diff options
Diffstat (limited to 'man/man7/zmq_pgm.7')
| -rw-r--r-- | man/man7/zmq_pgm.7 | 98 |
1 files changed, 0 insertions, 98 deletions
diff --git a/man/man7/zmq_pgm.7 b/man/man7/zmq_pgm.7 deleted file mode 100644 index e1230ae..0000000 --- a/man/man7/zmq_pgm.7 +++ /dev/null @@ -1,98 +0,0 @@ -.TH zmq_pgm 7 "" "(c)2007-2010 iMatix Corporation" "0MQ User Manuals" -.SH NAME -0MQ PGM Transport \- reliable multicast transport -.SH SYNOPSIS - -PGM is a protocol for reliable multicast (RFC3208). 0MQ's PGM transport allows -you to deliver messages to multiple destinations sending the data over -the network once only. It makes sense to use PGM transport if the data, -delivered to each destination separately, would seriously load or even overload -the network. - -PGM sending is rate limited rather than controlled by receivers. Thus, to get -optimal performance you should set ZMQ_RATE and ZMQ_RECOVERY_IVL socket options -prior to using PGM transport. Also note that passing multicast packets via -loopback interface has negative effect on the overall performance of the system. -Thus, if not needed, you should turn multicast loopback off using ZMQ_MCAST_LOOP -socket option. - -PGM transport can be used only with ZMQ_PUB and ZMQ_SUB sockets. - -Caution: PGM protocol runs directly on top of IP protocol and thus needs to -open raw IP socket. On some operating systems this operation requires special -privileges. On Linux, for example, you would need to either run your application -as root or set adequate capabilities for your executable. Alternative approach -is to use UDP transport, -.IR zmq_udp(7) , -that stacks PGM on top of UDP and thus needs no special privileges. - -.SH CONNECTION STRING - -Connection string for PGM transport is "pgm://" followed by an IP address -of the NIC to use, semicolon, IP address of the multicast group, colon and -port number. IP address of the NIC can be either its numeric representation -or the name of the NIC as reported by operating system. IP address of the -multicast group should be specified in the numeric representation. For example: - -.nf - pgm://eth0;224.0.0.1:5555 - pgm://lo;230.0.0.0:6666 - pgm://192.168.0.111;224.0.0.1:5555 -.fi - -Note that NIC names are not standardised by POSIX. They tend to be rather -arbitrary and platform dependent. Say, "eth0" on Linux would correspond to "en0" -on OSX and "e1000g" on Solaris. On Windows platform, as there are no short NIC -names available, you have to use numeric IP addresses instead. - -.SH WIRE FORMAT - -Consecutive PGM packets are interpreted as a single continuous stream of data. -The data is then split into messages using the wire format described in -.IR zmq_tcp(7) . -Thus, messages are not aligned with packet boundaries and each message can start -at an arbitrary position within the packet and span several packets. - -Given this wire format, it would be impossible for late joining consumers to -identify message boundaries. To solve this problem, each PGM packet payload -starts with 16-bit unsigned integer in network byte order which specifies the -offset of the first message in the packet. If there's no beginning of a message -in the packet (it's a packet transferring inner part of a larger message) -the value of the initial integer is 0xFFFF. - -Each packet thus looks like this: - -.nf -+-----------+------------+------------------+-------- -| IP header | PGM header | offset (16 bits) | data ..... -+-----------+------------+------------------+-------- -.fi - -Following example shows how messages are arranged in subsequent packets: - -.nf -+---------------+--------+-----------+-----------------------------+ -| PGM/IPheaders | 0x0000 | message 1 | message 2 (part 1) | -+---------------+--------+-----------+-----------------------------+ - -+---------------+--------+-----------------------------------------+ -| PGM/IPheaders | 0xFFFF | message 2 (part 2) | -+---------------+--------+-----------------------------------------+ - -+---------------+--------+--------------------------+-----------+ -| PGM/IPheaders | 0x0008 | message 2 (last 8 bytes) | message 3 | -+---------------+--------+--------------------------+-----------+ -.fi - -.SH "SEE ALSO" - -.BR zmq_udp (7) -.BR zmq_tcp (7) -.BR zmq_ipc (7) -.BR zmq_inproc (7) -.BR zmq_setsockopt (3) - -.SH AUTHOR -Martin Sustrik <sustrik at 250bpm dot com> - - |