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     vale — a very fast Virtual Local Ethernet using the netmap API


     device netmap


     vale is a feature of the 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.

     vale 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.


     vale dynamically creates switches and ports as clients connect to it using the netmap(4)

     vale ports are named vale[bdg:][port] where vale is the prefix indicating a VALE switch
     rather than a standard interface, bdg indicates a specific switch (the colon is a
     separator), and 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

     See netmap(4) for details on the API.

     vale 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.


     vale uses the following sysctl variables to control operation:

     dev.netmap.bridge   The maximum number of packets processed internally in each iteration.
                         Defaults to 1024, use lower values to trade latency with throughput.

     dev.netmap.verbose  Set to non-zero values to enable in-kernel diagnostics.


     Create one switch, with a traffic generator connected to one port, and a netmap-enabled
     tcpdump instance on another port:

           tcpdump -ni vale-a:1 &
           pkt-gen  -i vale-a:0 -f tx &

     Create two switches, each connected to two qemu machines on different ports.

           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 ... &



     Luigi Rizzo, Giuseppe Lettieri: VALE, a switched ethernet for virtual machines, June 2012,


     The vale switch was designed and implemented in 2012 by Luigi Rizzo and Giuseppe Lettieri at
     the Universita` di Pisa.

     vale was funded by the European Commission within FP7 Projects CHANGE (257422) and OPENLAB