[cifs-protocol] [REG:115041612643080 ] MS-ADTS 6.2 - Knowledge consistency checker
edgaro at microsoft.com
Tue Apr 21 16:08:04 MDT 2015
Let’s approach this with NC, etc., as documented in MS-ADTS Section 6.2 (which does have specific mentions to RODC when necessary).
Please find the following summary based on source code review.
For each NC, Windows-based KCC calculates a minimum-cost spanning tree, by creating connection objects for each edge in the spanning tree which is incident with the local site. The first step is to setup a “colored vertex” list, which contains information about all sites which host this NC, and the bridgeheads which are available at those sites.
If the local site color is white or number of colored vertices is less than two, KCC does not need to build spanning tree for that NC. Either the local site does not host this NC, or the spanning tree would not have any edge. In either case, we do not need to compute the topology. KCC moves to the next NC in the list.
Recall that vertex initialization sets the color to ‘white’. The colored vertices are sites which contain a writeable or partial replica of the NC specified by CrossRef. Sites which contain at least one writeable replica are considered 'red' vertices. Sites which contain at least one partial replica but no writeable replicas are considered 'black' vertices. All other sites are considered 'white' vertices as marked during initialization, and are not colored.
Please take a look at the following references, including the non-MS-ADTS ones, they may be useful.
MS-ADTS 6.2.2 Overview
. . .
To simplify the task descriptions, the following concepts are used:
• An NC replica that "is present" on a DC. Given NC replica r of NC n and a DC with nTDSDSA object o, r "is present" on the DC if both of the following conditions is true:
o o!hasMasterNCs contains n or o!msDS-hasFullReplicaNCs contains n or o!hasPartialReplicaNCs contains n.
o One of the following two conditions is true:
o!msDS-HasInstantiatedNCs contains no value v where the dsname portion of v = n. (In this case n is in the process of being instantiated.)
o!msDS-HasInstantiatedNCs contains a value v, where the dsname part of v = n, and the binary part of v (DWORD in big-endian byte order) is an integer such that the IT_NC_GOING bit is clear. (In this case n is instantiated, and is not in the process of being uninstantiated.)
• An NC replica that "should be present" on a DC. Given NC replica r of NC n and a DC with nTDSDSA object o, r "should be present" on the DC if r is one of the following:
o A writable replica of the config NC, the schema NC, or the DC's default NC on a writable DC.
o A full read-only replica of the config NC, the schema NC, or the DC's default NC on an RODC.
o A writable replica of an application NC for which there exists a crossRef object cr such that cr!nCName = n and cr!msDS-NC-Replica-Locations contains a reference to o.
o A full read-only replica of an application NC for which there exists a crossRef object cr such that cr!nCName = n and cr.ms-DS-NC-RO-Replica-Locations contains a reference to o.
o If the DC is a GC server (that is, if bit NTDSDSA_OPT_IS_GC is set in o!options), a partial replica of a domain NC n such that n ≠ the DC's default NC, and there exists a crossRef object cr such that cr!nCName = n.
• An nTDSConnection object "implies" a tuple in the repsFrom abstract attribute of an NC replica (and a corresponding edge in an NC replica graph). An nTDSConnection object cn implies a tuple in r!repsFrom for NC replica r of NC n on the DC with nTDSDSA object t, if each of the following is true:
o cn is a child of t.
o cn!fromServer references an nTDSDSA object s.
o An NC replica of n "is present" on s.
o r "should be present" on t.
o The NC replica on s is a full replica or r is a partial replica.
o n is not a domain NC, or r is a partial replica, or cn!transportType has no value, or cn!transportType has an RDN of CN=IP.
Review Bridgehead Server Load-Balancing Improvements with Windows Server 2008 RODCs
Active Directory Replication Concepts
RODC Frequently Asked Questions
From: Edgar Olougouna
Sent: Thursday, April 16, 2015 10:23 AM
To: Garming Sam
Cc: cifs-protocol at samba.org; MSSolve Case Email
Subject: [REG:115041612643080 ] MS-ADTS 6.2 - Knowledge consistency checker
[case number in subject]
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Glad to hear from you. The case number 115041612643080 has been created for this inquiry. I will investigate and assist you on this.
From: Garming Sam [mailto:garming at catalyst.net.nz]
Sent: Wednesday, April 15, 2015 11:25 PM
To: Interoperability Documentation Help
Cc: cifs-protocol at samba.org
Subject: MS-ADTS 6.2 - Knowledge consistency checker
In attempting to implement the inter-site topology generation algorithm, it appears that cases around RODC are lacking clarity in the documentation.
For instance described in 184.108.40.206.3 - Site Graph Concepts, essentially Red describes sites with writable replicas, Black describes sites with only partial read-only and White with neither writable nor partial read-only replicas. But there is no mention of full read-only replicas.
The only assumption that could be made here is that they are white, however, there are two problems:
1. In 220.127.116.11.4.3 - Site Graph Construction under ColorVertices, Red describes sites with one or more DCs with full replicas - not writable.
This would make full read-only replica Red.
2. Being marked as White, during intersite topology generation, sites with only an RODC do not appear in the spanning-tree computation.
Therefore, they will never create any connections.
Being marked as Red however, there does not appear to be any restrictions in the graph construction on who may replicate from it (like a Black node for instance). Is there something here I am misunderstanding?
What color is a site containing only an RODC intended to be? And are there any additional undocumented special cases for RODC?
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