.\" Copyright (c) 2012 Luigi Rizzo, Universita` di Pisa
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.\" This document is derived in part from the enet man page (enet.4)
.\" distributed with 4.3BSD Unix.
.\"
.\" $FreeBSD$
.\" $Id: $
.\"
.Dd July 27, 2012
.Dt VALE 4
.Os
.Sh NAME
.Nm vale
.Nd a very fast Virtual Local Ethernet using the netmap API
.Sh SYNOPSIS
.Cd device netmap
.Sh DESCRIPTION
.Nm
is a feature of the
.Xr netmap 4
module that implements multiple Virtual switches that can
be used to interconnect netmap clients, including traffic
sources and sinks, packet forwarders, userspace firewalls,
and so on.
.Pp
.Nm
is implemented completely in software, and is extremely fast.
On a modern machine it can move almost 20 Million packets per
second (Mpps) per core with small frames, and about 70 Gbit/s
with 1500 byte frames.
.Sh OPERATION
.Nm
dynamically creates switches and ports as clients connect
to it using the
.Xr netmap 4
API.
.Pp
.Nm
ports are named
.Pa vale[bdg:][port]
where
.Pa vale
is the prefix indicating a VALE switch rather than a standard interface,
.Pa bdg
indicates a specific switch (the colon is a separator),
and
.Pa port
indicates a port within the switch.
Bridge and port names are arbitrary strings, the only
constraint being that the full name must fit within 16
characters.
.Pp
See
.Xr netmap 4
for details on the API.
.Ss LIMITS
.Nm
currently supports up to 4 switches, 16 ports per switch, with
1024 buffers per port.
These hard limits will be
changed to sysctl variables in future releases.
.Sh SYSCTL VARIABLES
.Nm
uses the following sysctl variables to control operation:
.Bl -tag -width dev.netmap.verbose
.It dev.netmap.bridge
The maximum number of packets processed internally
in each iteration.
Defaults to 1024, use lower values to trade latency
with throughput.
.Pp
.It dev.netmap.verbose
Set to non-zero values to enable in-kernel diagnostics.
.El
.Sh EXAMPLES
Create one switch, with a traffic generator connected to one
port, and a netmap-enabled tcpdump instance on another port:
.Bd -literal -offset indent
tcpdump -ni vale-a:1 &
pkt-gen  -i vale-a:0 -f tx &
.Ed
.Pp
Create two switches,
each connected to two qemu machines on different ports.
.Bd -literal -offset indent
qemu -net nic -net netmap,ifname=vale-1:a ... &
qemu -net nic -net netmap,ifname=vale-1:b ... &
qemu -net nic -net netmap,ifname=vale-2:c ... &
qemu -net nic -net netmap,ifname=vale-2:d ... &
.Ed
.Sh SEE ALSO
.Xr netmap 4
.Pp
.Xr http://info.iet.unipi.it/~luigi/vale/
.Pp
Luigi Rizzo, Giuseppe Lettieri: VALE, a switched ethernet for virtual machines,
June 2012, http://info.iet.unipi.it/~luigi/vale/
.Sh AUTHORS
.An -nosplit
The
.Nm
switch was designed and implemented in 2012 by
.An Luigi Rizzo
and
.An Giuseppe Lettieri
at the Universita` di Pisa.
.Pp
.Nm
was funded by the European Commission within FP7 Projects
CHANGE (257422) and OPENLAB (287581).