18.104.22.168.1 Sending a PDU
When an implementation of a higher-level protocol calls to an implementation of this protocol to send a PDU to the client, the implementation of this protocol MUST send the PDU on the default OUT channel to the outbound proxy, subject to flow control requirements as specified in section 22.214.171.124.1.
If the implementation of this protocol encounters an error while sending the data, it MUST take the following actions:
Indicate to the higher layer, in an implementation-specific way, that the operation failed.
Treat the connection as closed.
If the channel lifetime sent protocol variable for the default OUT channel approaches the channel lifetime as specified later in this paragraph, the implementation of this protocol MUST initiate channel recycling as defined in this section. An implementation MAY define when the number of bytes sent is approaching the channel lifetime in an implementation-specific way. However, it SHOULD define it in such a way as to open the successor OUT channel early enough so that it is fully opened before the predecessor channel has channel lifetime, and yet use as much of the predecessor channel as it can.<51>