RFC 2165 Service Location Protocol June 1997 4. Service Location General Message Format 14 4.1. Use of Transaction IDs (XIDs) . . . . . . . . . . . . . . 15 4.2. URL Entries . . . . . . . . . . . . . . . . . . . . . . . 16 4.3. Authentication Blocks . . . . . . . . . . . . . . . . . . 17 4.4. URL Entry Lifetime . . . . . . . . . . . . . . . . . . . 19 5. Service Request Message Format 19 5.1. Service Request Usage . . . . . . . . . . . . . . . . . . 22 5.2. Directory Agent Discovery Request . . . . . . . . . . . . 23 5.3. Explanation of Terms of Predicate Grammar . . . . . . . . 24 5.4. Service Request Predicate Grammar . . . . . . . . . . . . 26 5.5. String Matching for Requests . . . . . . . . . . . . . . 27 6. Service Reply Message Format 28 7. Service Type Request Message Format 29 8. Service Type Reply Message Format 31 9. Service Registration Message Format 32 10. Service Acknowledgement Message Format 35 11. Service Deregister Message Format 37 12. Attribute Request Message Format 38 13. Attribute Reply Message Format 40 14. Directory Agent Advertisement Message Format 42 15. Directory Agents 43 15.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 43 15.2. Finding Directory Agents . . . . . . . . . . . . . . . . 43 16. Scope Discovery and Use 45 16.1. Protected Scopes . . . . . . . . . . . . . . . . . . . . 46 17. Language and Character Encoding Issues 47 17.1. Character Encoding and String Issues . . . . . . . . . . 48 17.1.1. Substitution of Character Escape Sequences . . . 49 17.2. Language-Independent Strings . . . . . . . . . . . . . . 49 18. Service Location Transactions 50 18.1. Service Location Connections . . . . . . . . . . . . . . 50 18.2. No Synchronous Assumption . . . . . . . . . . . . . . . . 51 18.3. Idempotency . . . . . . . . . . . . . . . . . . . . . . . 51 19. Security Considerations 51 20. String Formats used with Service Location Messages 52 20.1. Previous Responders' Address Specification . . . . . . . 53 20.2. Formal Definition of the "service:" Scheme . . . . . . . 53 20.2.1. Service Type String . . . . . . . . . . . . . . . 54 20.3. Attribute Information . . . . . . . . . . . . . . . . . . 54 20.4. Address Specification in Service Location . . . . . . . . 55 20.5. Attribute Value encoding rules . . . . . . . . . . . . . 55 21. Protocol Requirements 56 21.1. User Agent Requirements . . . . . . . . . . . . . . . . . 56 21.2. Service Agent Requirements . . . . . . . . . . . . . . . 58 21.3. Directory Agent Requirements . . . . . . . . . . . . . . 59 22. Configurable Parameters and Default Values 61 22.1. Service Agent: Use Predefined Directory Agent(s) . . . . 62 22.2. Time Out Intervals . . . . . . . . . . . . . . . . . . . 63 Veizades, et. al. Standards Track