RE: [dhcwg] Revised charter

> Can you give us more details?  What problems would we
> consider as part of mobility support in DHCP?

Well, I think it's not problem but restriction in DHCP. 
I guess current DHCP architecture is not concretely 
matched to the mobility because of long round-trips 
to get IP address and related information. Above all 
DHCP is a natural choice in the Wireless Lan (802.11) 
in conjunction with Access Point (AP), thus I think it's 
worth discussing this with dhc folks.

It's [Introduction] [Background] [Design Goals]
sections of preparing draft for your information and it 
will be available soon.

Hope this helps.

1. Introduction 

The world has become increasingly mobile. As a result,
traditional ways of networking the world have proven 
inadequate to meet the challenges posed by our new 
collective lifestyle.  Wireless technology has been 
successful because it enables people to connect with each
other regardless of location and the most successful 
wireless networking technology this far has been 802.11 
WLAN [802.11][WLAN]. 

Regarding the wireless technology, DHCP [RFC 2131] 
is widely used for obtaining the network configuration on
the mobile node such as its unique IP address and others
in the local networks.  DHCP is useful with access point 
which generally includes a DHCP server because it 
minimizes mobile node configuration.  The DHCP server 
(access point) can be allocated a pool of addresses.  The 
administrator specifies both the DHCP based address and 
the size of the pool.  The DHCP server (access point) can 
also be configured to hand out a default gateway and DNS 
server information. 

The main objective of this draft is to propose a new architecture
of DHCP to support the mobility on the DHCP client as mobile 
node.  Also fast network attachment mechanism should be 
considered in conjunction with the mobile IP [RFC 3220] [MIP6] 
which allows a mobile node to move from one link to another 
without changing the mobile node's "home address".  Packets 
may be routed to the mobile node using this address regardless
of the mobile node's current point of attachment to the Internet.  
The mobile node may also continue to communicate with other
nodes (stationary or mobile) after moving to a new link.  The 
movement of a mobile node away from its home link is thus 
transparent to transport and higher-layer protocols and 
applications. 

The aim of this draft is neither network information such as 
DNS nor fast handover mechanism [FH802.11]. 

3. Background 

The aim of this draft is to discuss mobility issue in the
DHCP environment and it is especially appropriate for 
processes and devices which already interpret DHCP
messages.   

In particular, a new proposed architecture allow DHCP 
server to send available IP addresses to DHCP client 
quickly to attach a new network when in motion. 

Placing DHCP server on the access point is a natural 
choice in the 802.11 wireless environment. 

The Unsolicited message is an extension to the DHCP 
protocol. 

The main purpose of this draft is to provide a starting 
point of mobility issue in the DHC Working Group. 

4. Design Goals 

The goal of this draft is to provide a lightweight mechanism
for supporting mobility in the DHCP environment.  It is 
designed to optimize current DHCP mechanism to cut 
down number of round-trips between DHCP client and 
DHCP server. 

Here are some requirements why this design is required. 

[1] Wireless technologies especially 802.11 are widely 
spread in the DHCP environment, thus fast network 
attachment is importantly required on the DHCP client 
when in motion. 

[2] Current 4-messages exchange is not matched for
the mobility. 

[3] Effectively this design aims outperforming rapid 
commit technique by substituting the explicit DHCP 
operation with the implicit link-layer association event. 

[4] DHCP server functionality is common on the access
point. 

[5] For supporting mobility on the current DHCP protocol, 
minimal additional configuration/requirement is required. 

- Daniel (Soohong Daniel Park)
- Mobile Platform Laboratory, SAMSUNG Electronics. 

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