Erik Guttman, Sun Microsystems IEEE INTERNET COMPUTING, July-August, Jongsoo Lee Service Location Protocol: Automatic Discovery of IP Network Services

2/14 Content Introduction How can I use …? Background Service Location Protocol Comparison Conclusion

3/14 How can I use …? A certain laboratory in SNU Printer NTP server How can I print? Printer IP is …… How can I sync time? NTP server Is …… How can I use news? No news server. They invite a guest for some project. It’s uncomfortable!!!

4/14 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, …

5/14 Content Introduction Service Location Protocol Architecture Operation For Various-size Network Additional Features Comparison Conclusion

6/14 Architecture Agents User Agents (UA) : service discovery Service Agents (SA) : service advertisement Directory Agents (DA) : service info aggregation SA UA DA SA UA SA SrvRqst (m) SrvRply (u) UA DAAdvert (m) SrvRqst (m) DAAdvert (u) SAAdvert (u) SrvRqst (u) SrvReg (u)SrvAck (u) SrvRply (u)

7/14 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

8/14 Operation - messages 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 SrvRqst : service-type, scope-list, predicate SrvRply : URL-list SrvReg : service-type, scope-list, attr-list Advertisements : URL, scope-list, attr-list

9/14 For Various-size Network 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 UA SA guest administrator Scope = “guest”

10/14 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

11/14 Content Introduction Service Location Protocol Comparison Conclusion

12/14 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

13/14 Content Introduction Service Location Protocol Comparison Conclusion

14/14 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