RFC 2968 (rfc2968) - Page 2 of 9
Mesh of Multiple DAG servers - Results from TISDAG
Alternative Format: Original Text Document
RFC 2968 Mesh of Multiple DAG servers October 2000 untouched, or a referral index server's contents could be aggregated into a new index object, generating referrals back to that server. The proposal is that the mesh should be constructed using index objects aggregated over participating services' servers. That is, referrals will be generated to other recognized services, not their individual participants. This can be done as a hierarchy or a level mesh one-layer deep, but the important reason for not simply passing forward index objects (unaggregated) is that individual services may support different ranges of access protocols, have particular security requirements, etc. Referrals should be directed to a CAP or CAPs -- either the standard ones used by the DAG system, or new ones established to support particular semantics of remote systems (e.g., other query types, etc). Within a given DAG system, referrals to these remote servers will look just like any other referral, although a particular SAP or SAPs may be established to provide query fulfillment (again, to enable translations between variations of service, to allow secure access if the relationship between the services is restricted, etc). In the following scenarios of mesh traversal, the assumption is that the primary service in discussion (Country A in Scenario 1, Country B in Scenario 2) is a DAG-based service. The scenarios are presented in the light of interoperating DAG services, but in most cases it would be equally applicable if the remote service was provided by some other service architecture. Again, the key element for establishing a mesh of any sort is the exchange of the CIP index object, not internal system architecture. 1.1.1 Scenario 1: Top Down Suppose 2 countries tie their services together. A user makes a query in Country A. A certain number of hits are made against the index objects of A's WDSPs. There is also a hit in the aggregate index of Country B. There are 3 possible cases under which this must be handled: Case 1: Country A and Country B are running services that are essentially the same -- in terms of protocols, queries, and schema that are supported. In this case, one referral should be generated per protocol supported by Country B's service. The referral can be passed back as far as the client, if its protocol supports referrals. Alternatively, the CAP may chain the referral through an appropriate SAP, in the usual fashion. In other words, the CAPs of Country B's service act as WDSPs to Country A's service. Daigle & Eklof Informational
