1. © 2000, D. Crocker, Brandenburg Consulting1 An Application Protocol Framework and a Model Application: Framing, Reporting, and Multiplexing Dave Crocker Brandenburg Consulting

2. © 2000, D. Crocker, Brandenburg Consulting2 Review of MRose slides  Framing 4Octet-stuffing (SMTP) 4Octet-counting (HTTP) 4Connection-blasting (FTP)  Multiplexing 4Parallelism 4Flow control 4Segmentation  Reporting 1st dig success or failure, permanent or transient 2nd dig system component making the report 3rd dig specific diagnostic Amusingly, this works well for everything except SMTP (ask Dave Crocker)

3. © 2000, D. Crocker, Brandenburg Consulting3 The decisons

4. © 2000, D. Crocker, Brandenburg Consulting4 Framing Header "REQ" SP more SP serial SP seqno SP size SP channel CR LF "RSP" SP more SP serial SP seqno SP size SP status [SP diagnostic] CR LF Payload MIME (Default = text/xml, 8bit) Trailer “END" CR LF Frame Report Status = Success (“+”) / Fail (“-”) Diagnostic - *ascii-text Semantics See “Channels” slide

5. © 2000, D. Crocker, Brandenburg Consulting5 Payload reporting In the RSP Payload 421 service not available 450 requested action not taken 451 requested action aborted 454 temporary authentication failure 500 general syntax error 501 syntax error in parameters 504 parameter not implemented 530 authentication required 534 authentication mechanism insufficient 535 authentication failure 537 action not authorized for user 538 authentication mechanism requires encryption 550 requested action not taken 553 parameter invalid 554 transaction failed

6. © 2000, D. Crocker, Brandenburg Consulting6 Mux: Channels  Frames exchanged in context of "channel" 4Associated "profile" defines syntax, semantics 4"Profile Registration" template defines how profile identified (using an URI) 4Channel 0 used for channel management  Examples 4Channel that negotiates transport security 4REQ. 1 0 94 0 END

7. © 2000, D. Crocker, Brandenburg Consulting7 Mux: Parallelism  Each channel processes requests serially  No constraints on the processing order between different channels.

8. © 2000, D. Crocker, Brandenburg Consulting8 Mux: Flow control  Replicate mechanism used by TCP 4Sequence numbers seqno 4Sliding window "SEQ" SP channel SP ackno SP window CR LF  Go home...

9. © 2000, D. Crocker, Brandenburg Consulting9 Mux: Segmentation More ="." / "*” Intermediate ("*") At least one other frame follows for the message Complete (".") this frame completes the data for the message