SPECIFICATION
RAT uses TCP to ship very large packets to remote hosts.

SYNOPSIS
RAT is a protocol uses TCP to send very large packets to remote hosts. The current implementation of RAT manages a single TCP connection between each host pair. Messages pushed to RAT are in turn pushed to TCP. Unlike TCP RAT preserves packet boundaries. One the receiving end RAT reconstructs the original packet from an arbitrary list of buffers handed to it by TCP. RAT should be able to accept packets as large as the message tool implementation supports.

Note that RAT is totally responsible for the management of the TCP connection. In the current implementation this connection is not opened until a message is pushed to RAT. In the future more than one TCP connections between any two hosts could be supported without affecting the protocols which use RAT.

Currently a compiled constant in RAT determines the TCP send and receive buffer sizes.

RAT will almost always perform worse than BLAST on packets that are small enough for BLAST to deliver.

RAT uses any message attribute attached to the outgoing message to communicate the fact that it is reliable to some higher level protocol (in this case CHAN).

REALM
RAT is in the ASYNC realm.

PARTICIPANTS
The interface to RAT is intended to look as much like IP, VNET, and BLAST as possible. RAT assumes that the first participant passed to it at open time contains the IP address of the remote host. RAT openEnable takes participant which is ignored. OpenEables are based upon the protocol ID of the higher level protocol.

CONTROL OPERATIONS
RAT passes all control operations to IP the second protocol configured.

CONFIGURATION
RAT is not freely composable. It must be configured as follows:

name=rat protocols=tcp, ip

RAT has been designed to work under VSIZE with either BLAST, VNET, or IP as the short message protocol.

RAT recognizes the following ROM options:

rat/xxx sourcePort N: Instantiation xxx of RAT will use port N as its TCP source port. If N is equal to zero TCP will chose a port at random.

rat/xxx destPort N: Instantiation xxx of RAT will use port N as its TCP destination port. Each instance of RAT must have its own destination port.

AUTHORS
David C. Schwartz and Sean W. O'Malley