This is a very large domain. Even if you are a “networking person,” do not blow this domain off.
I know networking gurus who have failed the exam because of this domain!
OSI Model – Open Systems Interconnection model, a networking model that breaks networking into 7 layers. Essentially theoretical today but often referred to. You must know the layers for the exam!
NIC – Network Interface Card.
MAC address – Media Access Control address, a unique hardware address assigned to a network interface, commonly burnt into a NIC at manufacture time.
LLC – Logical Link Control. LLC is the upper part of Layer 2 in the OSI model and acts as the interface between Media Access Control (MAC) and Layer 3, the Network Layer. It handles flow control, error checking, and the multiplexing of protocols over the MAC Layer, allowing multiple disparate network protocols to be used simultaneously, for example IP and AppleTalk.
IP – Internet Protocol. The main protocol of the Internet. A layer 3 protocol. There are two versions of IP, IPv4 and IPv6. IPv4 is currently dominant.
Private Networking Addressing – An Internet standard (RFC1918) that allows the network address ranges 10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255, and 192.168.0.0-184.108.40.206 to be used in private Internets and does not allow them to be routed over the public Internet. A host with a private network address typically is allowed to access the public Internet using Network Address Translation (NAT).
NAT – Network Address Translation.
CIDR – Classless Inter-Domain Routing. A method for allocating (and routing) IP addresses that extends IP addresses beyond classful addressing (e.g. Class A, B, and C).
DNS – Domain Name System, a hierarchical distributed naming system for converting names like securitycerts.org to IP addresses and vice-versa.
UDP – User Datagram Protocol. A layer 4 protocol.
TCP – Transmission Control Protocol. A layer 4 protocol.
ICMP – Internet Control Message Protocol. A layer 3 protocol like IP, but carried in an IP packet like UDP and TCP.
MIME – Multipurpose Internet Mail Extensions. An Internet standard for the format of email that allows non-ASCII character sets, non text attachments, and more. Essentially all Internet email is in MIME format.
S/MIME – Secure/Multipurpose Internet Mail Extensions, a standard for email encryption and digital signature based on digital certificates. Supported by most modern email clients like Thunderbird and Microsoft Outlook.
HTTP – Hypertext Transfer Protocol. An application protocol that is the foundation of the web.
S-HTTP – Secure Hypertext Transfer Protocol. A protocol for encrypting web communications that is considered legacy and was never much used. HTTPS is used instead.
HTTPS – HTTP over SSL/TLS. Widely used.
SET – Secure Electronic Transaction. A protocol for transferring credit card information over insecure networks like the Internet. A legacy protocol that never took off.
PEM – Privacy Enhanced Mail. A standard for securing email that never became popular. S/MIME is used instead.
FTP – File Transfer Protocol, a clear text protocol that is widely used but that passes passwords and usernames in clear text over the network.
TFTP –Trivial File Transfer Protocol. A simplified version if FTP most commonly used for transferring configuration or boot files over LANs.
SMTP – Simple Mail Transfer Protocol, the Internet standard for email transmission over IP.
SNMP – Simple Network Management Protocol.
DNP3 – Distributed Network Protocol. Mainly used in SCADA systems by electric and water companies. An example of a multi-layer protocol. DNP3 is layer 2 and layer 7 and arguably layer 4 as well.
DASD – Direct Access Storage Device. Secondary storage directly attached to a host computer. Examples include internal and external device drives connected via IDE, SATA and other interfaces. Allows direct block level access.
NAS – Network Attached Storage. File and directory access, usually over Ethernet. Direct block level access is not possible.
SAN – Storage Area Network. The network equivalent to directly attached storage. Allows direct block level access.
IDE – Integrated Drive Electronics. Western Digital's original interface specification for the attachment of storage devices. Used for directly attached storage.
SATA – Serial AT Attachment, A more modern interface specification for the attachment of storage devices than IDE. Used for directly attached storage.
SCSI – Small Computer System Interface. SCSI consists of a set of standards for connecting and transferring data between computers and hard drives, tape drives, and other peripheral devices. Used for directly attached storage.
iSCSI – Internet Small Computer System Interface. SCSI over IP networks. A Storage Area Network (SAN) protocol. Uses normal network cabling.
Fibre Channel – A high speed network technology used primarily as a Storage Area Network (SAN) protocol.
FCoE – Fibre Channel over Ethernet. A Storage Area Network (SAN) protocol. Runs directly on Ethernet, not IP, hence not IP routable.
FCIP - Fibre Channel over IP. FCIP encapsulate Fibre Channel frames and forwards them over IP.
VOIP – Voice Over IP, which interestingly is considered a WAN protocol by ISC2.
PSTN – Public Switched Telephone Network. The legacy phone network.
PBX – Private Branch Exchange. A phone switch. Many legacy PBXs are so large you can actually walk into them.
FXS Adaptor– Foreign eXchange Subscriber (or Service or System) Adaptor, also known as an ATA (Analog Telephone Adaptor). Used to connect an analog phone or FAX to VOIP.
SIP – Session Initialization Protocol. A VOIP signaling protocol for setting up and tearing down VOIP calls, locating users, and negotiating common protocols. The other VOIP signaling protocol is the much more complex H.323.
RTP – Real Time Protocol. The VOIP protocol that carries digitized voice. Can also carry digitized video.
SRTP – Secure Real Time Protocol. Currently in draft (Dec 2015), SRTP adds encryption, authentication, message integrity and replay protection to RTP.
RTCP – Real Time Control Protocol, used in conjunction with the RTP to carry statistics, quality of service information, and more.
VTC – Video Teleconferencing. Commonly uses VOIP protocols.
IM – Instant Messaging.
RDP – Remote Desktop Protocol. A Microsoft protocol for Remote Assistance/troubleshooting and Remote Desktop Services which lets admins control remote servers. Allows a user to connect to a remote computer via a GUI.
VNC – Virtual Network Computing. Similar conceptually to RDP above but platform independent.
NFC – Near Field Communications. Wireless protocol that allows smart phones and other devices to communicate when very close to each other, commonly touching or within very few inches apart.
WEP – Wired Equivalent Privacy. The original Wi-Fi (IEEE 802.11 wireless networks) security protocol. Depreciated as it is very weak and has numerous flaws.
WPA – Wi-Fi Protected Access, and WPA2, Wi-Fi Protected Access II, replacements for WEP.
TKIP –Temporal Key Integrity Protocol. WPA, but NOT WPA2, uses TKIP.
LAN – Local Area Network. A bunch of computers electronically close to each other, typically used to mean within one broadcast domain, i.e. they can broadcast to each other. From the security standpoint, the LAN is also a security demarcation perimeter as if you are in a LAN you are fundamentally more trusted than if you are not in the LAN.
WAN – Wide Area Network. A bunch of LANs connected together via a (usually high speed) backbone.
MAN – Metropolitan Area Network. As in “What’s bigger than a LAN but smaller than a WAN? A MAN.” Term is not used that often anymore.
GAN – Global Area Network. A big WAN. The biggest GAN is obviously the Internet. At least on this planet.
PAN – Personal Area Network. A small number of personal devices connected via a network, for example your phone, tablet, and your dorky ear piece via Bluetooth.
DMZ – DeMilitarized Zone, the Internet accessible part of an organization's network.
ATM – Asynchronous Transfer Mode. An older protocol which is typically used as a high speed backbone connecting LANs together, although it also can be used as a LAN protocol. Frames are 53 bytes, 48 of data and 5 of header. Elegant design based on the technologies and limitations of the day or an odd bastard designed by committee? Perhaps a bit of both.
FDDI – Fiber Distributed Data Interface. A token ring based network. It contains two fiber based rings, one as a backup for the other. Considered legacy as fast Ethernet and other technologies have eclipsed it.
SDLC – Synchronous Data Link Control. An old mainframe protocol. Think IBM’s SNA, System Network Architecture. A layer 2 protocol. Pretty rare these days as IP has taken over the world.
HDLC – High-Level Data Link Control. A bit-oriented synchronous data link layer protocol based on SDLC (above). I think of it as the protocol that moves data over an X.25 or Frame Relay cloud.
ISDN – Integrated Services Digital Network, or perhaps “It Still Does Nothing.” A “faster than modem” technology that works over standard copper telephone lines. Never really took off at least in North America, since DSL and Cable Modem came around the same time and are much faster, but still used for some purposes including video teleconferencing and popular in parts of Europe and India as well.
X.25 – A WAN technology popular in the 1980s and still in use. Primarily legacy.
Frame Relay – A WAN technology similar to X.25 but without extensive error checking as modern networks are reliable. Primarily legacy.
CSMA – Carrier Sense Multiple Access.
CSMA/CD – Carrier Sense Multiple Access with Collision Detection, used for example by Ethernet.
CSMA/CA – Carrier Sense Multiple Access with Collision Avoidance, used for example by Wi-Fi.
DSL – Digital Subscriber Line.
ASDL – Asymmetric Digital Subscriber Line. Faster download speeds than
SDSL – Single Line Digital Subscriber Line – Symmetrical download and upload rates of 1.544 mbps. An operating range of 10,000 feet from the phone company’s central switching equipment.
HDSL – High Rate Digital Subscriber Line. Like SDSL but uses two pairs of twisted copper lines instead of one to give a 12,000 feet operating range at 1.544mps symmetric. Sometimes used to implement a T1 line.
VDSL – Very high rate Digital Subscriber Line. Asymmetric, downstream rates of 13 to 52 mbps and upstream rates of 1.5 to 2.3 mbps, Short range, only 1000 to 4,500 feet from the phone company’s central switching equipment.
QoS – Quality of Service. The concept that network bandwidth can be reserved, for example by an application. In reality, QoS encompasses far more than just bandwidth, including response time, loss, signal-to-noise ratio, echo, interrupts, frequency response, and more.
Circuit Switching - A circuit switched network establishes a dedicated communications channel, called a circuit, between two network nodes before they can communicate. The legacy phone network (PSTN) is an example of a circuit switched network.
Packet Switching - In a packet switched network, data is separated into little pieces called "packets" which are transmitted independently though the network. Each packet may take a different route. Also, there are no dedicated communication channels, and different connections may compete for bandwidth on a given communication channel. IP is an example of a packet switched networking technology.
VC – Virtual Circuit. A virtual circuit simulates a circuit over a packet switched network.
SVC – Switched Virtual Circuit.
PVC – Permanent Virtual Circuit.
DTE – Data Terminal Equipment, any device connected to a network like a workstation, server, router, bridge, etc.
DCE – Data Communication Equipment or Data Circuit-Terminating Equipment, a hardware device that sits between a DTE and the data transmission circuit. One example of a DCE is a modem.
DSU/CSU – Data Service Unit/Channel Service Unit. A modem sized hardware device that connects a DTE (like a router) to a digital circuit like a T1 or T3 line. A DSU/CSU is an example of a DCE.
VLAN – Virtual Local Area Network.
ARP – Address Resolution Protocol, resolves between network addresses and link layer addresses, for example between IP addresses and MAC addresses.
RARP – Reverse Address Resolution Protocol, resolves between link layer addresses and network addresses.
RIP – Routing Information Protocol, a simple routing protocol that solely uses hop count as the distance metric. The fewer hops, the closer something is, and it ignores any other factors such as network speeds etc.
OSPF – Open Shortest Path First, a common routing protocol that is more advanced and complex than RIP.
EGP – Exterior Gateway Protocol. A routing protocol used to exchange information between autonomous systems, for example BGP below.
BGP – Border Gateway Protocol, a very commonly used routing protocol between autonomous systems on the Internet. Basically the "glue" that holds the Internet together.
MPLS – Multiprotocol Label Switching. A common way of providing WAN access between networks.
SDN – Software Defined Networking. The concept of controlling a router’s control plane (which includes routing updates, time synchronization, logging and more) remotely/centrally instead of on a granular per router basis.
CDN – Content Distribution Network. Examples include CloudFlare and Akamai.
VPN – Virtual Private Network.
RADIUS – Remote Authentication Dial In User Service.
Diameter – A draft specification for a replacement for RADIUS servers that overcomes many limitations of RADIUS. I've never seen a Diameter server. Do they actually exist?
TACACS – Terminal Access Controller Access Control System.
PAP – Password Authentication Protocol, an early protocol that sends the username and password over the network in clear text. For example, some (legacy) RADIUS servers use PAP.
CHAP – Challenge Handshake Authentication Protocol, a protocol that does not send the password over the network. Some RADIUS Servers use CHAP.
EAP – Extensible Authentication Protocol, an authentication framework used with PPP, wireless, and more. There are many EAP protocols, over 100. Some RADIUS Servers use EAP.
802.1x – An IEEE standard which separates physical access to a network from logical access. Physically connecting to a network, i.e. OSI Layer 1, for example by physically plugging into a network switch or connecting to a 802.11 Wi-Fi network, does not guarantee logical access. Numerous checks can be done before allowing logical access.
NAC – Network Access Control. At its simplest, NAC is 802.1x. Most people however agree that NAC goes above and beyond simple 802.1x (although you may hear the terms used interchangeably at times). NAC adds more control to 802.1x, and allows defining granular policies. These can include pre admission controls and post admission controls such as where users/devices are allowed on the network and what they are authorized to do.
SLIP – Serial Line Internet Protocol. A protocol for relaying IP packets over dialup lines. Mostly replaced by PPP.
PPP – Point to Point Protocol, used for dialup connections to the Internet, including ISDN and cellular modems.
NTP – Network Time Protocol.
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