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Service Location Protocol: Automatic Discovery of IP Network Services

Service Location Protocol: Automatic Discovery of IP Network Services. Erik Guttman, Sun Microsystems IEEE INTERNET COMPUTING, July-August, 1999 2005.10.17 Jongsoo Lee ( jslee@mmlab.snu.ac.kr ). Content. Introduction How can I use …? Background Service Location Protocol Comparison

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Service Location Protocol: Automatic Discovery of IP Network Services

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  1. Service Location Protocol:Automatic Discovery of IP Network Services Erik Guttman, Sun Microsystems IEEE INTERNET COMPUTING, July-August, 1999 2005.10.17 Jongsoo Lee (jslee@mmlab.snu.ac.kr)

  2. Content • Introduction • How can I use …? • Background • Service Location Protocol • Comparison • Conclusion

  3. How can I use …? Printer NTP server They invite a guest for some project. A certain laboratory in SNU Printer IP is …… NTP server Is …… No news server. How can I use news? How can I sync time? How can I print? It’s uncomfortable!!!

  4. Background • Problems with Earlier Protocols • Discover services only by type • Notorious lack of scalability • Service Location Protocol (SVRLOG) WG • 1997 : Version 1 (RFC 2165) • 1999 : Version 2 (RFC 2608) • 2002 : Vendor Extensions (RFC 3224) • SUN, Novell, IBM, Apple, HP, …

  5. Content • Introduction • Service Location Protocol • Architecture • Operation • For Various-size Network • Additional Features • Comparison • Conclusion

  6. Architecture SrvRqst (m) UA SrvRqst (m) SAAdvert (u) DAAdvert (m) SrvReg (u) SrvAck (u) SA SA SrvRqst (u) SrvRply (u) UA DA UA SA SA DAAdvert (u) SrvRply (u) UA UA • Agents • User Agents (UA) : service discovery • Service Agents (SA) : service advertisement • Directory Agents (DA) : service info aggregation UA

  7. Operation • Service Advertisements • Service URL contains service’s location • Follow the service templates (registered with IANA) • Attributes, default values and interpretation • DA Discovery • Multicast Convergence Algorithm • Active / Passive discovery • DHCP • Service Templates, and search filters = LDAPv3

  8. Mandatory Service Request : 1 Service Reply : 2 Service Registration : 3 Service Acknowledge : 5 DA Advertisement : 8 SA Advertisement :11 Optional Service Deregistration : 4 Attribute Request : 6 Attribute Reply : 7 Service Type Request : 9 Service Type Reply : 10 Operation - messages SrvRqst : service-type, scope-list, predicate SrvRply : URL-list SrvReg : service-type, scope-list, attr-list Advertisements : URL, scope-list, attr-list

  9. For Various-size Network Scope = “guest” • Larger Network • More DA • Scope • A string used to group resources by location, network, or administrative category • DHCP→ static configuration → “DEFAULT” • Small Network • SLP can work without DA, DNS and DHCP guest administrator SA UA SA SA

  10. Additional Features • Security • Authentication of the source of information. • SrvReg of SA include a digital signature using public key • DA is also possible • Browsing • Service Type Request • Attribute Request • IPv6 • Designed to provide service in IPv6 network • But not yet been standardized

  11. Content • Introduction • Service Location Protocol • Comparison • Conclusion

  12. Comparison • DHCP Service Options • Can’t determine a current available server • DNS Resource Records • Can’t determine a current available server • Only by type, and not by service characteristics • Simple Multicast Discovery • Scalability • Jini • Similar with SLP, but only for Java application

  13. Content • Introduction • Service Location Protocol • Comparison • Conclusion

  14. Conclusion • IETF standard for service discovery and automatic configuration of clients. • SLP provide fully decentralized operation • From a small network to an enterprise network • Convenience & Easy administration

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