This is an attempt to collect all the necessary basic vocabulary to have a very basic basic understanding of networking. Because context is also needed, some concepts or historical references will be also shown. This dictionary is an informal one, for a better, accurate, more correct and in depth understanding look somewhere else, like the provided links.
Packet. A packet is a formatted unit of data consisted by a header and a payload.
Datagram. It’s a basic transfer unit on a packet-switched network. They are composed by a header and a payload.
Header. A header is a control unit, which is also data, but used to direct packets and/or give specific instructions about other data (payload).
Payload. Another way of meaning data, but in the context of being transported through a network.
Packet switching. A kind of digital network where data is grouped by packets. The channel is only occupied during the transmission of packets, reamining free at the end of their transit. One characteristic is being able to send data at a variable bit rate stream.
Internet Protocol Suite (TCP/IP). It is a conceptual model of serveral communication protocols which specify how data ought to be packed, addressed, transmitted, routed and received. The TCP and IP protocols are the foundations of the suite.
Transmission Control Protocol (TCP). Part of the Internet Protocol Suite. This is the protocol in charge of octets (bytes) sent through an IP network. The protocol ensures data order, is not corrupted (error checking) and all is done reliably. Therefore TCP is considered a protocol for applications that require a reliable data stream. TCP detects problems such as lost of packets, network congestion, out of order delivery of packets and corrects these issues. If the data can’t reach its destination the source is notified. Because of the control of the stream on this protocol it’s not very suitable for live streaming events.
User Datagram Protocol (UDP). Part of the Internet Protocol Suite. This procotol uses a simple connectionless communication model providing checksums for data integrity, port numbers to address different functions at the source and destination, it has no handshaking dialogues and as a consequence there is no guarantee of the delivery ordering or duplicates. It usually exposes program defficiencies, unless the program does the missing functions. It’s lack of full control over the stream, packets may drop but the connection isn’t interrupted, since the destination isn’t waiting for missing packets, making it a good choice for real time systems.
Internet Protocol (IP). It is the main communication protocol in the Internet Protocol Suite. It relays datagrams accross network boundaries. That is to say it interconnects different networks, therefore this is the internet pilar system. The main task is delivering packets from a source to a destination only based on the IP found in the packet header. Its main version is IPv4 and IPv6 is its successor, although the former is the most relevant still.
Internet Protocol version 4 (IPv4). It’s a connectionless protocol operating under the best effort delivery model, not granting the packet delivery nor assuring a proper sequencing or avoidance of duplicate delivery. The protocol uses 32-bit addresses and although the limit of the number of addresses was thought as sufficient back on the day, a little more than 4,2 billion addresses hasn’t been enough. A portion of those adresses have been reserved for private uses. That with the help of Network Address Translation has helped the continuate use of IPv4 instead of going straight away to IPv6.
Internet Protocol version 6 (Ipv6). The most recent version of the IP protocol. It’s been developed to superseed the IPv4 version, the main reason the exhaustion of IPv4 addresses. Instead of using 32 bits addresses it climbs up to 128. It does also bring optimizations on security and configuration aspects. Despite all this its adoption is still low although it’s being adopted more frequently in recent times.
Network Address Translation (NAT). A method to change the IP header of a packet so it is redirected to another destination. It was inteded as a method not to modify a network topology any time hosts were changed but it’s been a key to solve the exhaustion of IPv4 addresses problem. It often relies on the reserved addresses set by the IEFT and IANA. The public address for a specific website may be 52.96.xx.xx, however the web server sitting in the LAN (Local Area Network) which is in charge of serving the website has a different IP address, typically a reserved one such as 192.168.54.64. The router at the edge of the LAN listens and serves content at 52.96.xx.xx in the outside, but it does it in a different IP range inside.
Dynamic Host Configuration Protocol (DHCP). A protocol used to dynamically assign IP addresses on UDP/IP networks.
Domain Name System (DNS). It is a system to relate domain names to specific IP addresses. It is hierarchical and decentralized and it works as a distributed directory service for computers on the internet or local networks. It is also related to services and protocols for a domains, such as email.
7. Application layer
6. Presentation layer
5. Session layer
4. Transport layer
3. Network layer
2. Data link layer
1. Physical layer
Some protocols related to each layer:
7. Application layer
NNTP SIP SSI DNS FTP Gopher HTTP NFS NTP SMPP SMTP SNMP Telnet DHCP Netconf more….
6. Presentation layer
MIME XDR ASN.1
5. Session layer
Named pipe NetBIOS SAP PPTP RTP SOCKS SPDY
4. Transport layer
TCP UDP SCTP DCCP SPX
3. Network layer
IPv4 IPv6 ICMP IPsec IGMP IPX AppleTalk X.25 PLP
2. Data link layer
ATM ARP IS-IS SDLC HDLC CSLIP SLIP GFP PLIP IEEE 802.2 LLC MAC L2TP IEEE 802.3 Frame Relay ITU-T G.hn DLL PPP X.25 LAPB Q.922 LAPF
1. Physical layer
EIA/TIA-232 EIA/TIA-449 ITU-T V-Series I.430 I.431 PDH SONET/SDH PON OTN DSL IEEE 802.3 IEEE 802.11 IEEE 802.15 IEEE 802.16 IEEE 1394 ITU-T G.hn PHY USB Bluetooth RS-232 RS-449
Network Interface Controller (NIC). Computer hardware component that connects a computer to a computer network. Most desktop computers have an Ethernet NIC already built into the motherboard although expansion cards can be used to have more ports.
Network Switch. A device for networking purposes, mainly to connect other devices to it, and transfer the packets from those to a router, gateway or other switches. There are several types, and some work in specific layers of the OSI model.
A layer 1 network device transfers data, but does not manage any of the traffic coming through it, an example is Ethernet hub.
A layer 2 network device is a multiport device that uses hardware addresses, MAC address, to process and forward data at the data link layer (layer 2).
A layer-3 switch can perform some or all of the functions normally performed by a router.
Layer 4. While the exact meaning of the term layer-4 switch is vendor-dependent, it almost always starts with a capability for network address translation, and may add some type of load distribution based on TCP sessions or advanced QoS capabilities.
Layer-7 switches may distribute the load based on uniform resource locators (URLs), or by using some installation-specific technique to recognize application-level transactions. A layer-7 switch may include a web cache and participate in a content delivery network (CDN)
Routing schemes differ in how they deliver messages:
- unicast delivers a message to a single specific node
- broadcast delivers a message to all nodes in the network
- multicast delivers a message to a group of nodes that have expressed interest in receiving the message
- anycast delivers a message to any one out of a group of nodes, typically the one nearest to the source
- geocast delivers a message to a group of nodes based on geographic location
Unicast is the dominant form of message delivery on the Internet. This article focuses on unicast routing algorithms.
IP routing. It is the field of routing methodologies of Internet Protocol (IP) packets within and across IP networks.
Local Area Network (LAN). A LAN is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.
Wide Area Network (WAN). A WAN is a telecommunications network that extends over a large geographical area for the primary purpose of computer networking. Wide area networks are often established with leased telecommunication circuits.
Border Gateway Protocol (BGP). Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. The protocol is classified as a path vector protocol. The Border Gateway Protocol makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator and is involved in making core routing decisions.
IEEE 802. IEEE 802 is a family of IEEE standards dealing with local area networks and metropolitan area networks. More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets.
Ethernet. Ethernet is a family of computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). The original 10BASE5 Ethernet uses coaxial cable as a shared medium, while the newer Ethernet variants use twisted pair and fiber optic links in conjunction with switches.
Point-to-Point Protocol (PPP). Point to Point Protocol is a data link layer (layer 2) communications protocol used to establish a direct connection between two nodes. It connects two routers directly without any host or any other networking device in between. It can provide connection authentication, transmission encryption and compression.
Digital Subscriber Line (DSL). DSL is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access.
Medium Access Control (MAC). The medium access control (MAC) sublayer is the layer that controls the hardware responsible for interaction with the wired, optical or wireless transmission medium. The MAC sublayer and the logical link control (LLC) sublayer together make up the data link layer. Within the data link layer, the LLC provides flow control and multiplexing for the logical link (i.e. EtherType, 802.1Q VLAN tag etc), while the MAC provides flow control and multiplexing for the transmission medium.
Internet Control Message Protocol (ICMP). ICMP is a supporting protocol in the Internet Protocol Suite. It is used by network devices, including routers, to send error messages and operational information indicating, for example, that a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute).
Network Time Protocol (NTP). NTP is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. The protocol is usually described in terms of a client-server model, but can as easily be used in peer-to-peer relationships where both peers consider the other to be a potential time source
Secure Shell (SSH). SSH is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH.
Hypertext Transfer Protocol (HTTP). The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, where hypertext documents include to other resources that the user can easily access, for example by a mouse click or by tapping the screen in a web browser. HTTP was developed to facilitate hypertext and the World Wide Web.
Secure Socket Layer (SSL) / Transport Layer Security (TLS). SSL and the more modern TLS are cryptographic protocols designed to provide communications security over a computer network. Several versions of the protocols find widespread use in applications such as web browsing, email, instant messaging, and voice over IP (VoIP).
IETF New to the internet, FAQ’s:
IBM Redbooks, TCP/IP Tutorial and Technical Overview: