DHC Working Group
Internet Draft Murali Achanta
Document: draft-achanta-dhc-ap-options-00.txt Cisco Systems
Expires: December 2005 June 2005
DHCP Option for Radio Configuration Parameters to Mobile Access
Points
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Copyright Notice
Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract
This document defines a DHCP option that contains Radio specific
Parameters for Mobile Access Points, Like Transmit Power, Country
code, reserved RF channels.
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Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [i].
Table of Contents
1. Motivation.....................................................2
2. Mobile access point radio Configuration parameters option format3
2.1 Radio transmit power sub-option............................3
2.2 Radio IOS 3166 country code sub-option.....................3
2.3 Radio reserved RF channels sub-option......................4
3. IANA Considerations............................................4
4. Security Considerations........................................4
References........................................................4
Acknowledgments...................................................5
Author's Addresses................................................5
1. Motivation
Dynamic Host Configuration Protocol provides necessary mechanism for
device configuration. However, there is no provision for Mobile
access points to get their radio configuration information elements.
With Introduction of portable mobile Access points, users can take
these mobile access points along with them where ever they go to
extend wired network to wireless network. Problem is when multiple
users take multiple access points to a Motel then there will be
overlapping radio cells, because one radio cell may go across
multiple motel rooms. One way to solve this problem is to configure
lower transmit power levels on these access points. However users
will not proactively configure lower transmit powers on their access
points. 802.11h TPC is only to control transmit power of 802.11
clients not for the access points. We need a way to automatically set
the transmit power from wired network, that way network admin can
configure lower transmit powers to decrease the radio cell size
depending on the room sizes, so that multiple rooms can have their
own cell without interfering other radio cells.
Mobile access points may get radio specific configuration parameters
for this network from DHCP server, to determine what is the max
transmit power allowed, which country this mobile portable access
point has been plugged into, what are the recommended RF channels not
to be used while connected to this network.
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2. Mobile access point radio Configuration parameters option format
The option begins with a tag octet containing the option code(TBD). A
length octet following the tag octet. The value of the length octet
does not include itself or the tag octet. This option layout is
depicted below:
+------+--------+--------------+--------------+---+--------------+
| TBD |Length | Sub-option 1 | Sub-option 2 |...| Sub-option n |
+------+--------+--------------+--------------+---+--------------+
A sub-option begins with a tag octet containing the sub-option code.
A length octet follows the tag octet. The value of the length octet
does not include itself or the tag octet. The length octet is
followed by "length" octets of sub-option information. The sub-ption
layout is depicted below:
+-------------------+--------+------------------------+
| Sub-option Code | Length | Sub-option information |
+-------------------+--------+------------------------+
2.1 Radio transmit power sub-option
This sub-option provides a Max allowed Transmit power in unit of dBm.
It is a one octet value.
Code Len 802.11 wireless transmit power
+-----+-----+---------------+-----
| 1 | 1 | power in dBm |
+-----+-----+---------------+-----
2.2 Radio IOS 3166 country code sub-option
This sub-option provides the country code of the network in which
this mobile access point is connected to. This information MUST be
used to derive the RF channel list this access point is supposed to
operate as per regulatory requirements.
Code Len 802.11 wireless A2 IS0 3166 country code
+-----+-----+-----+-----+-----+-----+--
| 2 | 2 | c1 | c2 |
+-----+-----+-----+-----+-----+-----+--
County code values are to be taken from valid ISO 3166 standard.
Alpha-2 code elements MUST be used in this option. c1 and c2 are the
two characters for a given country code.
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http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-
lists/list-en1.html
2.3 Radio reserved RF channels sub-option
This sub-option provides a list of channel a mobile access point not
supposed to operate in order to avoid interference to the native
devices operating in the network.
Code Len 802.11 wireless reserved channels
+-----+-----+----------+-----------+----------+---
| 3 | n | channel1 | channel2 | channel3 | . . . . .
+-----+-----+----------+-----------+----------+---
Channel[1..n] is 4 digit representation of the radio frequency in
MHz. Example: 2412 MHz, 2462 MHz, 5180 MHz.
3. IANA Considerations
IANA is requested to assign an option code for radio configuration
parameters for mobile access points.
4. Security Considerations
These DHCP options may be used by intruder DHCP server to mislead the
mobile access points to operate in country domain other than the
existing country and provide wrong power levels.
References
[1]Bradner, S., "Intellectual Property Rights in IETF Technology",
BCP 79, RFC 3668, Feb. 2004
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
[3] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
1997.
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Acknowledgments
Author's Addresses
Murali Achanta
Cisco Systems, Inc.
170 W Tasman Drive
San Jose, CA 95134, USA
Email: achanta@cisco.com
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