MTP, Multicast Transport Protocol

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: TCP/IP.
Protocol type:Transport layer protocol.
Multicast addresses:
IP protocol:92.
MIME subtype:
Working groups:

MAC header IP header MTP bridge protocol header MTP header Data :::

MTP bridge protocol header:

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Destination port Source port
Length Checksum

Destination port. 16 bits.
The port to which the packet is destined or sinked.

Source port. 16 bits.
The port from which the packet originates or is sourced.

Length. 16 bits, 8 to 65535.
The length in bytes of the bridged packet, including header and the MTP packet. The length does not include any padding bytes that were used to compute the checksum.

Checksum. 16 bits.
The 16 bit one's compliment of the one's compliment sum of the entire bridge protocol header and MTP packet, padded with a zero byte (if necessary) to make multiple 16 bit quanities. A computed checksum of all zeros should be changed to all ones. Use of the checksum field is optional. If the field is cleared to zero, the checksum is not used.

MTP header:

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Version Type Type modifier Subchannel
Source connection identifier
Destination connection identifier
Message acceptance :::
Window Retention
Data :::

Version. 8 bits.
MTP version number.

Type. 8 bits.
Message type.

3 Join.
4 Quit.
5 Token.

Type modifier. 8 bits.

Subchannel. 8 bits.

Source connection identifier. 32 bits.
Contains a transmitting system unique value assigned at the time the transport is created. This field is used in identifying the particular transport instantiation and is a component of the TSAP. Every packet transmitted by the transport must have this field set.

Destination connection identifier. 32 bits.
The identifier of the target transport. From the point of view of a process sending a packet, there are three types of destination connection identifiers. First, there is the unknown connection identifier (0x00000000). The unknown value is used only as the destination connection identifier in the join[request] packet.

Second, there is the multicast connection identifier gleaned from the join[confirm] message sent by the master. The multicast connection identifier is used in conjunction with the multicast NSAP to form the destination TSAP of all packets multicast to the entire web.

The last class of connection identifier is a unicast identifier and is used to form the destination TSAP when unicasting packets to individual members. Every member of the web has associated with it a unicast connection identifier that is used to form its own unicast TSAP.

Message acceptance. Variable length.

Heartbeat. 32 bits, unsigned milliseconds.
The value of heartbeat is shared by all members of the web. By definition at least one packet (either data, empty or quit from the master) will be multicast into the web within every heartbeat period.

Window. 16 bits, unsigned.
The allocation window indicates the maximum number of data packets that can be multicasted by a member in a single heartbeat. It is the sum of the retransmitted and new data packets.

Retention. 16 bits, unsigned.
The number of heartbeats for which a producer must retain transmitted client data and state for the purpose of retransmission.



[RFC 1301] Multicast Transport Protocol.

[RFC 1458] Requirements for Multicast Protocols.


Obsolete RFCs:

Description Glossary RFCs Publications Obsolete RFCs