Internet Protocol (IP) defines how communication occurs between two computers within the network layer of a networked system. To understand the concept of “best-effort delivery” it’s important to recognize some fundamental underpinnings of IP protocol (RFC 791):
- IP is a connectionless system; every packet sent across the network is treated as a unique entity. IP doesn’t recognize that 15 packets are 15 parts of the same data source—it just sends them where they need to go.
- IP does not guarantee reliable data delivery. Packet loss, bit corruption, and other issues may arise based on network conditions
TL;DR – IP protocol doesn’t know what it’s sending and can’t guarantee that it will get there.
These two concepts help frame the larger notion of IP being a “best-effort” system. This means that, as outlined by IP protocols, the network will treat all packets equally in the effort to make delivery. However, when network conditions degrade, things like packet loss may occur.
Given such conditions are unpredictable, the best assertion IP can make to the status of data transmission is that it was given the network’s best effort. For a more detailed discussion of best-effort delivery services read the 2008 RFC5290 titled Comments on the Usefulness of Simple Best-Effort Traffic.