Issue 12509: The specification does not state how to generate unique GUIDs                                                                                                                                           (dds-interop-rtf)
Source: PrismTech (Mr. Niels Kortstee, niels.kortstee@prismtech.com Niels.Kortstee@prismtech.com)
Nature: Uncategorized Issue
Severity: 
Summary: In RTPS each entity has a so-called GUID_t. It consists of a 12 Byte GuidPrefix_and a 4-Byte EntityId_t and must be globally unique. In heterogeneous systems (with multiple RTPS implementations), the specification provides no mechanism or guidance to ensure global uniqueness.

A solution would be to make the vendorId part of the GuidPrefix_t.

Resolution:
The first two bytes of the GUID_t prefix should be the vendor id.

Resolution: The first two bytes of the GUID_t prefix should be the vendor id.
Revised Text: Add the following paragraphs to section 9.3.1.5  (Mapping of the GUID) above the paragraph that starts with "The reserved constant GUID_UNKNOWN "
Section 8.2.4 states that all RTPS Entities with a DomainParticipant share the same guidPrefix. Furthermore section Section 8.2.4.2 states that implementors have freedom to choose the guidPrefix as long as each DomainParticipant within a DDS Domain has a unique guidPrefix. 
The PIM restrict this freedom. Implementations of the protocol must choose the guidPrefix in such way that the first two Bytes match the vendorId . This will ensure that the guidPrefix remains unique within a DDS Domain even if multiple implementations are used. In other words, the guidPrefix must be chosen such that:
guidPrefix[0] = vendorId[0]
guidPrefix[1] = vendorId[1]
The reserved values of the vendorId are listed in Appendix A.

Proposed Disposition: Resolved

Actions taken:
May 20, 2008: received issue
Discussion: 

End of Annotations:=====
MG Issue No:  12509R#12
Title:	The specification does not state how to generate unique GUIDs
Source:
PrismTech (Niels Kortstee, Niels.Kortstee@prismtech.com)
Summary:
In RTPS each entity has a so-called GUID_t. It consists of a 12 Byte GuidPrefix_and a 4-Byte EntityId_t and must be globally unique. In heterogeneous systems (with multiple RTPS implementations), the specification provides no mechanism or guidance to ensure global uniqueness.

A solution would be to make the vendorId part of the GuidPrefix_t.

Resolution:
The first two bytes of the GUID_t prefix should be the vendor id.
Revised Text:

Add the following paragraphs to section 9.3.1.5  above the paragraph that starts with .The reserved constant GUID_UNKNOWN .
Section 8.2.4 states that all RTPS Entities with a DomainParticipant share the same guidPrefix. Furthermore section Section 8.2.4.2 states that implementors have freedom to choose the guidPrefix as long as each DomainParticipant within a DDS Domain has a unique guidPrefix. 
The PIM restrict this freedom. Implementations of the protocol must choose the guidPrefix in such way that the first two Bytes match the vendorId . This will ensure that the guidPrefix remains unique within a DDS Domain even if multiple implementations are used. In other words, the guidPrefix must be chosen such that:
guidPrefix[0] = vendorId[0]
guidPrefix[1] = vendorId[1]
The reserved values of the vendorId are listed in Appendix A.

Disposition: