What is the character limit on individual domain names and the limit on the fully qualified domain names Fqdns )?

Curious to the limits of Active Directory?  This shows the maximum specifications of active directory.

Maximum Number of Objects

Each domain controller in an Active Directory forest can create a little bit less than 2.15 billion objects during its lifetime.

Maximum Number of Security Identifiers

There is a limit of approximately 1 billion security identifiers (SIDs) over the life of a domain. This limit is due to the size of the global relative identifier (RID) pool of 30 bits that makes each SID (that is assigned to user, group, and computer accounts) in a domain unique. The actual limit is 230 or 1,073,741,823 RIDs.

Group Memberships for Security Principals

Security principals (that is, user, group, and computer accounts) can be members of a maximum of approximately 1,015 groups.

FQDN Length Limitations

Fully qualified domain names (FQDNs) in Active Directory cannot exceed 64 characters in total length, including hyphens and periods (.).

File Name Length Limitations

The file system that Windows operating systems uses limits file name lengths (including the path to the file name) to 260 characters.

Organizational Unit Name Length

The maximum length for the name of an organizational unit (OU) is 64 characters.

Maximum Number of Group Policy Objects Applied

There is a limit of 999 Group Policy objects (GPOs) that you can apply to a user account or computer account.

Trust Limitations

Trust limitations arise from the number of trusted domain objects (TDOs), the length of trust paths, and the ability of clients to discover available trusts. Limitations that apply include the following:

• Kerberos clients can traverse a maximum of 10 trust links to locate a requested resource in another domain. If the trust path between the domains exceeds this limit, the attempt to access the domain fails.
• When a client searches out a trust path, the search is limited to the trusts that are established directly with a domain and the trusts that are transitive within a forest.
• Previous testing has shown that the time to complete operations related to TDOs, such as authentication across domains, deteriorates noticeably if the Active Directory implementation in an organization contains more than 2,400 TDOs.

Maximum Number of Accounts per LDAP Transaction

When you write scripts or applications that perform Lightweight Directory Access Protocol (LDAP) transactions, the recommended limit is to perform no more than 5,000 operations per LDAP transaction.

Recommended Maximum Number of Users in a Group

For Windows 2000 Active Directory environments, the recommended maximum number of members in a group is 5,000. This recommendation is based on the number of concurrent atomic changes that can be committed in a single database transaction.

So far, testing in this area has yet to reveal any new recommended limits to the number of members in a group or any other linked multi-valued attribute. Production environments have been reported to exceed 4 million members, and Microsoft scalability testing reached 500 million members.

Recommended Maximum Number of Domains in a Forest

For Windows 2000 Server, the recommended maximum number of domains in a forest is 800. For Windows Server 2003, the recommended maximum number of domains when the forest functional level is set to Windows Server 2003 (also known as forest functional level 2) is 1,200.

Recommended Maximum Number of Domain Controllers in a Domain

Because the File Replication Service (FRS) is used to replicate SYSVOL in a Windows Server 2003 domain, we recommend a limit of 1,200 domain controllers per domain to ensure reliable recovery of SYSVOL.

Recommended Maximum Kerberos Settings

The maximum recommended size for a Kerberos ticket is 65,535 bytes.

Posted from: Fabricem blog’s (aka Iceman) : Active Directory Maximum Limits – Scalability

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Format of IP address

Format of a domain name

Each element of a domain name separated by [.] is called a “label.” The maximum length of each label is 63 characters, and a full domain name can have a maximum of 253 characters. Alphanumeric characters and hyphens can be used in labels, but a domain name must not commence or end with a hyphen. Further, uppercase and lowercase letters are treated as equivalent. The right-most label conveys the “top-level domain (TLD),” and the second label from the right represents the “second level domain.” A label to the left of the second level domain is called the “third level domain”, and there can be fourth, fifth, etc. level domains.

DNS (Domain Name System)

The DNS is the system to associate IP addresses, which are easily processed by computers, to domain names, which are comprehensible to people. It is the equivalent of the address book for the Internet. Conversion of an IP address into a domain name, or vice versa, using the DNS is called “name resolution.”

The DNS forms a hierarchical structure, looking like a tree upside down (tree structure), with the top part called the “root” ([“ “] in the figure) and the space extending down to lower hierarchies. In this root space (the root zone), there is a DNS server called the root server, which has information on the manager of each TLD. Beneath the root, TLDs such as .com and .jp are allocated, and DNS servers for managing each TLD are placed. This works in a similar way for the second level domain, the third level domain and so on. Multiple domain names with the same label cannot exist in a given domain, so uniqueness is ensured across the entire space.

gTLD (Generic Top Level Domain)

Some domain names can be registered by anyone from anywhere in the world with no particular limitation, while others have certain conditions for registration. For example, a specific industry may be defined to be eligible to register a name under a particular domain. Examples of the former are .com, .net, .org and so on, and the latter applies to .edu, .pro, .museum and so on. The number of gTLDs as of September 2013 was 22, then a large-scale request for gTLD proposals commenced in 2012. New gTLDs have been added since October 2013, and the number exceeded 570 as of April 2015. Further additions will continue to be made in the future, and it is expected that more than 1,300 gTLDs will be added in the end.

ccTLD (Country Code Top Level Domain)

A ccTLD is a TLD allocated to each country or territory based on a two- letter code stipulated in ISO-3166-1 alpha-2 of the International Organization for Standardization (ISO), and it is based on the country code (two letters) of ISO 3166-1. There are 299 ccTLDs (including Internationalized Domain Names (IDNs)) as of April 2015. Management policy of ccTLDs is determined at each TLD, so some ccTLDs will accept registrations from anywhere in the world, while the others limit registration to entities located in their country or territory such as .jp.

JP domain name

The ccTLD for Japan, .jp, consists of four types: Organizational Type JP Domain Name, Geographic Type JP Domain Name, General-use JP Domain Name, and Prefecture Type JP Domain Name.

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