ARP

Address Resolution Protocol

Using broadcast packets, ARP allows for devices to map IP addresses against MAC addresses. This protocol uses both L2 & L3 of the OSI model. For example:

arp -a

192.168.1.1 - 9C-35-3A-9B-8A-AF

ARIN

American Registry for Internet Numbers

Alongside global counterparts ARIN is responsible for distributing IP subnets to the US, Canada and surrounding area.

ACK

Acknowledgement

Always found within TCP session creation at the synchronization stage. ACKs are also sent after a data segment is received by the client (depending on the TCP method used).

AES

Advanced Encryption Standard

Released in 2001 as a replacement for DES, AES allows for extremely strong cryptographic encryption of data. It is used for both data transmission and data storage.

Application Layer

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This is the 7th layer of the OSI model, and is ultimately the point of which the data that has been transmitted across the network is provided to the user. Examples of application layer protocols are:

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HTTPS // SMTP // FTP // POP3

ASN

Autonomous System Number

An autonomous system is a large network managed by a service provider. These service providers then peer with each other to allow traffic to forward through their network. Ultimately, this peering of ASs makes up the wider internet and allows you to use services in the US from Europe.

ATM

Asynchronous Transfer Mode

Protocol usually found in broadband networks, allows for transmission of data across telecom provider networks.

ACL

Access Control List

A rule based, hierarchical list that can be used to define whether ingress or egress traffic is permitted (or denied) into the network. There are 4 different types of ACL; Standard, Dynamic, Extended and Reflexive.

ADSL

Assymetric Digital Subscriber Line

Used to send data across a copper pair supplied by a telecoms provider's telephone network. There are 3 different types of ADSL:

 - ADSL (12Mbps down, 1.3Mbps up)

 - ADSL2 (12Mbps down, 3.5Mbps up)

 - ADSL2+ (24Mbps down, 3.3Mbps up)

Anycast

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Anycast IP addresses are shared across multiple devices, usually on a global scale to ensure that content is loaded from the closet node. It also allows for resiliency due to multiple IPs being presented onto the internet. 

ASIC

Application Specific Integrated Circuit

An ASIC is a hardware designed chipset with a specific application in mind. For example in a standard layer 2 switch, an ASIC may be used for very fast forwarding of frames to their dedicated interface, rather than using software on a standard CPU.