1. XMLP Layer Underlying Protocol Layer XMLP Application 1 Handler b XMLP Processor XMLP Processor XMLP Application 2 XMLP Application 3 XMLP Processor Handler a Handler d Handler c Handler g Handler f Handler e XMLP Block 1 XMLP Block 2XMLP Block 3 XMLP Block 4 XMLP Message Underlying Protocol intermediary e.g. HTTP proxy SMTP relay Host IHost IIHost IIIHost IV Host V XMLP Sender & Receiver XMLP Receiver XMLP Node acting as initial sender XMLP Node acting as intermediary XML Node acting as ultimate receiver XMLP Sender XMLP Message Path Underlying Protocol Message Path Handler h XMLP_UNITDATA … XMLP_INTERMEDIARY

2. Sending XMLP Application Handler(b) Sending XMLP Processor Receiving XMLP Processor Intermediary XMLP Application Receiving XMLP Application Intermediary XMLP Processor Handler(a) Handler(d) Handler(c) Handler(g) Handler(f) Handler(e) XMLP Layer Underlying Protocol Layers XMLP Block 1 XMLP Block 2 XMLP Block 3 XMLP Block 4 XMLP Message ‘Transport’ Intermediary eg. HTTP Proxy SMTP Message Router XMLP_DATA XMLP_UNITDATA … XMLP_INTERMEDIARY Node INode IINode IIINode IV Node V

3. Handler(b) Sending XMLP Processor Receiving XMLP Processor Intermediary XMLP Processor Handler(a) Handler(d) Handler(c) Handler(g) Handler(f) Handler(e) XMLP Layer Underlying Protocol Layers XMLP Block 1 XMLP Block 2 XMLP Block 3 XMLP Block 4 XMLP Message ‘Transport’ Intermediary eg. HTTP Proxy SMTP Message Router XMLP_DATA XMLP_UNITDATA Node INode IINode IIINode IV Node V XMLProtocol Initiator/Sender XML Protocol Responder/Receiver XML Protocol Intermediary XMLP_INTERMEDIARY

4. XMLP_Data.request Initiating XMLP Application Responding XMLP Application XMLP_Data.indication XMLP_Data.response XMLP_Data.confirm XML Protocol Layer, Underlying Protocols and Medium Time

5. Sending XMLP Application Receiving XMLP Application XMLP_UnitData.send XMLP_UnitData.receive XML Protocol Layer Intervening Protocols and Medium XMLP_UnitData.status Time

6. Intermediary XMLP Application XMLP_Intermediary.receive XMLP_Intermediary.forward XML Protocol Layer, Underlying Protocols and Medium Time

7. Initiating XMLP ApplicationIntermediary XMLP Application Responding XMLP Application 1 2 3 4 5 6 Layer Primitives Key 1.XMLP_Data.request 2.XMLP_Intermediary.receive 3.XMLP_Intermediary.forward 4.XMLP_Data.indication 5.XMLP_Data.response 6.XMLP_Data.confirm Time

8. Layer Primitives Key 1.XMLP_Data.request 2.XMLP_Intermediary.receive 3.XMLP_Intermediary.forward 4.XMLP_Data.indication 5.XMLP_Data.response 6.XMLP_Data.confirm Numerical ordering indicates time sequence Initiating XMLP Application Intermediary XMLP Application Responding XMLP Application XMLP Layer 123456

9. Sending XMLP Application Intermediary XMLP Application Receiving XMLP Application 1 2 3 4 5 Layer Primitives Key 1.XMLP_UnitData.send 2.XMLP_Intermediary.receive 3.XMLP_Intermediary.forward 4.XMLP_UnitData.receive 5.XMLP_UnitData.status Time

10. Layer Primitives Key 1.XMLP_UnitData.send 2.XMLP_Intermediary.receive 3.XMLP_Intermediary.forward 4.XMLP_UnitData.receive 5.XMLP_UnitData.status (any time after 1) Numerical ordering indicates time sequence Sending XMLP Application Intermediary XMLP Application Receiving XMLP Application XMLP Layer 12345

11. XMLP_UnitData.receive XMLP_Intermediary.receive Or XMLP_UnitData.status XMLP_UnitData.send Or XMLP_Intermediary.forward Initiating, Responding, Sending, Receiving or Intermediary XML Protocol Application XML Protocol Handler XML Protocol Handler XML Protocol Handler … XMLP Layer

12. ab d c f e g Host I Host III Host V Host numbering from figure 2.1 h

13. XMLP Processor Underlying Protocol B Underlying Protocol A Underlying Protocol C Underlying Protocol D Protocol B Binding Protocol A Binding Protocol C Binding Protocol D Binding e.g. TCPe.g. SMTPe.g. HTTPe.g. BEEP XMLP_UNITDATA, XMLP_DATA XMLP_INTERMEDIARY Other MEP operations (TBD later) XMLP Application XMLP Hander(s) Binding Primitives OP MSG XMLP Layer