Description: The AS NUMBER, or Autonomous System Number, is a unique identifier assigned to each Autonomous System (AS) in the context of the Border Gateway Protocol (BGP). An Autonomous System is a collection of IP addresses and networks under the control of a single administrative entity, such as an Internet Service Provider (ISP) or an organization. The AS NUMBER allows BGP to identify and manage traffic routes between different autonomous systems on the Internet, facilitating communication and information exchange between them. This number can be either 16 bits (type 1 AS) or 32 bits (type 2 AS), allowing for a wide range of unique identifiers. The assignment of AS NUMBER is managed by the Internet Assigned Numbers Authority (IANA) and regional Internet registry organizations (RIRs). Proper use of the AS NUMBER is crucial for the efficient functioning of BGP, as it ensures that routes are established correctly and that traffic is directed appropriately across the vast Internet network.
History: The concept of Autonomous System and its corresponding AS NUMBER emerged in the 1990s with the development of the Border Gateway Protocol (BGP). BGP was designed to address routing issues on the Internet, allowing different networks to communicate more efficiently. As the Internet grew, there was a need to establish an identification system that would enable routers to exchange routing information effectively. In 1994, BGP-4 was introduced, allowing the use of 32-bit AS NUMBERS, significantly expanding the available address space.
Uses: The AS NUMBER is primarily used in Internet routing to uniquely identify each Autonomous System. This allows BGP routers to exchange information about available routes and make decisions on how to direct traffic. Additionally, the AS NUMBER is essential for implementing routing policies, as it enables network administrators to control how routes are handled between different autonomous systems.
Examples: An example of an AS NUMBER is AS15169, which belongs to Google. This number allows routers to identify the routes that belong to Google’s network and manage the traffic passing through it. Another example is AS32934, which corresponds to Facebook, facilitating the routing of data to and from its servers.
