What protocol is often used between gateway hosts on the Internet?

 Border Gateway Protocol (BGP) is a protocol that is often used between gateway hosts on the Internet. A gateway host is a network device that connects two or more different networks, such as a router or a firewall. BGP is a routing protocol that exchanges routing information between autonomous systems (ASes), which are groups of networks under a single administrative control. BGP is used to determine the best path to reach a destination network on the Internet, based on various factors such as hop count, bandwidth, latency, and policy. BGP is also used to implement interdomain routing policies, such as traffic engineering, load balancing, and security. BGP is the de facto standard for Internet routing and is widely deployed by Internet service providers (ISPs) and large enterprises. The other options are not protocols that are often used between gateway hosts on the Internet. Exterior Gateway Protocol (EGP) is an obsolete protocol that was used to exchange routing information between ASes before BGP. Open Shortest Path First (OSPF) is a protocol that is used to exchange routing information within an AS, not between ASes. Internet Control Message Protocol (ICMP) is a protocol that is used to send error and control messages between hosts and routers, not to exchange routing information. References: Border Gateway Protocol - Wikipedia; What is Border Gateway Protocol (BGP)? - Definition from WhatIs.com; What is BGP? | How BGP Routing Works | Cloudflare.