NAME

aan − always available network

SYNOPSIS

­aan [ ­-d ] [ ­-c ] [ ­-m maxto ] ­dialstring | ­dir

DESCRIPTION

­Aan tunnels traffic between a client and a server through a persistent network connection.  If the connection breaks (voluntarily or due to networking problems), the aan client re-establishes the connection by redialing the server. 

­Aan uses a unique protocol to make sure no data is ever lost even when the connection breaks.  After a reconnection, ­aan retransmits all unacknowledged data between client and server. 

A connection can be broken voluntarily (e.g. by roaming over IP networks), or a connection can break when the IP service is unreliable.  In either case ­aan re-establishes the client’s connection automatically. 

When the server part has not heard from the client in ­maxto seconds, the server part of ­aan exits.  The default ­maxto is one day.  The client side (option -c) calls the server by its dialstring, while the server side listens for connections in the already-announced network directory devdir.

­Aan is usually run automatically through the ­-p option of import(4).

EXAMPLE

Assume the server part of aan is encapsulated in exportfs on the machine ­sob and started through ­aux/listen as follows:

netdir=‘{echo $3 | sed ’s;/[0-9]+$;!∗!0;’}
exec exportfs -a -A $netdir

Then machine astro6’s name space can be imported through ­aan using this command:

import -p astro6 / /mnt/term

FILES

­/sys/log/aan
Log file

SOURCE

­/sys/src/cmd/aan.c

SEE ALSO

import(4), exportfs(4)

Plan 9  —  February 17, 2003