IP Transit is a service provided by Internet Service Providers (ISPs) that enables traffic to travel across their network infrastructure to reach the rest of the Internet. It is a crucial component in the functioning of the Internet, as it allows for the exchange of traffic between different networks using the Border Gateway Protocol (BGP). IP Transit is typically used by organizations that operate their own Autonomous System (AS) and have an Autonomous System Number (ASN), which is necessary to establish routing with BGP.
Autonomous Systems and BGP
An Autonomous System (AS) is a network or group of networks under a common administration that presents a common routing policy to the Internet. Each AS is identified by a unique ASN, which is used to exchange routing information with other ASes. BGP is the protocol that facilitates this exchange, allowing different networks to communicate and transfer data across the Internet.
IP Transit vs. Peering
IP Transit should not be confused with peering. While peering is an arrangement where networks exchange traffic on a mutual benefit and often cost-neutral basis, IP Transit is a commercial service. In IP Transit, one network pays another network to access not just its own routes but the entire Internet routing table or a significant subset of it. This service is typically charged based on usage or a flat monthly fee.
Service Level Agreements (SLAs)
IP Transit services often come with SLAs that define the quality of service and provide terms for reimbursement in case the customer cannot access the Internet as agreed. The pricing for IP Transit is usually per megabit per second per month, and the cost can vary depending on factors like volume discounts and commitment levels.
Who Uses IP Transit?
IP Transit is used by companies, ISPs, and large organizations that require high-speed, reliable connectivity to the Internet. It is particularly important for those who need to transfer large amounts of data or host services online. The service is essential for ISPs that do not have their own global IP backbone network, as it allows them to offer full Internet access to their customers.
Conclusion
In summary, IP Transit is a paid service that enables networks to connect to the rest of the Internet through a transit provider using BGP. It is a fundamental service for the operation of the Internet, especially for entities that manage their own AS and need to ensure reliable and fast connectivity for their users.