Basic information on Active Directory, DNS, DHCP, RAID

DNS:
A Domain Naming server is a hierarchical namespace structure designed to provide host to IP address name resolution and registration.

DNS ZONE TYPE
Forward lookup zone: resolves names to IP address.
Reverse lookup zone: resolves IP addresses to Host names.

AD INTEGRATED ZONE
AD–integrated DNS enables AD storage and replication of DNS zone databases. Windows 2000 & 2003 DNS servers which accommodates storing zone data in AD. When you configure a computer as a DNS server, zones are usually stored as text files on name servers — that is, all of the zones required by DNS are stored in a text file on the server computer. These text files must be synchronized among DNS name servers by using a system that requires a separate replication topology and schedule called a zone transfer However, if you use AD integrated DNS you configure a domain controller as a DNS name server, zone data is stored as an AD object and is replicated as part of domain replication.

STUB ZONE
A Stub zone is a read only copy of a zone that contains only those resources records necessary to identify the authoritative DNS servers for the actual zone. A stub zone is used to keep a parent zone aware of authoritative DNS servers for a delegated zone and thereby maintain DNS name resolution efficiently. A stub zone is conposed of (A), (NS), (SOA)

Types of DNS Records:
- A(Host): Represents a computer or device on the network. 'A'records are the most common and most used DNS records.
- PTR(Pointer): Used for finding the DNS name that corresponds to an IP address. The PTR is found only in the reverse lookup zone.
- NS(NameServer): The NS RRs facilitate delegation by identifying DNS servers for each zone. They appear in all forward and reverse look-up zones.
- SOA(Start Of Authority):The first record in any zone file is a SOA. the SOA identifies a primary DNS name server for the zone as the best source of information for the data within that zone and as an entity processing the updates for the zone.
- SRV(Service Record):indicates a network service offered by a host.
- CNAME(Alias):an alias is hostname that refers to another hostname.

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DHCP: Is a standard for simplifing management of host IP configuration.

SUPERSCOPE: Superscope is a administrative feature of DHCP server that you can create and manage through the DHCP console. Using a Superscope you can group multiple scopes as a single administrative entity.
DHCP Authorize: This procedure is usually only needed if you are running a DHCP server on a member server. In most cases, if you are installing a DHCP server on a computer also running as a domain controller, the server is automatically authorized the first time you add the server to the DHCP console.

SCOPE: DHCP scope is a poole of IP addresses which are offered to DHCP clients.

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FSMO ROLES IN ACTIVE DIRECTORY

• Schema Master: The schema master domain controller controls all updates and modifications to the schema. To update the schema of a forest, you must have access to the schema master. There can be only one schema master in the whole forest.
• Domain naming master: The domain naming master domain controller controls the addition or removal of domains in the forest. There can be only one domain naming master in the whole forest.
• Infrastructure Master: The infrastructure is responsible for updating references from objects in its domain to objects in other domains. At any one time, there can be only one domain controller acting as the infrastructure master in each domain.
• Relative ID (RID) Master: The RID master is responsible for processing RID pool requests from all domain controllers in a particular domain. At any one time, there can be only one domain controller acting as the RID master in the domain.
• PDC Emulator: The PDC emulator is a domain controller that advertises itself as the primary domain controller (PDC) to workstations, member servers, and domain controllers that are running earlier versions of Windows. For example, if the domain contains computers that are not running Microsoft Windows XP Professional or Microsoft Windows 2000 client software, or if it contains Microsoft Windows NT backup domain controllers, the PDC emulator master acts as a Windows NT PDC. It is also the Domain Master Browser, and it handles password discrepancies. At any one time, there can be only one domain controller acting as the PDC emulator master in each domain in the forest.

REPLICATION Replication is a process of sending update information for data that has changed in the directory to other domain controllers, as a Part of the AD planning an implementation process.
*2000/2003 uses MULTI-MASTER replication for the AD.
*Types of UPDATES: Add, Modify, ModifyDN, delete
*USN: Update sequence numbers
*GUID: Globally unique identifier

REPLICATION PARTITIONS:
Schema Partition: contains object and attribute definitions. In other words it contains a list of definitions that define what objects and attributes for those objects can exist in the AD.
Configuration partition: contains information about the physical structure of the AD, such as the sites and domains and where DC resides in the enterprise. It is replicated to all DC's in the tree or forest.
Domain partition: contains information about all AD objects that are specific to that domain, such as users, groups and other resources. All domain partition information is completely replicated to all domain controllers within the domain.

REPLICATION TOPOLOGY
KCC: Knowledge Consistency Checker
**KCC uses only RPC to communicate with the directory service.
Bridgehead server: A point where a connection leaves or enters a site.
BENIFITS
• Optimize replication for speed and bandwidth consumption between domain controllers.
• Locate the closest domain controller for client logon, services, and directory searches.
• Direct a Distributed File System (DFS) client to the server that is hosting the requested data within the site.
• Replicate the system volume (SYSVOL), a collection of folders in the file system that exists on each domain controller in a domain and is required for implementation of Group Policy
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What is RAID?
ANS: Redundant Array of Inexpensive disk is a way to increase capaxity, performance and reliablility.

RAID0: (Striping) Not really RAID as it has no fault tolerance, Data is striped across all disks, Excelent read/write performance.
RAID1: (Mirroring) Need at least 2 drives, tolerates single drive failure, often used for OS drive or boot volume.
RAID5: Requires at least 3 drives, data and parity striped across all disks, can tolerate failure of any one disk without losing data but performance does degrade.

TCP/IP MODEL
Application Layer
Transport Layer
Internet
Network Interface

OSI MODEL

Application Layer
Presentation layer
Session layer
Transport Layer
Network Layer
Data-link Layer
Physical layer