Networking Essentials - Chapter 5

IP address

A 32-bit dotted-decimal address used by IP to determine the network a host resides on and to identify hosts on the network at the Internetwork layer.

Dynamic DNS (DDNS)

A DNS client and server option that allows a DNS client computer to register its hostname and IP address with a DNS server automatically. See also Domain Name System (DNS).

IP address scope

A component of a DHCP server, it's a range of IP addresses the server leases to clients requesting an IP address.

reservation

A configuration option for an IP address scope that ties an IP address to a MAC address. When a client requests an IP address from the DHCP server, if the client's MAC address matches an address specified by a reservation, the reserved IP address is leased to the client instead of getting it from the scope. See also IP address scope.

exclusion

A configuration option that excludes specified IP addresses from the DHCP IP address scope. See also IP address scope.

Secure Shell (SSH)

A secure Application-layer protocol used to connect to a device across a network via a command-line interface; uses TCP port 22.

protocol

Rules and procedures for communication and behavior. Computers must use a common protocol and agree on the rules of communication.

segment

The unit of information used by TCP in the Transport layer. A segment is passed up to the Application layer as data and passed down to the Internetwork layer, where it becomes a packet.

datagram

The unit of information used by UDP in the Transport layer. A datagram is passed up to the Application layer as data and passed down to the Internetwork layer, where it becomes a packet.

Dynamic Host Configuration Protocol (DHCP)

An Application-layer protocol used to configure a host's IP address settings dynamically; it uses UDP ports 67 and 68.

Transmission Control Protocol (TCP)

A connection-oriented Transport-layer protocol designed for reliable transfer of information in complex internetworks.

Internet Protocol version 6 (IPv6)

A connectionless Internetwork-layer protocol that provides source and destination addressing and routing for the TCP/IP protocol suite. Uses 128-bit hexadecimal addresses and has built-in security and QoS features.

Internet Protocol version 4 (IPv4)

A connectionless Internetwork-layer protocol that provides source and destination addressing and routing for the TCP/IP protocol suite; uses 32-bit dotted decimal addresses.

User Datagram Protocol (UDP)

A connectionless Transport-layer protocol designed for efficient communication of generally small amounts of data.

DNS zone

A database of primarily hostname and IP address pairs that are related by membership in an Internet or a Windows domain.

checksum

A field in the Transport-layer and Internetwork-layer headers that protects data integrity by providing a means for a receiving device to ensure that data hasn't been altered.

port number

A field in the Transport-layer protocol header that specifies the source and destination Application-layer protocols that are used to request data (the source) and are the target of the request (the destination).

flow control

A mechanism network protocols use to prevent a destination device from becoming overwhelmed by data from a transmitting computer, resulting in dropped packets.

fully qualified domain name (FQDN)

A name that includes the hostname, subdomain names (if applicable), second-level domain name, and top-level domain name, separated by periods.

Internet Message Access Protocol version 4 (IMAP4)

An Application-layer protocol used by an e-mail client to download messages from an e-mail server; operates on TCP port 143. IMAP4 also provides fault-tolerance features. It downloads only message headers from the server initially, and then downloads the message body and attachments after the message is selected.

Automatic Private IP Addressing (APIPA)

A private range of IP addresses assigned to an APIPA-enabled computer automatically when an IP address is requested via DHCP but no DHCP server responds to the request. See also Dynamic Host Configuration Protocol (DHCP).

three-way handshake

A series of three packets used between a client and server to create a TCP connection. After the three-way handshake has been completed successfully, a connection is established between client and server applications, and data can be transferred.

protocol suite

A set of protocols working cooperatively to provide network communication. Protocols are "stacked" in layers, and each layer performs a unique function required for successful communication. Also called a "protocol stack."

ARP cache

A temporary storage location in an IP host's RAM that keeps recently learned IP address/MAC address pairs so that the ARP protocol isn't necessary for each packet sent to a host.

connectionless protocol

A type of network communication in which data is transferred without making a connection between communicating devices first, and the receiving station gives no acknowledgement that the data was received.

Server Message Block (SMB)

An Application-layer protocol that Windows file and printer services use to share resources between Windows computers; uses TCP port 445.

Domain Name System (DNS)

An Application-layer protocol that resolves computer and domain names to their IP addresses; uses UDP port 53.

Post Office Protocol version 3 (POP3)

An Application-layer protocol used by a client e-mail application to download messages from an e-mail server; uses TCP port 110.

Remote Desktop Protocol (RDP)

An Application-layer protocol used to access a Windows computer remotely with the Windows GUI; uses TCP port 3389.

Simple Network Management Protocol (SNMP)

An Application-layer protocol used to monitor and manage network devices and gather statistics about network traffic. It operates on UDP ports 161 and 162.

Simple Mail Transfer Protocol (SMTP)

An Application-layer protocol used to send e-mail over the Internet; uses TCP port 25.

File Transfer Protocol (FTP)

An Application-layer protocol used to transfer and manage files across a network; uses TCP ports 20 and 21.

Address Resolution Protocol (ARP)

An Internetwork-layer protocol used to resolve a host's IP address to its MAC address. ARP uses a broadcast frame containing the target host's IP address, and the host that's assigned the address responds with its MAC address.

Internet Control Message Protocol (ICMP)

An Internetwork-layer protocol used to send error, status, and control messages between systems or devices. It's an encapsulated IP protocol, meaning it's wrapped in an IP header.

Internet Protocol Security (IPsec)

An extension to IP working at the Internetwork layer that provides security by using authentication and encryption. It authenticates the identity of computers transmitting data with a password or some other form of credentials, and it encrypts data so that if packets are captured, the data will be unintelligible.

Telnet

An unsecure Application-layer protocol used to connect to a device across a network via a command-line interface; uses TCP port 23.

resolver cache

Storage for recently resolved DNS data on a DNS client; used so that clients don't have to perform DNS lookups if host were resolved recently.

resource records

The data contained in a DNS zone, such as host records, MX records, and NS records.

Transmission Control Protocol/Internet Protocol (TCP/IP)

The most common protocol suite, TCP/IP is the default protocol in contemporary OSs and the protocol of the Internet.