Changes

[http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_9-1/autonomous_system_numbers.html Exploring Autonomous System Numbers]</ref> This means that the available quantity of ASN for internet routing is limited.

[http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_9-1/autonomous_system_numbers.html Exploring Autonomous System Numbers]</ref> This means that the available quantity of ASN for internet routing is limited.

==Definition of Autonomous System (AS)==

==Autonomous System (AS)==

Based on RFC 4271, '''Autonomous System (AS)''' is defined as a set of routers under a single technical administration, using an interior gateway  protocol (IGP) and common metrics to determine how to route packets within the AS, and using an inter-AS routing protocol to  determine how to route packets to other ASes.The [[NWG|Network Working Group]] explained that since the introduction of this definition, several IGP is commonly used for a single AS and several sets of metrics within an AS is sometimes used. The NWG also explained that the administration of an AS to other ASes still emerge with a single coherent interior routing plan and a consistent picture of the destinations that are reachable through it even when multiple IGPs and metrics are utilized.<ref>[http://tools.ietf.org/html/rfc4271 RFC 4271- A Border Gateway Protocol 4]</ref>

Based on RFC 4271, '''Autonomous System (AS)''' is defined as a set of routers under a single technical administration, using an interior gateway  protocol (IGP) and common metrics to determine how to route packets within the AS, and using an inter-AS routing protocol to  determine how to route packets to other ASes.The [[NWG|Network Working Group]] explained that since the introduction of this definition, several IGP is commonly used for a single AS and several sets of metrics within an AS is sometimes used. The NWG also explained that the administration of an AS to other ASes still emerge with a single coherent interior routing plan and a consistent picture of the destinations that are reachable through it even when multiple IGPs and metrics are utilized.<ref>[http://tools.ietf.org/html/rfc4271 RFC 4271- A Border Gateway Protocol 4]</ref>