wirefilter - Wire packet filter for Virtual Distributed Ethernet
wirefilter
[
-f rcfile] [
-l loss] [
-l
lostburst] [
-d delay] [
-D dup] [
-b bandwidth] [
-s interface_speed] [
-c
channel_bufsize] [
-n noise_factor] [
-m
mtu_size] [
-M mgmt socket] [
-v
vde_plug1:vde_plug2] [
--daemon] [--pidfile
pidfile_path] [--blink blink]
[--blinkid blink_identifier] [-N]
A
wirefilter is able to emulate delays and packet loss on virtual wires.
e.g.:
dpipe vde_plug /tmp/s1 = wirefilter -l 10 = vde_plug /tmp/s2
creates a wire between two vde_switches (with sockets /tmp/s1 and /tmp/s2
respectively). This cable looses 10% of the packets in each direction.
The same cable can be created using:
wirefilter -v /tmp/s1:/tmp/s2 -l 10
- -f rcfile
- use a startup configuration file. It is useful for complex
defitions such as those for the Markov mode (see below). The startup
configuration file has the same syntax of the management interface, in
other word it is a script of management commands executed before the first
packet is forwarded.
- -l loss
- percentage of loss as a floating point number. It is
possible to specify different loss percentage for the two channels: LR20.5
means 20.5% of packet flowing left to right are lost, RL10 means 10% from
right to left.
- -L lostburst
- when this is not zero, wirefilter uses the Gilbert model
for bursty errors. This is the mean length of lost packet bursts. (it is a
two state Markov chain: the probability to exit from the faulty state is
1/lostburst, the probability to enter the faulty state is
loss/(lostburst-(1-loss)). The loss rate converges to the value
loss.
- -d delay
- Extra delay (in milliseconds). This delay is added to the
real communication delay. Packets are temporarily stored and resent after
the delay. It is possible to specify different values for LR and RL like
in the previous option. When the delay is specified as two numbers with a
+ in between, the first is the standard delay and the second is a random
variation. 1000+500 means that the delay can be randomly chosen between
half second and 1.5 seconds. It is possible to add 'U' or 'N' at the end.
1000+500U means that the dealys are uniformly distributed, 1000+500N means
that the delays follow a Gaussian normal distribution (more than 98% of
the values are inside the limits).
- -D dup
- percentage of dup packet. It has the same syntax of -l. Do
not use dup factor 100% because it means that each packet is sent infinite
times.
- -b bandwidth
- Channel bandwidth in Bytes/sec. It has the same syntax of
-d. It is also possible to use suffixes K,M,G to abbreviate 2^10, 2^20,
2^30. 128K means 128KBytes/sec. 128+64K means 64i to 196KBytes/sec. Sender
is not prevented from sending packets, delivery is delayed to limit the
bandwidth to the desired value. (Like a bottleneck along the path) U and N
after the values (e.g. 128+64KN) set the statistic distribution to use
(uniform or normal).
- -s speed
- Interface speed in Bytes/sec. It has the same syntax of -b.
Input is blocked for the tramission time of the packet, thus the sender is
prevented from sending too fast.
- -c channel_bufsize
- Channel buffer size (in Bytes): maximum size of the packet
queue. Exceeding packets are discarded.
- -n noise factor
- Number of bits damaged/one megabyte.
- -m mtu size
- Packets longer than mtu_size are discarded.
- -N
- nofifo. with -N packets can be reordered.
- -M mgmt socket
- the unix socket where the parameters (loss percentage,
delay etc) can be checked and changed runtime. unixterm(1) can be used as
a remote terminal for wirefilter.
- -v vde_plug1:vde_plug2
- If this option is used, the two local vde_plugs (vde_plug1
and vde_plug2) will be connected each other instead of stdin/stdout, using
the libvdeplug libraries. This option activates an interactive management
session on console (stdin/stdout).
- --mgmtmode mode
- this option sets the access mode of the mgmt socket. The
command syntax is quite simple. help provides the list of commands.
It is possible to load a script file using the load management
command.
- --daemon
- wirefilter becomes a daemon
- --pidfile pathnamefP
- wirefilter saves its pid into the file.
- --blinkid name
- This option defines the id sent for each packet to the
blink server (see the --blink option below). The stardard identifier for a
wirefilter is the process pid.
- --blink socket
- wirefilter sends a log message to the specified
PF_UNIX/DATAGRAM socket for each packet sent. Each packet has the format:
id direction length. e.g:
6768 LR 44
6768 LR 44
6768 RL 100
6768 LR 100
6768 LR 44
wirefilter provides also a more complex set of parameters using a Markov chain
to emulate different states of the link and the tranistions between states.
Each state is represented by a node. Markov chain parameters can be set with
management commands or rc files only. In fact, due to the large number of
parameters the command line would have been unreadable.
- markov-numnodes n
- defines the number of different states. All the parameters
of the connection can be defined node by node. Nodes are numbered starting
from zero (to n-1). e.g.:
delay 100+10N[4]
loss 10[2]
these command define a delay of 90-110 ms (normal distribution) for the node
number 4 and a 10 loss for the node 2. It is possible to resize the Markov
chain at run-time. New nodes are unreachable and do not have any edge to
other states (i.e. each new node has a loopback edge to the node itself
with 100% probability). When reducing the number of nodes, the weight of
the edges towards deleted nodes is added to the loopback edge. When the
current node of the emulation is deleted, node 0 becomes the current node.
(The emulation always starts from node 0).
- markov-time ms
- time period (ms) for the markov chain computation. Each
ms microseconds a random number generator decides which is the next
state (default value=100ms).
- markov-name n,name
- assign a name to a node of the markov chain.
- markov-setnode n
- manually set the current node to the node n.
- setedge n1,n2,w
- define an edge between n1 and n2; w is
the weight (probability percentage) of the edge. The loopback edge (from a
node to itself) is always computed as 100% minus the sum of the weights of
outgoing edges.
- showedges [ n ]
- list the edges from node n (or from the current node
when the command has no parameters). Null weight edges are omitted.
- showcurrent
- show the current Markov state.
- showinfo [ n ]
- show status and information on state (node) n. If
the parameter is omitted it shows the status and information on the
current state.
- markov-debug [ n ]
- set the debug level for the current management connection.
In the actual implementation when n is greater than zero each change of
markov node causes the output of a debug trace. Debug tracing get disabled
when n is zero or the parameter is missing.
Virtual Distributed Ethernet is not related in any way with
www.vde.com
("Verband der Elektrotechnik, Elektronik und Informationstechnik"
i.e. the German "Association for Electrical, Electronic & Information
Technologies").
vde_switch(1),
vdeq(1).
dpipe(1).
unixterm(1).
VDE is a project by Renzo Davoli <
[email protected]>