W2LAN: Wireless 2 LAN protocol

Section: Linux-W2LAN Manual (8)
Updated: December 15, 2007
Index  

NAME

w2lan - a protocol that transforms a wireless ad-hoc Ethernet network into a LAN  

SYNOPSIS



w2lan [options] interface
 

DESCRIPTION

w2lan is a protocol that provides layer 2 routing for wireless Ad-Hoc Ethernet networks. The effect is the elimination of the partial visibility problem that MANET networks exhibit.

Part of the parameter check consist on making sure that w2lan is running on a 802.11 wireless Ad-Hoc Ethernet interface. Although the protocol can operate in any Ethernet network, it is only in Ad-Hoc networks where the partial visibility problem shows, hence w2lan proves useful (maybe in futures versions it can be an option for testing/developing purposes, since not every PC has a wireless adapter, and most have Ethernet -or at least a loopback-).

w2lan splits each Ethernet frame into 3 new Ethernet frames: w2lan announce (34 bytes), w2lan request (20 bytes) and w2lan data (the same size than the original Ethernet frame).

A node executing w2lan, reacts when a reception of a w2lan frame occurs:

If a w2lan announce frame is received, the node checks if such conversation has been handled before. In the case it is a new conversation, the node updates its conversations list and it sends the corresponding w2lan request frame.

If a w2lan request frame is received, the node checks if he has announced such conversation. If that is the case, a request counter is updated accordingly.

If a w2lan data frame is received, the node checks if he has requested such conversation. If that is the case, the original Ethernet frame is reconstructed with the recently received w2lan data frame and the previously received w2lan announce frame. Next, the newly reconstructed Ethernet frame is announced, and if the Ethernet frame destination field is either for the node, multicast or broadcast, the frame is injected to the network (to be used by the node protocol stack). After a certain time, specified in "w2lan.h" by TIMEOUT_REQUEST_SECONDS, the node will check the counter associated with the newly announced frame, and if there is any interest (counter different of 0) the corresponding w2lan data frame will be generated.
     Also, a node executing w2lan in "always" mode or sometimes in "reactive" mode (see the OPTIONS section), when it sends an Ethernet frame, it also sends a corresponding w2lan announce frame, that consist on a w2lan announce header plus a payload consisting on a new conversation ID plus the header of the previously sent Ethernet frame. In a certain time, specified in "w2lan.h" by TIMEOUT_REQUEST_SECONDS, the node might receive w2lan requests frames from its neighbours. If that is the case, the node proceeds by sending a w2lan data frame, consisting on a w2lan data header, which includes the conversation ID field, plus the payload of the previously sent Ethernet frame.
   

OPTIONS

w2lan has 3 modes of operation, depending on the characteristics of the underlying node. The modes are: passive, reactive and always (default for linux). In passive mode, the node executing w2lan does not generate any new conversations. The node simply relies existing conversations. In always mode, the node executing w2lan does rely existing conversations, plus it generates a new conversation every time the node has an Ethernet frame to send. Reactive mode is an hibrid between passive and always. It starts behaiving like in always mode, but after a number of frames (specified by MAX_NON_W2LAN_FRAMES) of w2lan traffic absence, the node switches to passive behaviour. The node is switched back to active when w2lan traffic reapears.

-m passive      The node operates in passive mode
-m reactive    The node operates in reactive mode (default)
-m always              The node operates in always mode


 

EXAMPLES

bash# w2lan -m always eth2
It start executing the w2lan protocol on the eth2 interface. eth2 has to be a wireless ethernet interface in Ad-Hoc mode. This command is advised to be used in a server node (i.e. node that serves DHCP+NAT).
bash# w2lan -m reactive eth2
It start executing the w2lan protocol on the eth2 interface. eth2 has to be a wireless ethernet interface in Ad-Hoc mode. This command is advised to be used in a client node (i.e. node that access the Internet through NAT).
bash# w2lan -m passive eth2
It start executing the w2lan protocol on the eth2 interface. eth2 has to be a wireless ethernet interface in Ad-Hoc mode. This command is advised to be used in a helper node (i.e. node that has no users on it, but helps increase the coverage area).

 


DOWNLOAD

Here the W2LAN Linux version (Windows version available soon...)

Source code:
W2LAN source code (tar.gz) download (version 0.1)


DEB Binary (Intel 32bits):
w2lan_0.1-2_i386.deb

RPM Binary (Intel 32bits):
w2lan-0.1-1.i586.rpm

RPM Binary (Intel 64bits):
w2lan-0.1-1.x86_64.rpm


 

AUTHOR

Francesc Burrull i Mestres - francesc.burrull@upct.es

Universidad Politecnica de Cartagena - http://www.upct.es


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
AUTHOR

Time: 10:55:18 GMT, December 17, 2007