CIS 120 Chapter 3

LDAP (Lightweight Directory Access Protocol)

A standard protocol for accessing network-based directories.

PAT (Port Address Translation)

A subset of NAT which assigns a separate TCP port to each session between a local host and an internet host.

NAT (Network Address Translation)

A technique designed to conserve the number of public IP addresses needed by a network.

TXT (text) record

A type of DNS data record that holds any type of free-form text. Used by SPF and DKIM.

AAAA (Address) record

A type of DNS data record that holds the name-to-address mapping for IPv6 addresses.

MX (Mail Exchanger) record

A type of DNS data record that identifies an email server and is used for email traffic.

SRV (Service) record

A type of DNS data record that identifies the hostname and port of a computer that hosts a specific network service besides email, such as FTP or SIP.

NS (Name server) record

A type of DNS data record that indicates the authoritative name server for a domain. Mostly used for delegating subdomains to other name servers.

PTR (Pointer) record

A type of DNS data record that is used for reverse lookups, which provide a host name when you know its IP address. Usually created by ISP, and stored in a specially formatted reverse lookup zone file, or reverse zone.

A (Address) record

A type of DNS data record that stores the name-to-address mapping for a host.

LDAPS (LDAP over SSL)

A type of LDAP that uses SSL to encrypt its communications.

MAC Address

A unique address embedded on every NIC on the globe and assumed to be unique to that NIC. Contains 2 parts, 48 bits long, and are written as six hex numbers separated by colons, like 00:60:8C:00:54:99

FQDN (Fully Qualified Domain Name)

A unique character-based name that is assigned to every host on a network (ex: www.mycompany.com).

SPF (Sender Policy Framework)

A validation system that helps fight spam by identifying the email servers allowed to send email on behalf of a domain.

Link local address

An IP address that can be used to communicate with nodes in the same link, and is similar to an autoconfigured APIPA address in IPv4.

Multicast address

An IP address that delivers packets to all nodes in the targeted, multicast group.

Anycast address

An IP address that identifies multiple destinations, with packets delivered to the closest destination.

Dynamic IP address

An IP address that is automatically assigned to a host by a DHCP server.

Public IP address

An IP address that is available for use on the Internet. Class A, B, and C licensed IP addresses are this type.

Private IP address

An IP address that is used on networks that don't directly connect to the Internet.

Global address

An IPv6 address that can be routed on the Internet. These addresses are similar to public IPv4 addresses. Most global addresses begin with the prefix 2000::/3, although other prefixes are being released.

IP address

An address assigned to nearly every interface, and can be used to find any computer in the world if the ________________ is public on the Internet. The first part identifies the network, and the last part identifies the host.

IPv6 address

An address that has 128 bits and is written as eight blocks of hex numbers. Ex: 2001:0DB8:0B80:0000:0000:00D3:9C5A:00CC

IPv4 address

An address that has 32 bits and is written as four decimal numbers called octets. Each octet, when written in binary, consists of exactly 8 bits.

DKIM (Domain Keys Identified Mail)

An authentication method that uses encryption to verify the domain name of an email's sender.

Classful addressing

An older method of managing IP address ranges. Divides IP addresses into classes A, B, C, D, and E based on the numerical range of IP addresses.

Forwarding DNS server

An optional server that receives queries from local clients but doesn't work to resolve the queries. Has its own DNS cache from previous queries, so it might already have the information a client needs. If not, it forwards the query to another server to resolve.

Link (local link)

Any LAN bounded by routers.

Subnet ID

Can be used to identify a subnet on a large corporate network.

Name servers

Computers that hold namespaces, organized in a hierarchical structure.

Socket

Consists of both a host's IP address and a process's TCP or UDP port, with a colon separating the two values.

Resolvers

DNS clients that request information from DNS name servers.

TTL (Time to live)

In an actual DNS zone file, each resource record beings with a ___ field that identifies how long the record should be saved in a cache or on a server. Administrators can change this.

Well-known ports

Port numbers that range from 0-1023 and assigned by IANA to widely used and well-known utilities and applications, such as Telnet, FTP, and HTTP.

Registered ports

Port numbers that range from 1024-49151 and can be used temporarily by processes for nonstandard assignments for increased security.

Unicast address

Specifies a single node on a network.

DMZ (demilitarized zone)

The area between the firewall for the external DNS and the firewall for the internal DNS.

Primary DNS server

The authoritative name server for the organization, which holds the authoritative DNS database for the organization's zones.

Authoritative server

The authority on computer names and their IP addresses for computers in their domains.

Secondary DNS server

The backup authoritative name server for the organization.

DNS zone

The domains that the organization is responsible for managing are collectively called a ________________.

Namespace

The entire collection of computer names and their associated IP addresses stored in databases on DNS name servers around the globe.

OUI (Organizationally Unique Identifier)

The first 24 bits (six hex characters) of a MAC address and identifies the NIC's manufacturer. Assigned by the IEEE (Institute of Electrical and Electronics Engineers)

Host name

The first part of a FQDN, which identifies the individual computer on the network (ex: www)

Default gateway

The gateway device that nodes on the network turn to first for access to the outside world.

Extension identifier (device ID)

The last 24 bits (six hex characters) of a MAC address and identifies the device itself.

Interface ID

The last 64 bits, or four blocks, of an IPv6 address that identifies the interface.

TLD (top-level domain)

The last part of an FQDN (ex: .com)

Domain name

The last two parts of a FQDN that matches the name of the organization's domain or network (ex: mycompany.com)

BIND (Berkeley Internet Name Domain)

The most popular DNS server software, which is free and open source (meaning it is publicly available for use and modification).

Host ID (node ID)

The network portion of an IP address.

IANA (Internet Assigned Numbers Authority)

The organization responsible for tracking the assignments of IP addresses, port numbers, and domain names.

Name resolution

The process of discovering the IP address of a host when its FQDN is known.

Address translation

The process of substituting a private IP address used by computers on a private network with the public IP address of a gateway device or router when these computers need access to other networks or the Internet.

Prefix discovery

The process where a computer sends an RS message to a router, and the router responds with an RA message, and the computer uses the information in the RA message.

Zone transfer

The process where a secondary DNS server makes a request to the primary DNS server to update its database.

Neighbors

Two or more nodes on the same link.

Dual stacked

When a network is configured to use both IPv4 and IPv6 protocols,it is a ____________ network.

CNAME (Canonical Name) record

A DNS record that holds alternative names for a host. These names can be used in place of the canonical name, which is the complete and properly formatted name, such as www.mycompany.com

ifconfig

A command only available on UNIX and Linux systems that is used to view and manage TCP/IP settings.

nslookup

A command that allows you to query the DNS database from any computer on the network and find the host name of a device by specifying its IP address, or vice versa. This is useful for verifying that a host is configured correctly or for troubleshooting DNS resolution problems.

dig

A command that is available on Linux and mac OS and provides more detailed domain information than nslookup. Used to query DNS name servers for information about host addresses and other DNS records. Newer than nslookup; uses more reliable sources of information.

ipconfig

A command that shows current TCP/IP addressing and domain name information on a Windows computer. Can also be used to change some of these settings.

ping (Packet Internet Groper)

A command used to verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. Starts by sending out a signal called an echo request to another computer, which is simply a request for a response. The other computer then responds to the request in the form of an echo reply.

Gateway

A computer, router, or other device that a host uses to access another network.

Firewall

A dedicated device or software on a computer that selectively filters or blocks traffic between networks.

DNAT (Destination NAT)

A form of NAT where hosts outside the network address a computer inside the network by a predefined public IP address. When a message sent to the public IP address reaches the router managing ____, the destination IP address is changed to the private IP address of the host inside the network. Changes the destination IP address of incoming messages and is often used by large organizations that provide services to the Internet.

SNAT (Static NAT)

A form of NAT where the gateway assigns the same public IP address to a host each time it makes a request to access the Internet. Used by small home networks with only a single public IP address provided by its ISP. Changes the source of outgoing messages and is used to reduce the number of public IP addresses needed by a network.

ICMP (Internet Control Message Protocol)

A lightweight protocol used to carry error messages and information about a network. Used by the ping command.

RA (Router Advertisement) Message

A message that responds to an RS message. Comes from the router with DHCP information.

RS (Router Solicitation) Message

A message when the computer asks if a router on the network can provide configuration information.

Tunneling

A method of transporting IPv6 packets through or over an IPv4 network. Also used for IPv6 transmission on the Internet.

Interface

A network connection made by a node on a network. A node's attachment to a link.

DHCP (Dynamic Host Configuration Protocol)

A network protocol to dynamically assign IP addresses to clients.

Port

A number used by the Transport layer to find an application or process. It identifies one application among several that might be running on a host.

Hex number

A number written in the base-16 number system, which uses the numerals 0-9, and A-F.

Binary number

A number written in the base-2 number system, which uses only the numerals 0 and 1.

Static IP address

A permanent IP address that is manually assigned to a computer

TFTP (Trivial File Transfer Protocol)

A protocol most commonly used by computers as they are booting up to request configuration files from another computer on the local network. Uses UDP.

SMB (Server Message Block)

A protocol that was first used by earlier Windows OSes for file-sharing on a network.

Recursive query

A query used by the DNS server that demands a resolution or the answer "It can't be found".

Iterative query

A query used by the DNS server that doesn't demand resolution.

Caching DNS server

A server that accesses public DNS data and caches the DNS information in collects. Receives DNS queries from local network clients and works to resolve them by contacting other DNS servers for information.

Root server

A server that holds information used to locate the TLD (top-level domain) servers (.com, .org, etc).

DNS server

A server that is responsible for tracking computer names and their IP addresses.

DNS (domain name system/service)

A service that was designed to associate computer names with IP addresses.

SIP (Session Initiation Protocol)

A signaling protocol that is used to make an initial connection between hosts but that doesn't participate in data transfer during the session.

H.323

A signaling protocol used to make a connection between hosts prior to communicating multimedia data. Largely replaced by SIP.

NTP (Network Time Protocol)

A simple protocol used to synchronize clocks on computers throughout a network. It can almost completely account for the variable delays across a network, even on the open Internet.

Private ports

Port numbers assigned by a network administrator that is different from the well-known port number for that service.

Subnet mask (netmask)

A 32-bit number that helps one computer find another. The 32 bits are used to indicate what portion of an IP address is the network portion.

Dynamic ports

Port numbers assigned by a client or server as the need arises.