration call. More
specifically, the user would not be informed of the call activity.
There are alternative means that can be employed to initiate OTAPA
activity; for example, a mobile-terminated voice call with caller-ID
using a specialized telephone number. Another alternative is for
mobile stations to periodically check in with the provisioning
server to check for updated information. ACAP, for example, is
designed for such a model. The recheck interval, as well as the
time of day and/or day of week that such checks should be used, can
be part of the provisioning data sent to the mobile stations.
4.4. Provisioning Server Requirements
IS-683A utilizes an over-the-air service provisioning function
(OTAF) to perform the network-side provisioning activity.
OTASP/OTAPA via data services replaces the OTAF with a provisioning
server. The provisioning server resides on an IP network within the
controlled confines of the carrier. The provisioning server must
perform all the service provisioning and parameter administration
functions that the OTAF provides. The provisioning server must also
have an interface to the carrier"s Mobile Terminal Authorizing
System (MTAS). This interface serves to synchronize the
provisioning server with the information in the MTAS. The specific
requirements of this interface depend on the capabilities and
interfaces of the carrier"s customer care center system(s). The
provisioning server must be capable of receiving dynamic updates
from the MTAS and have the provisioning information immediately
available for downloading into the chosen mobile station. A
standard ACAP server provides an Excellent means to meet these
requirements.
The provisioning server must be capable of performing an
authentication procedure with the mobile station. This
authentication mechanism must be capable of authenticating both the
mobile station and the provisioning server.
4.5. Security Requirements
OTASP requires that an authentication procedure be performed to
validate the mobile station to the provisioning server, while OTAPA
requires a mechanism where the mobile validates the server.
The provisioning server must be capable of either:
* OTAF A-key generation using a Diffie-Hellman mechanism
Or:
* Receiving A-keys from the carrier network.
Since data OTASP/OTAPA operates over IP within the carrier"s
network, end-to-end encryption between the mobile station and the
provisioning server should be considered as a future enhancement.
End-to-end encryption protects against attacks from within a
carrier"s network, and safeguards the provisioning data (for
example, roaming lists).
5. Architecture
5.1. ACAP over TCP/IP
Figure 1 shows a provisioning server in the carrier"s intranet which
supports the Application Configuration Access Protocol (ACAP, RFC
2244). An administrative client in the customer care domain updates
this server using ACAP. Handsets are provisioned and configured
using a small ACAP client.
[Figure 1 -- see PostScript version]
ACAP is an open Internet protocol designed to solve the problem of
client access to configuration and related data. Among its primary
goals are protocol simplicity, support for thin clients, and ease of
operation over limited bandwidth. ACAP provides a high degree of
extensibility, especially in authentication mechanisms, specialized
attribute handling, and data management.
5.1.1. Mobile Authentication and A-Key Generation
The mobile client authenticates with the ACAP server prior to
performing any activities. Authentication uses the mobile"s ESN and
a shared secret. Provisioned mobiles derive the shared secret from
the A-Key; unprovisioned mobiles use a limited-time password as the
secret.
The limited-time password is provided to the user by the Customer
Care representative during the initial call (as instructions to dial
a specific number). This code is N digits long. The carrier
selects the number of digits, as a trade-off between security and
user convenience.
The baseline ACAP authentication mechanism uses the shared secret
plus a random challenge from the server as input to a one-way
cryptographic hash function (specifically, keyed-MD5). This is
analogous to the existing IS-683A authentication mechanism which
uses a random challenge and the CAVE algorithm.
An A-Key is generated using a Diffie-Hellman exchange, as is done in
IS-683A.
5.1.2. Mobile Identification
Provisioning records are identified using the ESN and the current
NAM in use.
5.1.3. ACAP Server
As a standard ACAP server, the provisioning server includes
configurable datasets and dataset inheritance for the management of
the data stores.
The administrative client can use the same simple ACAP protocol to
load and modify the ACAP server as the mobile stations uses for
provisioning. While any implementation-specific mechanisms
available from the server vendor could instead be used for this
purpose, the ability to use ACAP can greatly simplify the
administrative client, as well as make it independent of the server.
ACAP includes an authentication framework (Simple Authentication and
Security Layer, SASL, RFC2222)[SASL]. SASL allows any standard or
custom authentication and encryption mechanism to be used. One of
the most important features of SASL is that it is designed for a
world in which what is "good enough" security today isn"t good
enough tomorrow. As the threat model changes, SASL allows higher-
strength mechanisms to be easily added while supporting already
deployed clients and servers. SASL is achieving widespread
deployment in a number of Internet protocols.
Strongpoints: Since the ACAP protocol was designed for precisely
this type of provisioning activity, its adoption can greatly reduce
the cost, time to market, and support required for the provisioning
server. Additionally, the ACAP protocol provides an open standard
method for mobile stations and other systems to access the
provisioning server. Commercial ACAP servers are being developed by
numerous companies. The ACAP client code is very small and simple,
and thus can be incorporated into virtually any mobile device at
minimal cost. As an open standard, the ACAP protocol has benefited
from years of review and eXPerience.
5.1.4. Overview of ACAP Structure
ACAP organizes data by datasets. The structure of a dataset is
defined by the dataset class. Generally, ACAP servers do not have
knowledge of dataset classes. This allows the dataset to be
expanded without modifying the server in any way. A dataset is an
instantiation of the dataset class, which is a logical definition of
what is in a dataset, and how it is used.
Datasets contain entries. Entries contain attributes and values.
Attributes and values are actually metadata, such as name, length,
and value. Any entry can also be a dataset (datasets are
hierarchical).
For example, consider the ACAP addressbook dataset class, designed
to hold names, email addresses, phone numbers, and related
information for a person"s contacts. A given user may have one or
more addressbook datasets. Each entry holds information about one
person or entity. Attributes in the entry hold specific items of
information, such as the given name, surname, various email
addresses, phone numbers, and so forth. If an entry is a list of
people (such as a mailing list or specific group of people), it is a
subdataset, containing its own entries. Some clients may look at
only a subset of the attributes. For example, a mobile handset ACAP
client may download only the alias (nickname), name, primary phone
number and email address of each entry, while a desktop client may
access all attributes.
5.1.5. Data Organization and Capabilities
ACAP provides custom hierarchical datasets. Server data can be
organized to fit the needs of the applications using the dataset.
In OTASP/OTAPA over ACAP, data on the server is organized to both
take advantage of ACAP capabilities and to use items that are
identical to IS-683A, allowing for reuse of IS-683A handset engines.
ACAP servers also support data inheritance. All data items which
are physically in the inherited dataset and not in the inheriting
dataset logically also exist in the inheriting dataset. This is
recursive, as the inherited dataset can itself inherit from another
dataset. This powerful concept allows potentially large groups of
mobile stations to inherit items from a single common entity. For
example, preferred roaming lists can be stored in datasets based on
geographic areas, and automatically inherited by an individual
mobile station in that area. The roaming lists could be further
subdivided, for example based on tiers of free NVRAM in the mobile.
The mobile client need not be aware of this; it happens entirely on
the server.
ACAP uses trees to provide the data hierarchy. These data trees can
be viewed as similar to the directory/file structure used with all
common operating systems. The built-in inheritance mechanism,
together with the hierarchical structure, makes it extremely easy to
update general data without disturbing specific data.
Datasets exist within the user, group, and host hierarchies. The
user hierarchy holds datasets which belong to individual users. The
group hierarchy holds datasets which belong to groups (for example,
the "Region." groups in section 5.1.6.3 Server Roaming Lists). The
host hierarchy holds datasets which are for specific machines or
systems.
In addition to providing customizable data trees, ACAP also provides
several standard datasets for all clients. There is a capabilities
dataset that contains information on custom functionality and
enhanced features available to a specific client or at the site
generally. This allows a server to advertise any protocol
extensions, specialized attribute handling, or other enhanced
functionality it supports. A client that needs to use these
features can thus easily determine what is available before trying
to use them.
5.1.5.1. Structure
We divide the data accessed by the client into provisioning items,
group items, and client state items. Provisioning data contains NAM
items and requested-data items. Group items (such as preferred
roaming lists), are not specific to any mobile device. Group items
physically exist in their own datasets, but through inheritance
logically appear in client datasets.
The mobile stations always read data from provisioning entries and
write data to client state entries. This structure makes both
mobile clients and server configuration easy and simple, while
allowing for extensive custom and diagnostic capabilities.
5.1.5.2. Conventions
"" This signifies the empty string (used here for ACAP entries).
~ This is shorthand for "user/<userid>". It is part of the ACAP
protocol.
5.1.5.3. Dataset
Provisioning information is located in the "OTAP" dataset class.
(The full specification of this dataset will be published in a
subsequent document.) The prefix "Provision." is used for items that
are to be downloaded to the mobile, and the prefix "Client." is used
for items which the client stores on the server.
Provisioning data within the OTAP dataset is organized as a series
of items, each of which is stored in its own entry. The entry name
is the item name, and the "OTAP.VALUE" attribute contains the item
value. This structure permits change notification on a per-item
basis.
We chose the "Provision" and "Client" names to simplify various
operations. For example, the mobile client can easily download all
changed provisioning items by performing a search which returns the
"OTAP.VALUE" attribute of all entries whose name begins with
"Provision" and whose modtime is greater than the last time the
client retrieved data. An administrative client can easily generate
a report of all clients which have not received the most recent
update by searching for all entries named "Client" whose
"OTAP.modtime" attribute is less than the desired value.
A partial list of items follows.
5.1.5.4. Entries and Attributes
dataset.inherit
This is a standard ACAP attribute that identifies the location of
inherited data. It exists in the "" entry (the entry with the empty
name) within each dataset.
5.1.5.5. NAM Records
The OTAP dataset class contains an entry for each provisioned
mobile. The standard location for provisioning records is:
/OTAP/USER/<esn>/<nam>/
This tree format allows multiple NAMs per ESN. The specific entries
contain data in IS-683A parameter block types.
For example, the CDMA NAM would be stored in an entry called:
/OTAP/USER/<esn>/<nam>/Provision.CDMA-NAM/
The entries below show how NAM records would be organized on the
ACAP server:
CDMA/Analog NAM
Entry-Path: /OTAP/USER/<esn>/<nam>/Provision.CDMA-AMPS-NAM/
OTAP.Value: {17} xx xx xx ... xx
The CDMA/Analog NAM entry from IS-683A (section 4.5.2.1)
consists of at least 129 information bits, depending on the
number of SID NID list entries. This is stored as 17 (or more)
octets of binary data (padding is used to ensure an integral
number of octets).
Mobile Directory Number
Entry-Path: /OTAP/USER/<esn>/<nam>/Provision.MOBILE-DN/
OTAP.Value: {10} nnnnnnnnnn
The Mobile Directory Number from IS-683A contains BCD-encoded
digits representing the phone number. This is stored as a
string of 10 or more ASCII digits, e.g., "6195551212".
CDMA NAM
Entry-Path: /OTAP/USER/<esn>/<nam>/ Provision.CDMA-NAM/
OTAP.Value: {13} xx xx xx ... xx
The CDMA-NAM entry from IS-683A (section 4.5.2.3) consists of at
least 100 information bits, depending on the number of SID-NID
list entries. This is stored as 13 (or more) octets of binary
data (padding is used to ensure an integral number of octets).
IMSI_T
Entry-Path: /OTAP/USER/<esn>/<nam>/ Provision.IMSI_T/
OTAP.Value: {7} xx xx xx xx xx xx xx
The IMSI_T entry from IS-683A (section 4.5.2.4) consists of 55
bits of information in five fields. This is stored left-
justified in 7 octets of binary data.
5.1.5.6. Server Roaming Lists
The ACAP Server will have an entry for each different roaming list
configuration for a carrier. The example below assumes that the
desired differentiation for the roaming list is geographic, with
subdivisions for tiers of mobile free NVRAM It shows that for each
region there exists a set of roaming lists per free NVRAM range.
Note that a carrier can easily implement different or further
differentiation (e.g., by phone vendor or product type) by simply
changing the dataset tree and assigned the appropriate value to the
"dataset.inherit" attribute in the provisioning records.
/OTAP/GROUP/region.NorthEast/free-nv.128-512/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.NorthEast/free-nv.512-1024/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.SouthEast/free-nv.128-512/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.SouthEast/free-nv.512-1024/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.NorthWest/free-nv.128-512/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.NorthWest/free-nv.512-1024/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.SouthWest/free-nv.128-512/
preferred.roaming.list/OTAP.Value
/OTAP/GROUP/region.SouthWest/free-nv.512-1024/
preferred.roaming.list/OTAP.Value
5.1.5.7. Requested-Data Record
Inside the OTAP dataset is an entry with the name
"Provision.Requested-Data", which contains one attribute called
"OTAP.Requested-Data". This attribute is multi-valued. It is
either NIL or contains a list of strings. Each string is the name
of one element of data that the server requests the client to
supply.
After authenticating, the ACAP client issues a SEARCH command to
retrieve the values of the "OTAP.Requested-Data" attribute of the
"Provision.Requested-Data" entry. The client processes the returned
values (if any) by issuing a STORE command to set one or more
attributes in the "Client" entry. The value of each attribute is
either the corresponding mobile value (which may be an empty string
if the item has no value), or the special value "[N/A]" if the item
does not exist or is unknown on the mobile.
This mechanism is quite general, and can be used in the normal OTASP
case to modify the mobile"s dataset as appropriate for the condition
of the mobile. For example, the inheritance could be set based on
the amount of NVRAM available, to cause one set of preferred roaming
list data or another to be used. This mechanism can also be used in
other situations, such as to retrieve a complete set of mobile
configuration parameters for diagnostic reasons.
5.1.5.8. Sample Server Entry
The entry below is an excerpt of a sample ACAP server dataset entry
for a single mobile station, with an ESN of FB9876E and using NAM 1:
/OTAP/USER/FB9876E/1/
entry = ""
dataset.inherit = "/OTAP/GROUP/region.NorthEast/
free-nv.128-512/preferred.roaming.list/
OTAP.Value/"
entry = "Provision.Requested-Data"
OTAP.Requested-Data = ("Phone-Make" "Phone-Model" "SW-Rev"
"Free-NVRAM")
entry = "Client"
OTAP.Phone-Make = "Qualcomm"
OTAP.Phone-Model = "pdQ1900"
OTAP.SW-Rev = "001.030.0908"
OTAP.Free-NVRAM = "65536"
OTAP.Last-Modtime = "199812181703"
entry = "Provision.Mobile-DN"
OTAP.Value = {10} 619 555 1234
entry = "Provision.CDMA-NAM"
OTAP.Value = {13} xx xx xx xx xx xx xx xx xx xx xx
xx xx
This dataset shows not only provisioning data which was downloaded
into the mobile station, but also the items of client data requested
by the server (the Requested-Data attribute) and the values of those
items (the "Client" entry). It also indicates that the mobile
client successfully stored the values associated with the modtime
"199812181703". In addition, it shows that this client inherits
data (i.e., roaming lists) from the "NorthEast" region.
5.1.6. Administrative Client
The administrative client loads initial provisioning information
into the server, including specifying the roaming list to inherit.
The administrative client also updates provisioning server records
as needed, and retrieves data for reports (such as a list of clients
which have not yet been updated).
Data is loaded into provisioning records by using the ACAP STORE
command. The administrative client authenticates to the ACAP server
using credentials that permit access to datasets for mobiles.
When a new mobile is authorized for service, the administrative
client creates the dataset by storing into it values that are
specific for the device. It also sets the "dataset.inherit"
attribute so that values which are not tied to the specific mobile
are inherited as appropriate.
* Updates to user records
Existing user records may need updating from time to time. For
example, a user may change service plans or purchase an
additional or replacement mobile device, or the carrier may
need to modify some aspect of provisioned data.
* Perusal and editing of provisioning records
The administrative client can provide general browse and edit
capability for user records.
* Report generation
The administrative client can extract data from the ACAP server
in order to generate reports. For example, after OTAPA
activity, a carrier may wish to identify those mobiles which
have not yet been updated.
* Queuing of OTAPA sessions
Depending on the OTAPA update procedures chosen (e.g., SMS,
CLID, periodic recheck), the administrative client may be
involved in initiating the activity. This may or may not use
an interface to the provisioning server.
5.1.7. Mobile Client
The ACAP mobile client is implemented as a state machine that
performs the equivalent of IS-683A provisioning parameter
information exchange and non-volatile memory storage. The ACAP
Client state machine diagram (Figure 2) and descriptions are below.
[Figure 2 -- see PostScript version]
* Establish Transport Layer/Authenticate
Authentication and/or encryption can occur at the application
layer and/or at the network/transport layer.
Basic ACAP authentication occurs in the application layer
(i.e., within the ACAP session), and in its baseline form uses
the CRAM-MD5[CRAM-MD5] mechanism. If desired, other mechanisms
can be used which provide more protection and encryption. This
occurs after the transport layer is established, as shown in
the client state machine diagram above
Figure 3 shows the CRAM-MD5 authentication mechanism for an
unprovisioned mobile. In the case of provisioned mobiles, the
shared secret is derived from the A-Key, instead of the
limited-time N-digit code used for unprovisioned devices.
Use of basic ACAP authentication is preferred for initial
implementations of data-OTASP because it is simple, easy to
implement, and all procedures and methods are in place.
Stronger SASL mechanisms and/or IPSec can be rolled out in the
future without disrupting the deployed base.
[Figure 3 -- see PostScript version]
* Requested-data SEARCH
The mobile ACAP client issues a search command aSKINg the
server to return the attribute "OTAP.Requested-Data" in the
entry "Requested-Data".
* Receive requested-data values
The server instructs the client to store attributes by
returning one or more values of requested-data in response to
the Requested-Data SEARCH.
For example, the attribute "OTAP.Requested-Data" in the entry
"Requested-Data" might contain four values: "phone-make",
"phone-model", "SW-Rev", and "Free-NVRAM".
* STORE attribute list
If the response to the requested-data SEARCH returns any
values, the client issues a STORE command. Each attribute in
the STORE command corresponds to one item of requested-data.
If the client does not recognize an item, it stores the string
"[n/a]".
Continuing with our example, the client uses this STORE command
to write four attributes into the "Client" entry. Each
attribute name is identical to one value of the
OTAP.Requested-Data" attribute (with the prefix "OTAP." added).
Each attribute value is determined by the respective mobile
value.
In our example, this STORE command sets the following
attributes and values:
- "OTAP.Phone-Make" = "Qualcomm
- "OTAP.Phone-Model" = "pdQ1900
- "OTAP.SW-Rev" = "001.030.0908"
- "OTAP.Free-NVRAM" = "65536"
* Provisioning data SEARCH
The mobile ACAP client issues a search command to retrieve any
items of provisioning data that have changed since it last
checked in (which in the initial session retrieves all
provisioning data).
This SEARCH command asks the server to return the "OTAP.Value"
attribute of any entries whose name starts with "provision."
(case-insensitive) and whose modtime is greater than the
supplied value (which is zero for an unprovisioned mobile).
* Receive provisioning data and modtime
The server returns the provisioning items, each as one entry
name and one attribute value. The server response to the
SEARCH command includes the modtime of the latest entry
returned.
* Save values
The mobile writes the returned values into NVRAM.
* STORE modtime
The ACAP client stores the returned modtime on the server as an
acknowledgement that the data was received and NVRAM updated.
* LOGOUT
The client issues the LOGOUT command.
* Close transport layer
The client closes the TCP connection.
* End call
The data call is terminated.
5.2. WAP with ACAP
An advantage of the ACAP solution is that is can easily coexist with
a WAP-based mechanism, giving carriers more options.
A carrier can deploy handsets into its service area which use WAP-
based provisioning, if desired, alongside those which use ACAP
provisioning. All that is required is that the WAP server contain a
small ACAP client (or an interface to an ACAP server).
Figure 4 shows how mobile stations can be configured using a WAP
browser. By using an ACAP server for provisioning, carriers are
free to simultaneously deploy mobile stations that use either WAP or
ACAP, as desired. In either case, the ACAP server is the source for
provisioning data.
[Figure 4 -- see PostScript version]
5.3. Network-Resident vs. Configuration Data
It is useful to recognize that wireless devices access two different
types of carrier-provided data: network-resident and configuration.
Network-resident data exists primarily within the carrier"s network.
Examples include account status, billing detail, service plan
options, etc. While mobiles may access this information for user
display, it resides in the network. Configuration data, in
contrast, affects the operation of the handset, is usually not shown
to the user, and must persist in the device.
For network-resident data access, the obvious choice is the web.
The data is highly interactive and time-variant, making web browsers
a reasonable solution. Any appropriate web browser can be used.
There are many good reasons for having a web browser in a wireless
device which contains a display and is capable of user interaction.
For configuration data, the best solution is to use ACAP. ACAP is
optimized for the job, can be implemented quickly, requires a very
small amount of memory, and does not depend on a display or any user
interaction capability.
Trying to use the same access method for both types of data
unnecessarily complicates the solution, leading to increased design,
development, and debug time and expense. It makes it more difficult
to offer low-cost devices. Since the two types of data
fundamentally differ, it is good engineering practice to select
optimal code and protocols for each.
5.4. Intellectual Property Issues
There are no known intellectual property issues with the ACAP
solution. The ACAP specification was developed within the IETF, and
no ownership, patent, or other IP claims have been asserted.
Multiple independent vendors are developing ACAP clients and
servers, in addition to the existing usage in deployed products.
6. Handset Protocol Suites
6.1. ACAP over TCP/IP
Figure 5 depicts the mobile station protocol suite for the ACAP over
TCP/IP solution. The mobile station is capable of supporting both
IS-683A OTASP and OTASP over ACAP.
[Figure 5 -- see PostScript version]
7. IS-683A Compatibility
7.1. OTASP Operations
To maximize compatibility and allow for reuse of IS-683A handset
code, the data formats used in OTASP over ACAP are identical to
those used in IS-683A. Section 5.1.5 Data Organization and
Capabilities discusses this in more detail.
OTASP via IS-683A requires custom design and development for the
specific CDMA infrastructure used by a carrier. This can greatly
limit the data management capabilities and significantly reduces the
extensibility of the solution. Conversely, OTASP over data can be
implemented on a generic IP network using an Internet standards-
based capability that provides extensible provisioning activities
for carriers.
OTASP over data uses a traffic channel whereas IS-683A OTASP runs
over the limited-bandwidth signaling channel.
IS-683A OTASP operations are inherently simultaneous voice and data.
This allows the customer care representative to extract information
from the mobile station while conversing with the user. OTASP over
data services is a data-only solution (at least for now). This
makes OTASP operations slightly more sequential and potentially
problematic. Simultaneous voice and data will alleviate this issue.
7.2 OTASP Call Flow
The call flow diagram (Figure 6) depicts the message sequence and
operations for a typical IS-683A OTASP (provisioning) call. Any
data-OTASP solution must perform all the functions of the IS-683A
OTASP call. The proposed solution meets these requirements.
[Figure 6 -- see PostScript version]
7.3. OTAPA Operations
Data-OTAPA requires the ability to instruct mobiles to originate a
data call to the provisioning server. Several viable approaches are
discussed in sections 3.3 OTAPA Activity and 4.3 OTAPA
Requirements.
OTAPA over data has the potential to require far less channel
resources to download new information to mobile stations. The ACAP
server inherently only communicates changes to the clients, thus
only changed information needs to be downloaded to the mobile
stations using OTAPA over data via ACAP.
7.4. OTAPA Call Flow
The call flow diagram (Figure 7) depicts the message sequence for a
typical IS-683A OTAPA operation. Any data-OTAPA solution must
perform all the functions of the IS-683A OTAPA call. The proposed
solution meets these requirements.
[Figure 7 -- see PostScript version]
8. Alternative Methods
8.1. IS-683A over TCP/IP
One alternative is to port IS-683A to TCP, remaining as close as
possible to the IS-683A protocol exchange.
Figure 8 depicts the architecture and communications backbone to
support OTASP/OTAPA via IS-707 data services with a provisioning
server based on the IS-683A OTAF function.
[Figure 8 -- see PostScript version]
8.1.1. OTAF Server
This provisioning server is modeled after the IS-683A OTAF. The
OTAF server performs the specific operations and messaging of IS-
683A OTAF. This includes A-key reauthentication procedures.
Strongpoints:
(1) OTAF and mobile station behavior mirrors IS-683A (reduced
duplicate software in mobile station). Nearly all procedures fully
defined.
Drawbacks:
(1) The OTAF server would need to be custom-designed and built.
(2) No inherent data manipulation capabilities in the OTAF server.
All required or desired data management activities would have to be
built from scratch.
(3) Interface application would require a non-standard interface
(and therefore proprietary) to OTAF server.
(4) End-to-end encryption scheme still needed for full security.
8.1.2. Interface Application
This function loads all required provisioning-related information
from the CDMA network information system to the OTAF server. This
includes the queuing of provisioning transactions and data.
8.1.3. Protocol Handset Suite
Figure 9 depicts the mobile station protocol suite for the IS-683A
over TCP/IP solution. The OTASP client is capable of supporting
both IS-683A OTASP activities or OTASP activities over the data
transport.
[Figure 9 -- see PostScript version]
8.2. Browser-Based Forms
Another alternative is to use forms embedded in web pages.
Encapsulating the provisioning data into custom tags embedded in a
web form is an idea that at first seems attractive. There are a lot
of advantages in having a browser in the handset, web servers are
very widely deployed, and everyone is familiar on some level with
the web.
However, a meta-protocol for this would need to be designed, and a
fully detailed specification produced. This solution requires
custom software on the provider side to handle the meta-protocol.
It additionally requires handset vendors to add custom software in
the handset browser to handle this protocol.
This solution would require a provisioning-capable browser in every
phone. While it may be desirable to have a browser, the decision to
require it needs to be considered carefully, especially in light of
the memory requirements it would impose on all devices.
This solution would complicate the handset browser, by requiring it
to handle provisioning as well as browsing. As provisioning and
browsing are functionally dissimilar, this code is not a natural fit
within the browser. Implementing this solution would require a
significant increase in development and debug resources, and thus
negatively impact time-to-market and cost.
Also because the web is functionally dissimilar, a high level of
carrier-side customization would be needed, leading to reduced
vendor choice and increased deployment costs.
This approach would layer custom data on top of a standard protocol.
This would require design work, and would not have much time for
open review before deployment, greatly increasing the risk. By
contrast, ACAP has had years of open review and refinement.
This approach also limits the extensibility of the solution. ACAP,
conversely, is very extensible. Because ACAP is such a simple
protocol, it can be added to a wide variety of applications at low
cost. This allows increasing numbers of applications on the mobile
device to share information with servers as well as desktop
applications.
9. Conclusion
ACAP provides a high degree of extensibility, especially in
authentication mechanisms, custom attribute handling, and data
management. By using an Internet standard protocol,
interoperability and integration with a variety of equipment is
possible, and carriers are not locked into any vendor. It is also
easier to add new levels of service and capabilities, especially
integration with future subscriber devices and applications (e.g.,
email).
Since an ACAP client is so small, it can be incorporated into
virtually any device, even low-end ones without displays, and can be
added without sacrificing other features. The simplicity of the
client and protocol directly translate to shorter development cycles
and faster time-to-market.
Because the ACAP protocol was designed for precisely this type of
provisioning activity, its adoption can greatly reduce the cost,
time to market, and support required for the provisioning server as
well as the handsets. As an open standard, the ACAP protocol has
benefited from years of review and experience.
Another advantage of the ACAP solution is that is can easily coexist
with a WAP-based mechanism, giving carriers more options and
reducing the minimal requirement burden on mobile devices.
A carrier can deploy handsets into its service area which use WAP-
based provisioning, if desired, alongside those which use ACAP
provisioning. By using an ACAP server for provisioning, carriers
are free to simultaneously deploy mobile stations that use either
WAP or ACAP, as desired.
The lack of intellectual-property issues further adds to ACAP"s
appeal.
10. References
[ACAP] Newman, C. and J. Myers, "ACAP -- Application
Configuration Access Protocol", RFC2244, November 1997.
[CRAM-MD5] Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP
AUTHorize Extension for Simple Challenge/Response", RFC
2195, September 1997.
[SASL] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC2222, October 1997.
11. Security Considerations
Security is discussed in many sections of this document. In
particular, the need and methods to guard against unauthorized
updating of handsets, usurpation of newly-created accounts,
compromise of handset security values, and disclosure of carrier
proprietary data and handset parameters is covered.
12. Acknowledgments
Jim Willkie and Marc Phillips contributed greatly to this document.
Their help is very much appreciated.
13. Author"s Address
Randall Gellens
QUALCOMM Incorporated
6455 Lusk Boulevard
San Diego, CA 92121-2779
Phone: +1 619 651 5115
EMail: randy@qualcomm.com
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