Client Interactions

INTROActive Directory Client Interactions

Central Database

LDAP – Lightweight Directory Access Protocol database query language, similar to SQL TCP/UDP 389, SSL TCP 636 Global Catalog (GC) – TCP/UDP 3268, SSL TCP 3269 D/COM Dynamic TCP – Replication

Kerberos UDP/TCP 88

Windows NT 4.0 SAM SMB/CIFS TCP 445 (or NetBIOS)

password resets, SAM queries SMB/DCOM Dynamic TCP

NTLM pass-through Kerberos PAC validation

Design Considerations

Distributed system DCs disconnected for very long times

several months Multimaster replication

with some FSMO roles

Design Considerations

Example: Caribean cruises, DC/IS/Exchange on board with tens of workstations and users, some staff hired during journey. No or bad satelite connectivity only. DCs synced after ship is berthed at main office.

Challenge: Must work independently for long time periods. Different independent cruise-liners/DCs can accomodate changes to user accounts, email addresses, Exchange settings. Cannot afford lost of any one.

Database

Microsoft JET engine JET Blue common with Microsoft Exchange used by DHCP, WINS, COM+, WMI, CA,

CS, RDS Broker %WINDIR%\NTDS\NTDS.DIT

ESENTUTL Opened by LSASS.EXE

Installed servicesLSASS

Security Accounts Manager

TCP 445SMB + Named

Pipes

Kerberos Key Distribution Center

UDP, TCP 88Kerberos

Active Directory Domain Services

UDP, TCP 389, ...LDAP

NTDS.DIT

D/COM Dynamic TCP

Network Interactions(DC Location)

Any DC2000+

Client2000+

LDAPUDP

SRV: Any DC List

Get My Site

DNSDNS

SRV: My Side DC

My Site DC

2000+

Network Interactions(2008/Vista+ DC Location)

Any DC2008+

ClientVista+

LDAPUDP

SRV: Any DC List

Get My Site

DNSDNS

SRV: My Site DC

Next Closest Site

Close Site DC2000+ My Site

DC2000+

SRV: Close Site

Network Interactions(Join Domain)

DC2000+

Client2000+

KerberosSMB

TGT: User

SAM Interface

TGT: CIFS

Network Interactions(Local Logon)

DC2000+

Client2000+

KerberosLDAPSMB

TGT: User

GPO List

GPO Download

TGS: LDAP, CIFS

Network Interactions (Kerberos Network Logon)

DC2000+

Client2000+

Kerberos

Server2000+

App Traffic

DC2000+

SMBD/COMTGT: User

In-bandTGS: Server

Occasional PAC

Validation

TGS: Server

D/COM Dynamic TCP

Network Interactions(NTLM Network Logon)

DC2000+

Client2000+

Server2000+

App Traffic

DC2000+

SMBD/COM

In-bandNTLM

Pass-through NTLM

D/COM Dynamic TCP

Network Interactions (Basic/RDP Logon)

DC2000+

Client2000+

Server2000+

App Traffic

DC2000+

In-bandclear text

KerberosTGT: User

ATTRIBUTE NOTESActive Directory Replication

Attribute Types

string, integer, datetime, boolean, binary DN reference multivalue

up to 5000 items linked multivalue

unlimited, requires 2003 Forest Level backlink

memberOf computed

primaryGroupToken, tokenGroups, lastLogonTimestamp write/only attributes

unicodePwd

Group membershipSales

CN=Kamil,OU=London,DC=...

CN=Judith,OU=Paris,DC=...

CN=Victor,OU=London,DC=...

CN=Stan,OU=London,DC=...

member

member

member

member

JudithCN=Sales,OU=Groups,DC

=...CN=IS

Access,OU=Groups,DC=...

memberOf

memberOf

Link

Backlink

(Not)replicated attributes Not replicated

logonCount badPasswordCount badPasswordTime lastLogon lastLogoff

Replicated pwdLastSet lockoutTime lastLogonTimestamp (since 2003)

Logon timestamps (2003 DFL)

Client

DC

DC

DC

lastLogon 11:38

lastLogon 9:00

lastLogon -

lastLogonTimestamp

11:00

lastLogonTimestamp

11:00

lastLogonTimestamp

11:00

lastLogonTimestamp

Requires 2003 domain level Updated only once per 14-random(5)

days DC=idtt,DC=local msDS-LogonTimeSyncInterval 1+ – minimum without randomization 5+ – randomization starts 14 – the default ...

Password changes

Password ChangeImmediate

Replication password

hash

hash

hash

Normal replication

Normal replication

DC

PDC

Client

Password changes

Client

DC

DC

DC

PDC

pwdLastSet

pwdLastSet pwdLastSet

pwdLastSet

Authentication failures

DC

PDC

pwd1

DC

pwd1

pwd1

Client


DC

PDC

pwd1

DC

pwd2

pwd2

Client

pwd2


Client

PDC

pwd2

DC

pwd2

pwd2

DC

pwd1


ClientDC

DC

badPasswordCount 3

badPasswordCount 2

PDC

badPasswordCount 7

lockoutTime

DC

badPasswordCount 2

DC LOCATIONActive Directory Client Interactions

Client Applications

Kerberos and NTLM authentication Secure Channel

password changes, NTLM pass-through, Kerberos PAC validation

Group Policy client DFS client Certificate Autoenrollment client

Client Applications

NPS (IAS), RRAS, TMG (ISA), RD Gateway (TS Gateway) group membership, Dial-In tab

RD Host (Terminal Server) Remote Control tab etc., Licensing servers

DHCP Server authorization

IIS account and group membership for SSL certificate

authentication WDS

computer MAC addresses or GUIDs

Connection Properties

Bandwidth (Mbps) forget about this

Latency (ms) round-trip-time (RTT) SMB, D/COM, SQL

Packet Loss (per sec., per Mb) packet loss rate (PLR) VPN such as PPTP, SSTP, IP-HTTPS

Timeouts

DNS primary DNS = 1 sec. secondary DNSs = 2 sec. ... 1 2 2 4 8 ...

ARP ... 600 ms 1000 ms

LDAP UDP Site Location 600 ms

TCP SYN = 21 sec. (3x retransmission) PSH/ACK = 93 sec. (5x retransmission) ... 3 6 12 24 48 ...

Basic DC location

Know the DNS name of the domain Query general DNS DC SRV records

_ldap._tcp.dc._msdcs.idtt.local Ping DC

Windows 2003- LDAP UDP (ping) DC

to get the client’s site/close site

DNS Domain Location

Makes use of DNS round robin Site unaware lookup

NSLOOKUP SET Q=SRV _ldap._tcp.dc._msdcs.idtt.local

Site specific lookup NSLOOKUP

SET Q=SRV _ldap._tcp.Paris._sites.dc._msdcs.idtt.local

London 10.10.x.x

Site Example – Single Site

DC1

DC2

DC3

Client

DC4

DC5

Paris10.20.x.x London 10.10.x.x

Site Example – Multihomed DC (DNS Bitmask Ordering)

DC1

DC2

DC3

Client

DC4

DC5

Berlin10.50.x.x

Paris10.20.x.xRoma

10.30.x.x

London10.10.x.x

Site Awareness

DC1

DC2

DC3

DC4

DC5

DC6

Client

where I am?Anonymous

LDAP UDP

General Operation

Use DNS to find generic DC list Ping selected DC

Windows 2003- Anonymous LDAP (UDP) to determine

site DC defines site from the request source IP

address (NAT?) Use DNS to find close DC in site Ping or LDAP UDP to determine

availability

DC Locator

NetLogon Service nltest /sc_query:idtt

no network access nltest /sc_verify:idtt

tries to authenticate with the DC nltest /sc_reset:idtt

always performs new DNS lookup nltest /dsgetsite

anonymous query against selected DC

DFS Client (MUP)

Multiple UNC provider (MUP) driver Determines its own DFS server

referrals obtains the list of DFS root servers from

AD using the default DC from Netlogon SYSVOL may be accessed from a

different DC DFSUTIL /PKTINFO

Windows Server 2003/Windows XP DFSUTIL CACHE REFERRAL

Windows Server 2008/Windows Vista

Paris10.20.x.x

Cyprus10.40.x.x

Roma10.30.x.x

London10.10.x.x

Site Example – Empty Site

DC1

DC2

DC3

DC4

DC5

DC6

DC7

Berlin10.50.x.x

Client

DC4

DC5

Automatic Site Coverage

Each DC registers itself for its neighboring empty sites

HKLM\System\CurrentControlSet\Services\Netlogon AutoSiteCoverage = DWORD = 1/0

GPO: Sites Covered by the DC Locator DNS SRV Records

MISPLACED OR CONFUSED CLIENTS

Active Directory Troubleshooting

Paris10.20.x.x

Cyprus10.40.x.x

Roma10.30.x.x

London10.10.x.x

Site Example – Out of Site

DC1

DC2

DC3

DC4

DC5

DC6

DC7

Berlin10.50.x.x

Client

10.100.0.7

Out-of-site clients

Limiting generic DC list

Limit creation of generic DC DNS records

GPO: Computer Configuration – Administrative Templates – System – Netlogon – DC Locator DNS Records DC Locator DNS Records not Registered Ldap, Kdc

DC Stickiness

When one close selected, client sticks to it even when moved into a different site must reset secure channel

Force rediscovery interval GPO Vista+ hotfix for Windows XP also registry value

ForceRediscoveryInterval

Paris10.20.x.x

Cyprus10.40.x.x

Roma10.30.x.x

London10.10.x.x

Site Example – Moving Client

DC1

DC2

DC3

DC4

DC5

DC6

DC7

Berlin10.50.x.x

Client

DC4

DC5

previously in Paris

CLIENT FAILOVERActive Directory Troubleshooting

Berlin10.50.x.x

Paris10.20.x.x

Cyprus10.40.x.x

Roma10.30.x.x

London10.10.x.x

Site Example – Failed DC

DC1

DC2

DC3

DC4

DC5

DC6

DC7 Clien

t

Non-close Site DC

Close site client’s site next closest site if enabled

If there is not DC available in the close site, rediscovery every 15 minutes HKLM\System\CurrentControlSet\

Services\Netlogon\Parameters CloseSiteTimeout = REG_DWORD = x

seconds

Paris10.20.x.x

Cyprus10.40.x.x

Roma10.30.x.x

London10.10.x.x

Site Example – Close Site

DC1

DC2

DC3

DC4

DC5

DC6

DC7

Berlin10.50.x.x

Client

Try Next Closest Site

First get any DC name from DNS Second query the DC for clients site

name returns the clients site plus the closest site (determined by the

DC) Then query DNS for DCs in its current

site and then tries to use the DCs If none responds, the client queries

DNS for its next closest site and tries to use the found DCs

Try Next Closest Site

Does not consider RODC sites by default Can be change in registry NextClosestSiteFilter

Windows 2003- cannot return the next closest site information problem if the hit “any DC” is Windows

2003- it is then going to be used regardless of

its site

Client Rules Recap

Windows 2003- In current site In any site

Windows Vista+ with Next closest site In current site In the closest site In any site

If the client is out of any site, find any dc consider creating subnets for VPNs etc.

SITE DESIGNActive Directory Client Interactions

Site Link Design

Site Link Design (Better?)

London

Olomouc

Roma

Cyprus

Paris

Berlin

Site Link Design (Worse?)

Olomouc

Roma

Cyprus

Paris

Berlin

London

DNS INTEGRATIONActive Directory Client Interactions

DNS Integration

Clients find DCs by domain/site name DCs find replication partners

according to their GUID Netlogon de/registers locator records DNS stores its data in

domain partition DomainDnsZones application partition ForestDnsZones application partition

Netlogon de/registration

Netlogon registers its own records at startup and deregisters them at shutdown requires DNS registration enabled on at

least one network adapter %windir%\System32\Config\netlogon.dns

It does not touch others’ records Autosite coverage

turned on by default

AD Integrated Zones

Offer Secure Dynamic Update Timestamping

trimmed to whole hour Aging and scavenging

records deleted by default between 14-21 days of their age

DNS Application Partitions Domain partition

CN=MicrosoftDNS,CN=System,DC=... DomainDnsZones

replicated to all DNS Server which are also DCs for the domain

ForestDnsZones replicated to all DNS Server which are

also DCs for the forest

Secure Dynamic Update

Client side feature DHCP Client on Windows 2003- DNS Client on Windows Vista+

DNS Server must be on DC to authenticate clients with Kerberos

All Authenticated Users can create new records

When a record is created, only the creator/owner can modify/update it

Secure Dynamic Update

Updates done regularly by clients every hour by default

Default TTL is 20 minutes Disable DHCP dynamic updates

insecure!

Dynamic Update

Primary DNS

Secondary DNS

Secondary DNS

Secondary DNSClient DNS1

3

2

SOA

Update

Adjust A/PTR Record TTL

Dynamic Update and Replication

DNS

AD AD

DNS

0 sec.

15-21 sec.

0-3 min.

schedule

Dynamic Update and Replication

Dynamic DNS Update on RODC Each writable DC returns itself as a

primary DNS RODC returns either (random)

writable DC as the primary DNS

Dynamic DNS Update on RODC

DNS

AD RODC

R/ODNS

0 sec.

Client

SOA

Upd1

2

Dynamic DNS Update on RODC

DNS

AD RODC

R/ODNS

0 sec.0-3 min.

Client

replicateSingleObject

0 sec.

Time stamping/Aging

Record Created timestamp trimmed to whole hour

No-refresh period starts by default 7 days timestamp does not change if the record

does not change Refresh period follows

by default next 7 days timestamp gets updated at the first

update

Scavenging

Server wide configuration Should be done by only one DNS

Server as best practice By default ocurres only once per 7

days

DNS Aging and Scavenging per-zone setting implemented by all

DNS servers timestamp updates

only during the refresh interval

limits replication traffic

DNS Aging and Scavenging per-server setting should be done only

by one of the DNS servers

DNS Aging and Scavenging

DNS Best Practice

DC1

DNS

DC2

DNS

ADAD

DNS Waiting for AD

DNS Best-Practice Reasons

Faster boot time without errors and timeouts

Deregistration at shutdown is recorded in live DNS Server would have problems replicate if sent

into shutting-down DC

Client DNS balancing

Clients do not balance DNS servers queries/updates use the first one always if possible

DHCP server does not use round robin

Configuration must be done “manually” manual on servers more DHCP scopes for clients

Client DNS non-balancing

Always alternateDNS serverIP addresses

Client DNS non-balancing

DNS1

DNS2

Client1

DNS1

DNS2

Client2

DNS1

DNS2

Client3

DNS1

DNS2

DNS Client Settings

HKLM\System\CurrentControlSet\Services\Tcpip\Parameters

Timetouts DNSQueryTimeouts

Disjoint namespace on multihomed machines DisjointNameSpace PrioritizeRecordData

GPO – DNS Suffix appending on Vista+

DNS Server UDP Pool

After applying KB 953230, DNS Server reserves 2500 UDP ports

HKLM\System\CurrentControlSet\Services\DNS\Parameters SocketPoolSize = DWORD = 2500

DNSCMD /Config /SocketPoolSize 2500

DNS Cache Pollution

server: idtt.com authoritative DNS server

question: test.idtt.com, type A answer: no records authority answer:

idtt.com SOA idtt.com NS ns37.domaincontrol.com ns37.domaincontrol.com A

216.69.185.19

GENERAL BEST PRACTICEActive Directory Troubleshooting

General Best Practice

Create and assign subnets for any possible client IP

Limit the general (site unaware) DNS registration of DCs

Enable Try next closest site and Force rediscovery options

Enable DNS Aging and Scavenging Alter clients’ DNS settings to rotate

the DNS server addresses

Client Interactions

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