Networking 2
scope ID
A % sign and a number at the end of an IPv6 address that is used to identify the link the computer belongs to.
zone ID
A % sign and a number at the end of an IPv6 address that is used to identify the link the computer belongs to.
OUI (Organizationally Unique Identifier) aka block ID aka company-ID
A 24-bit character sequence assigned by IEEE that appears at the beginning of a network interface's physical address and identifies the NIC's manufacturer.
resolver
A DNS client that requests information from DNS name servers.
recursive query
A DNS query that demands a resolution or the response that the information can't be found.
iterative queries
A DNS query that does not demand a resolution, which means the server provides the information only if it already has that information available.
root server
A DNS server maintained by ICANN and IANA that is an authority on how to contact the top-level domains, such as those ending with .com, .edu, .net, .us, and so on. ICANN oversees the operation of 13 clusters of root servers around the world.
Port Address Translation (PAT)
A form of address translation that assigns a separate TCP port number to each ongoing conversation, or session, between a local host and an Internet host.
reverse DNS lookup
A function that finds the host name of a device whose IP address is known.
command-line interface (CLI)
A graphic-free user interface, such as the Command Prompt program in Windows, where technicians can enter commands more quickly and with more flexibility than in a GUI (graphical user interface) environment.
NetBT (NetBIOS over TCP/IP)
A protocol that runs in the Session and Transport layers of the OSI model and associates NetBIOS names with workstations. NetBIOS allows old applications designed for out-of-date NetBIOS networks to work on TCP/IP networks.
hosts file
A text file that associates TCP/IP host names with IP addresses. On a UNIX- or Linux-based computer, hosts is found in the /etc directory. On a Windows-based computer, it is found in the %systemroot%\system32\ drivers\etc folder.
4 to 6
A tunneling protocol that enables transmission of IPv4 packets over an IPv6 network.
ISATAP (Intra-Site Automatic Tunnel Addressing Protocol)
A tunneling protocol that enables transmission of IPv6 packets over IPv4 networks. This protocol works only on a single organization's intranet.
Teredo
A tunneling protocol, named after the Teredo worm, that enables transmission of IPv6 packets over IPv4 networks. IPv6 addresses intended to be used by this protocol begin with the prefix 2001::/32.
CNAME (Canonical Name) record
A type of DNS data record that holds alternative names for a host.
MX (Mail Exchanger) record
A type of DNS data record that identifies a mail server and that is used for email traffic.
PTR (Pointer) record
A type of DNS data record that is used for reverse lookups, to provide a host name when the IP address is known.
A (Address) record
A type of DNS data record that maps the IPv4 address of an Internet-connected device to its domain name.
AAAA (Address) record
A type of DNS data record that maps the IPv6 address of an Internet-connected device to its domain name.
device ID
A unique set of characters assigned to each NIC by its manufacturer. In the traditional, 48-bit physical addressing scheme, the extension identifier is 24 bits long. In EUI-64, the extension identifier is 40 bits long.
extension identifier
A unique set of characters assigned to each NIC by its manufacturer. In the traditional, 48-bit physical addressing scheme, the extension identifier is 24 bits long. In EUI-64, the extension identifier is 40 bits long.
split DNS aka split-horizon DNS
An implementation of DNS where internal and external DNS queries are handled by different DNS servers or by a single DNS server that is specially configured to keep internal and external DNS zones separate.
Samba
An open source software package that provides complete Windows-style file- and printer-sharing capabilities.
shell prompt
Another term for the UNIX command interpreter.
authoritative servers
The authority on computer names and their IP addresses for computers in their domains.
name resolution
The process of discovering the IP address of a host when the FQDN is known.
Tunneling
The process of encapsulating one type of protocol in another. Tunneling is the way in which higher-layer data is transported over VPNs by Layer 2 protocols.
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.
Open source
The term that describes software whose code is publicly available for use and modification.
vim text editor
The text editing utility in Linux that allows a technician to make changes to text files, such as when editing the IP address range for a DHCP server.
canonical name
The true name of a server, such as www.example.com, as opposed to one of many alias names a server might have, such as ns1.example.com.
ipconfig
The utility used to display TCP/IP addressing and domain name information in the Windows client operating systems.
DHCPv6 aka DHCP6
The version of DHCP used with IPv6. DHCPv6 uses port number 546 for client-to-server communications and port number 547 for server-to-client communications.
ICMPv6
The version of ICMP used with IPv6 networks. ICMPv6 performs the functions that ICMP, IGMP, and ARP perform in IPv4. It detects and reports data transmission errors, discovers other nodes on a network, and manages multicasting.
ping6
The version of the ping utility used on Linux computers that run IPv6.
ping -6
The version of the ping utility used on Windows computers that run IPv6.
ifconfig
A TCP/IP configuration and management utility used with UNIX and Linux systems.
ping (Packet Internet Groper)
A TCP/IP troubleshooting utility that can verify that TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. Ping uses ICMP to send echo request and echo reply messages that determine the validity of an IP address.
nslookup (name space lookup)
A TCP/IP utility that allows a technician to query the DNS database from any computer on the network and find the host name of a network node by specifying its IP address, or vice versa. This ability is useful for verifying that a host is configured correctly and for troubleshooting DNS resolution problems.
elevated command prompt window
A command prompt window with administrative privileges.
gateway
A computer, router, or other device that a host uses to access another network. Gateways perform connectivity, session management, and data translation, so they must operate at multiple layers of the OSI model.
distributed database model
A database model in which data is distributed over multiple servers. In the case of DNS, for example, the records for host names and IP addresses are stored on thousands of servers around the globe so that DNS will not fail catastrophically if one or a handful of servers experience errors.
DNS cache
A database on a computer that stores information about IP addresses and their associated host names. DNS caches can exist on clients as well as on name servers.
firewall
A device (either a router or a computer running special software) that selectively filters or blocks traffic between networks.
Time to Live field
A field in a DNS resource record that identifies how long the record should be saved in a cache on a server. This field is included in zone transfers.
DNS (Domain Name System) aka Domain Name Service
A hierarchical way of tracking domain names and their addresses, devised in the mid-1980s. The DNS database does not rely on one file or even one server, but rather is distributed over several key computers across the Internet to prevent catastrophic failure if one or a few computers go down. DNS is a TCP/IP service that belongs to the Application layer of the OSI model.
computer name
A host name plus domain name that uniquely identifies a computer or location on a network.
fully qualified host name aka fully qualified domain name (FQDN)
A host name plus domain name that uniquely identifies a computer or location on a network.
Class A
A license for a single octet in an IPv4 address range. For example, the Class A license for 119 would acquire 119.0.0.0 through 119.255.255.255 IP addresses.
Class B
A license for the first two octets in an IPv4 address range. For example, the Class B license for 150.100 would acquire 150.100.0.0 through 150.100.255.255 IP addresses.
socket
A logical address consisting of a host's IP address and the port number of an application running on the host with a colon separating the two values. For example, if a host has an IP address of 10.43.3.87, the socket address for Telnet running on that host is 10.43.3.87:23.
DDNS (Dynamic DNS)
A method of dynamically updating DNS records for a host. DDNS monitoring software reports IP address changes to the DDNS service, which automatically updates DNS records.
interface
A network connection made by a node or host on a network.
hexadecimal number aka hex number
A number written in the base 16 numbering system, which uses the 16 numerals 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.
private port
A port assigned by a network administrator that is different from the well-known port number normally used for that service.
DNS zone
A portion of the DNS namespace for which one organization is assigned authority to manage.
DNS server
A server that contains a database of TCP/IP host names and their associated IP addresses. A DNS server supplies a resolver with the requested information. If it cannot resolve the IP address, the query passes to a higher-level DNS server.
name server
A server that contains a database of TCP/IP host names and their associated IP addresses. A DNS server supplies a resolver with the requested information. If it cannot resolve the IP address, the query passes to a higher-level DNS server.
bits
A single pulse in the digital encoding system that can have one of only two values: 0 or 1.
subnet
A smaller network within a larger network in which all nodes share a network addressing component and a fixed amount of bandwidth.
reservation
A static IP address assigned by DHCP.
base 8 numbering system aka octal number system
A system founded on using eight numbers (0 through 7) to encode information.
octal number system
A system founded on using eight numbers (0 through 7) to encode information.
binary number system aka base 2 number system
A system that uses 1s and 0s to encode information.
Network Address Translation (NAT)
A technique in which IP addresses used on a private network are assigned a public IP address by a gateway when accessing a public network.
zone file
A text file associated with a DNS zone that contains resource records identifying domains and their IP addresses.
zone files
A text file associated with a DNS zone that contains resource records identifying domains and their IP addresses.
DHCP (Dynamic Host Configuration Protocol)
An Application layer protocol in the TCP/IP suite that manages the dynamic distribution of IP addresses on a network. Using DHCP to assign IP addresses can nearly eliminate duplicate-addressing problems.
dynamic IP address
An IP address that is assigned to a device upon request and may change when the DHCP lease expires or is terminated. BOOTP and DHCP are two ways of assigning dynamic IP addresses.
link local address
An IP address that is automatically assigned by an operating system to allow a node to communicate over its local subnet if a routable IP address is not available. ICANN has established the range of 169.254.0.0 through 169.254.254.255 as potential link-local IPv4 addresses. IPv6 link-local addresses begin with the prefix FE80::/10.
static IP address
An IP address that is manually assigned to a device and remains constant until it is manually changed.
public IP address
An IP address that is valid for use on public networks, such as the Internet. An organization assigns its hosts public addresses from the range of addresses assigned to it by Internet numbering authorities.
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.
global unicast 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.
link local unicast address
An IPv6 address that can be used for communicating with nodes in the same link. These addresses are similar to IPv4's autoconfigured APIPA addresses and begin with the prefix FE80::/10.
DMZ (demilitarized zone)
An area on the perimeter of a network that is surrounded by two firewalls—an external firewall that is more porous to allow more types of access, and an internal firewall that is more hardened to provide greater protection to the internal network. DNS servers and Web servers are typically placed in the DMZ.
link
Any local area network (LAN) bounded by routers.
local link
Any local area network (LAN) bounded by routers.
private IP address
IP addresses that can be used on a private network but not on the Internet. IEEE recommends the following IP address ranges for private use: 10.0.0.0 through 10.255.255.255; 172.16.0.0 through 172.31.255.255; and 192.168.0.0 through 192.168.255.255.
subnet mask
In IPv4 addressing, a 32-bit number that helps one computer find another by indicating what portion of an IP address is the network portion and what portion is the host portion.
octets
One of the 4 bytes that are separated by periods and together make up an IPv4 address.
dynamic port
TCP/IP ports in the range of 49,152 through 65,535, which are open for use without requiring administrative privileges on a host or approval from IANA.
subnet ID
The 16 bits, or one block, in an IPv6 address that can be used to identify a subnet on a large corporate network.
EUI-64 (Extended Unique Identifier-64)
The IEEE standard defining 64-bit physical addresses. In the EUI-64 scheme, the OUI portion of an address is 24 bits in length. A 40-bit extension identifier makes up the rest of the physical address, for a total of 64 bits.
Internet Protocol version 4 (IPv4)
The Internet Protocol standard released in the 1980s and still commonly used on modern networks. It specifies 32-bit addresses composed of four octets.
well-known ports
The TCP/IP port numbers 0 to 1023, so named because they were long ago assigned by Internet authorities to popular services (for example, FTP and Telnet), and are, therefore, well known and frequently used.
registered ports
The TCP/IP ports in the range of 1024 to 49,151. These ports can be used by network users and processes that are not considered standard processes. Default assignments of these ports must be registered with IANA.
authoritative server
The authority on computer names and their IP addresses for computers in their domains.
resource records
The element of a DNS database stored on a name server that contains information about TCP/IP host names and their addresses.
namespace
The entire collection of Internet IP addresses and their associated names distributed over DNS name servers worldwide.
host name
The first part of an FQDN, such as www or ftp, which identifies the individual computer on the network.
default gateway
The gateway device that nodes on the network turn to first for access to the outside world.
top-level domain (TLD)
The last part of an FQDN and the highest-level category used to distinguish domain names—for example, .org, .com, and .net. A TLD is also known as the domain suffix.
domain name
The last two parts of an FQDN, such as mycompany.com. Usually, a domain name is associated with the company's name and its type of organization, such as a university or military unit.
6 to 4
The most common tunneling protocol that enables travel of IPv6 packets over IPv4 networks. IPv6 addresses intended to be used by this protocol always begin with the prefix 2002::/16.
BIND (Berkeley Internet Name Domain)
The most popular DNS server software. BIND is free, open source software that runs on Linux, UNIX, and Windows platforms.
Internet Corporation for Assigned Names and Numbers (ICANN)
The nonprofit corporation currently designated by the U.S. government to maintain and assign IP addresses.
neighbor
Two or more nodes on the same link.
alias
a nickname for a host
