MTP Packet Types

   type       modifier     description

   data(0)    data(0)      The packet is one that contains user
                           information. Only the process possessing a
                           transmit token is permitted to send data
                           unless specifically requested to retransmit
                           previously transmitted data. All packets of
                           type data are multicast to the entire web.

              eow(1)       A data packet with the eow (end of window)
                           modifier set indicates that the transmitter
                           intends to send no more packets in this
                           heartbeat either because it has sent as many
                           as permitted given the window parameter or
                           simply has no more data to send during the
                           current heartbeat. This is not client
                           information but rather a hint to be used by
                           transport providers to synchronize the
                           computation and transmission of naks.

              eom(2)       Data[eom] marks the end of the message to the
                           consumers, and the surrendering of the
                           transmit token to the master. And like a
                           data[eow] a data[eom] packet implies the end
                           of window.

   nak(1)     request(0)   A nak[request] packet is a consumer
                           requesting a retransmission of one or more
                           data packets. The data field contains an
                           ordered list of packet sequence numbers that
                           are being requested. Naks of any form are
                           always unicast.

              deny(1)      A nak[deny] message indicates that the
                           producer source of the nak[deny]) cannot
                           retransmit one or more of the packets
                           requested. The process receiving the
                           nak[deny] must report the failure to its
                           client.

   empty(2)   dally(0)     An empty[dally] packet is multicast to
                           maintain synchronization when no client data
                           is available.

              cancel(1)    If a producer finds itself in possession of a
                           transmit token and has no data to send, it
                           may cancel the token[request] by multicasting
                           an empty[cancel] message.

              hibernate(2) If the master possesses all of the web's
                           transmit tokens and all outstanding messages
                           have been accepted or rejected, the master
                           may transmit empty[hibernate] packets at a
                           rate significantly slower than indicated by
                           the web's value of heartbeat.

   join(3)    request(0)   A join[request] packet is sent by a process
                           wishing to join a web to the web's unknown
                           TSAP (see section 2.2.5).

              confirm(1)   The join[confirm] packet is the master's
                           confirmation of the destination's request to
                           join the web. It will be unicast by the
                           master (and only the master) to the station
                           that sent the join[request].

              deny(2)      A join[deny] packet indicates permission to
                           join the web was denied. It may only be
                           transmitted by the master and will be unicast
                           to the member that sent the join[request].

   quit(4)    request(0)   A quit[request] may be unicast to the master
                           by any member of the web at any time to
                           indicate the sending process wishes to
                           withdraw from the web. Any member may unicast
                           a quit to another member requesting that the
                           destination member quit the web due to
                           intolerable behavior.  The master may
                           multicast a quit[request] requiring that the
                           entire web disband. The request will be
                           multicast at regular heartbeat intervals
                           until there are no responses to retention
                           requests.

              confirm(1)   The quit[confirm] packet is the indication
                           that a quit[request] has been observed and
                           appropriate local action has been taken.
                           Quit[confirm] are always unicast.

   token(5)   request(0)   A token[request] is a producing member
                           requesting a transmit token from the master.
                           Such packets are unicast to the master.

              confirm(1)   The token[confirm] packet is sent by the
                           master to assign the transmit token to a
                           member that has requested it. token[confirm]
                           will be unicast to the member being granted
                           the token.

   isMember(6) request(0)  An isMember[request] is soliciting
                           verification that the target member is a
                           recognized member of the web. All forms of
                           the isMember packet are unicast to a specific
                           member.

              confirm(1)   IsMember[confirm] packets are positive
                           responses to isMember[requests].

              deny(2)      If the member receiving the isMember[request]
                           cannot confirm the target's membership in the
                           web, it responds with a isMember[deny].