TCP/IP Networking Basics

TCP/IP Networking Basics

• TCP/IP is a set of protocols that operate at different layers, used for interoperability among different types of computers.
• It specifies four layers: Application, Transport, Internet, and Network Interface.

Internet Protocol (IP)

• IP is used at the Internet layer of TCP/IP to attach network addresses to packets.
• In IPv4, an IP address consists of 4 octets between 0 and 255, separated by dots.
• Every Internet domain has at least one IP address on the Internet.

ICMP (Internet Control Message Protocol)

• ICMP is used to transmit status and error messages between network stations.
• It is used for reporting errors and performing network diagnostics.
• Five types of errors are handled in ICMP: Destination Unreachable, Source Quench, Time Exceeded, Parameter Problems, and Redirection.

Destination Unreachable

• When a router cannot route a datagram, it sends a Destination Unreachable message back to the source host.

ARP (Address Resolution Protocol)

• ARP maps logical to physical addresses.
• A host or router sends an ARP query packet to get the physical address of the receiver.
• The response packet contains the recipient's IP and physical addresses.

RARP (Reverse Address Resolution Protocol)

• RARP is used when a host knows its physical address but needs to know its logical address.
• A RARP request is created and broadcast on the local network, and another machine responds with a RARP reply.

Transport Layer Protocols

• Two protocols operate at the Transport layer: UDP (User Datagram Protocol) and TCP (Transmission Control Protocol).

TCP

• TCP is a reliable, guaranteed-delivery protocol that creates a virtual connection between two TCPs to send data.
• It uses a three-step process to set up a connection: SYN, SYN-ACK, ACK (three-way handshake).
• TCP requires the source host to resend packets that are not acknowledged.

UDP

• UDP is a simple, connectionless protocol that provides low overhead data delivery.
• It does not provide guaranteed data delivery or flow control.
• There is no error control mechanism in UDP.

DHCP (Dynamic Host Configuration Protocol)

• DHCP is used to dynamically assign IP addresses and configuration information to clients on a network.
• A DHCP scope determines which IP addresses are allocated to clients and defines a set of IP addresses and associated configuration information.
• A scope must be defined and activated before DHCP clients can use the DHCP server for dynamic TCP/IP configuration.

DHCP Scope

• The IP addresses defined in a DHCP scope must be contiguous and are associated with a subnet mask.
• A scope can be created to encompass all the addresses you want to assign, and then exclude specific addresses or address ranges from the scope.

Available Address Pool

• Once a DHCP scope is defined and exclusion ranges are applied, the remaining addresses form an available address pool within the scope.
• Pooled addresses can then be dynamically assigned to DHCP clients on the network.

Superscope

• A DHCP superscope is an administrative grouping of scopes that is used to support multinets on a single network segment.
• Superscopes contain only a list of member scopes or child scopes that can be activated together.

DHCP Reservation

• DHCP reservations are used for DHCP-enabled hosts that need to have static IP addresses on a network.
• Reservations must be created within a scope and must not be excluded from the scope.
• An IP address is set aside, or reserved, for a specific network device that has the Media Access Control (MAC) address associated with that IP address.

DHCP Options

• DHCP options are additional client-configuration parameters that a DHCP server can assign when serving leases to DHCP clients.
• DHCP options can be assigned to all scopes, one specific scope, or to a specific machine reservation.
• There are four types of DHCP options in Windows Server 2008: Server options, Scope options, Class options, and Client options.

Backup and Restore the DHCP Database

• Windows Server 2008 DHCP servers support automatic and manual backups.
• Backing up the DHCP database provides fault tolerance in case of a failure and enables restoration from the backup copy if the hardware fails.