Predators & defenses : Many different types of animals prey on adult sea urchins, including birds, sea otters, fishes, crabs, lobsters, octopuses, and sea stars. Eggs and larvae of sea urchins are eaten by many types of carnivorous zooplankters and by suspension-feeding invertebrates including hydroids, sea anemones, and mussels, just to name a few.
IPv4 (Internet Protocol Version 4) is the fourth revision of the Internet Protocol (IP) used to to identify devices on a network through an addressing system. The Internet Protocol is designed for use in interconnected systems of packet-switched computer communication networks (see RFC:791).
Ethernet is one example protocol at the TCP/IP network access layer. Each layer provides services to the layer above it in the model. (TCP/IP and OSI models) IP, an TCP/IP Internet Layer, relies on the network access layer to deliver IP packets across a physical network. The network access layer includes a large number of protocols, such as Ethernet, PPP, IPSEC, Frame Relay, etc.