Final answer:
The Internet Protocol (IP) layer or Network layer packages data into IP datagrams, containing source and destination address info, and performs routing of IP datagrams.
Step-by-step explanation:
The TCP/IP layer that packages data into IP datagrams, which contain source and destination address info that is used to forward the datagrams between hosts and across networks, and also performs routing of IP datagrams, is the Internet Protocol (IP) layer or Network layer.
The main responsibility of the IP layer is to provide logical addressing and routing of data between different networks. When data is passed down from the Transport layer to the Network layer, the IP layer adds a header to the data, creating an IP datagram. This header contains the source and destination IP addresses, which are used by routers to forward the datagram to its destination.
For example, if you send an email from your computer to another computer on a different network, the IP layer will package the email data into IP datagrams, assign source and destination IP addresses to these datagrams, and route them across the internet using routers until they reach their destination network.