Internet DRAFT - draft-hong-dna-if-l2
draft-hong-dna-if-l2
DNA Working Group Yong-Geun Hong
INTERNET DRAFT Jung-Soo Park
Expires: April 2005 Hyoung-Jun Kim
ETRI
October 2004
Considerations for DNA Schemes with Multiple Interfaces
and Layer 2 Technologies
<draft-hong-dna-if-l2-00.txt>
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Abstract
In this document we consider and analyze various environments for
applying Detecting Network Attachment (DNA) schemes. Although DNA
schemes are typically run for each interface and a host separately
checks for link changes on each interface when the host has
multiple interfaces, DNA schemes in the host must be considered to
check the multiple interfaces at the same time for a seamless
service. In addition, DNA schemes in the host must be capable of
managing together each DNA scheme on each interface. Current DNA
schemes only rely on "Break before Make" L2 technology such as
802.11. But now and in future, there will be other "Make before
break" L2 technologies such as CDMA. In these L2 technologies, DNA
schemes must be operated differently in order to make use of their
characteristics.
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Table of Contents:
1. Introduction................................................2
2. Terminology.................................................3
3. Various cases with Interfaces and Layer 2 Technology........3
3.1 Case : Single Interface with Break before Make.............4
3.2 Case : Single Interface with Make before Break.............4
3.3 Case : Multiple Interfaces with Break before Make..........4
3.4 Case : Multiple Interfaces with Make before Break..........5
4. Security Considerations.....................................5
5. Acknowledgments.............................................5
6. References..................................................6
Author's Addresses.............................................6
1. Introduction
In fixed wire networks, when communication failure happens, it is
expected that there are physical or link-layer errors. Change of
the link-layer seldom happens. But in wireless and mobile networks,
communication failures are caused by many reasons. Not only
physical errors, but also the out of range of Access Point coverage
and movement between networks (links) are important factors for
communication failures.
Detecting Network Attachment (DNA) is proposed for solving the
above problem, for movement between networks (links). To do this,
DNA schemes detect the identity of the currently attached link to
ascertain the validity of the existing IP configuration [3].
DNA schemes are typically run for each interface and a host
separately checks for link changes on each interface when the host
has multiple interfaces [3].
In future ubiquitous networks, many services and various
technologies are expected to be inter-worked and harmonized for a
better and seamless service. Wired and wireless technologies are
expected to be coupled and it is the same for different wireless
technologies. As various wireless technologies are introduced, a
host having multiple interfaces has appeared. The multiple
interfaces may be the same technology or a different technology
such as WLAN/CDMA, WLAN/GPRS. In this multiple interface host, DNA
schemes must be considered to check the multiple interfaces at the
same time for a seamless service and to manage together each DNA
scheme on each interface.
Current link-layer technologies which DNA schemes are operated on
are 802.3 Ethernet or 802.11 wireless LAN technologies. The
characteristics of these link-layer technologies are that a new
link-layer connection is made only after an old link-layer
connection is torn down. Also in these link-layer technologies, a
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host does not have any information about a new link until a new
link-layer connection is established. The only way to recognize
information about the new link is to receive link information (e.g.
Router Advertisement message) only after a new link-layer
connection is made [1,2].
Because other link-layer technologies such as CDMA have the ability
to make a new link-layer connection before an old link-layer
connection is torn down, a host may know new link information
before a new link-layer connection is established [7]. In these
link-layer technologies, current DNA schemes may not be the proper
solution to handle link change. It needs other features of DNA
schemes to support this characteristic.
This document identifies various cases for applying DNA schemes. We
consider and analyze various environments according to whether
multiple interfaces are supported and the characteristics of link-
layer technologies.
2. Terminology
This document identifies various cases for applying DNA schemes. We
consider and analyze various environments according to whether
multiple interfaces are supported and the characteristics of link-
layer technologies. Following are two typical characteristics of L2
technologies :
Break before Make
The characteristic of link-layer technology where a new link-
layer connection can be made only after an old link-layer
connection is disconnected. In this link-layer technology,
new link information can be acquired only after a new link-
layer connection is made, that is only after an old link-
layer connection is torn down.
Make before Break
The characteristic of link-layer technology where a new link-
layer connection can be made before an old link-layer
connection is disconnected. In this link-layer technology,
new link information can be acquired before a new link-layer
connection is made, that is before an old link-layer
connection is torn down.
3. Various cases with Interfaces and Layer 2 Technology
In this section, we classify cases for applying DNA schemes whether
a host has a single interface or multiple interfaces and whether
link-layer technology are Break before Make or Make before Break.
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3.1 Case : Single Interface with Break before Make
It is the typical case where we are currently using a 802.11
wireless LAN. In this case, a new link-layer connection is
established to a new access point only after an old link-layer
connection is disconnected. Two different link-layer connections
cannot be established simultaneously.
In this case, link information can be acquired only after a new
link-layer connection is established. Only after a new link-layer
connection is made, a host can collect the appropriate information
and detects the identity of its currently attached link to
ascertain the validity of its IP configuration [3].
In this case, the focus of DNA schemes is that how can a host
receive link information in a fast and effective method. To do
this, until now, there are many proposed mechanisms. [4,5,6]
3.2 Case : Single Interface with Make before Break
We think that we are not familiar with this case. But in CDMA[7], a
mobile station can access two or more different base stations
simultaneously. In this case, a host can make a new link-layer
connection before an old link-layer connection is torn down.
In this case, a host can acquire new link information through a new
link-layer connection before an old link-layer connection is torn
down. A difference from the above case (Section 3.1) is that a host
can acquire link information over a new link-layer connection while
keeping an old existing link-layer connection.
In this case, the focus of DNA schemes may be different from the
above case. We think that DNA schemes should have the ability to
handle this difference.
3.3 Case : Multiple Interfaces with Break before Make
As various wireless technologies are introduced, a host has a
chance to have multiple interfaces. Link-layer technologies of each
multiple interface may be the same (e.g. all of them are 802.11) or
different (e.g. one of them is 802.11 and one of them is CDMA /
GPRS)
If each link-layer technology of each interface is the same and
each interface is in the same link, this scenario may not be very
much different with case 3.1. Because each interface is in the same
link, link information on each interface may be the same. In this
scenario, multiple interfaces do not have any effect on detecting
any link changes.
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But, if each link-layer technology of each interface is the same
and each interface is in a different link (although this scenario
may not be common), a host must have the ability to manage each
interface and its link information on each interface. In this
scenario, when a host detects a link-layer change, it can use other
link information to support a seamless service, or the host can
follow general DNA schemes on the interface where a link-layer
change happens.
If each link-layer technology of each interface is different,
situations may be different from the above two scenarios. If each
interface is in the same link, one link-layer change on one
interface does not mean the link changes. The reason is that each
interface has different characteristics for its link-layer
technology (e.g. the service coverage area of each access point may
be different). Also each interface is in different links, one
link-layer change on one interface does not mean the link changes.
In these scenarios, a host must have the ability to manage each
interface and tis link information. There may be other
considerations to make use of these scenarios.
3.4 Case : Multiple Interfaces with Make before Break
If a host has multiple interfaces and each link-layer connection is
operated on the make before break method, DNA schemes may be
operated differently. Because a new link-layer connection can be
made before an old link-layer connection is disconnected and a host
has multiple interfaces, it can keep link information on another
interface in spite of a link-layer change of one interface.
In this case, we think that the scenario where each link-layer
technology of each interface is different may not exist. To support
the make before break method on multiple interfaces, each link-
layer technology must be the same.
4. Security Considerations
This document discusses considerations for applying DNA schemes on
various environments. The associated security issues will be
identified as further work goes on.
5. Acknowledgements
We would like to express our sincere appreciation to Do-Wan Kim,
Tony Bonanno for their valuable comments in improving this draft.
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6. References
Normative
[1] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[2] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
Informative
[3] Choi, J. and G. Daley, "Detecting Network Attachment in IPv6
Goals", draft-ietf-dna-goals-02.txt (work in progress),
September 2004.
[4] Choi, J. and D. Shin, "Fast Router Discovery with RA Caching
in AP", draft-jinchoi-mobileip-frd-00 (work in progress),
February 2003.
[5] Kempf, J., Khalil, M. and B. Pentland, "IPv6 Fast Router
Advertisement", draft-mkhalil-ipv6-fastra-02 (work in
progress), October 2002.
[6] Daley, G., Pentland, B. and E. Nordmark, "Deterministic Fast
Router Advertisement Options", draft-daley-dna-det-fastra-00
(work in progress), July 2004.
[7] TIA/EIA/IS-2000 Series, "CDMA 2000 Series, Release A (2000)"
Authors' Addresses
Yong-Geun Hong
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Phone: +82 42 860 6557
Email: yghong@pec.etri.re.kr
Jung-Soo Park
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Phone: +82 42 860 6514
Email: jspark@pec.etri.re.kr
Hyoung-Jun Kim
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Phone: +82 42 860 6576
Email: khj@etri.re.kr
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