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Across 2. The session, presentation, and application layers are the ____ support layers. 5. The _______ model shows how the network functions of a computer ought to be organized. 8. The physical layer is concerned with the movement of _______ over the physical medium. 10. The ____ created a model called the Open Systems Interconnection, which allows diverse systems to communicate. 12. As the data packet moves from the upper to the lower layers, headers are _______. 13. In the OSI model, encryption and decryption are functions of the ________ layer. 17. Ethernet uses a ______ physical address that is imprinted on the network interface card (NIC). 18. The _______ layer lies between the network layer and the application layer. 21. The _______ layer coordinates the functions required to transmit a bit stream over a physical medium. 22. The ______ layer establishes, maintains, and synchronizes the interactions between communicating devices. 23. The ______ layer is responsible for moving frames from one hop (node) to the next. (2 Words) 25. The _______ layer changes bits into electromagnetic signals. 27. Layer 2 lies between the physical layer and the _______ layer. 28. The ____ address uniquely defines a host on the Internet. 30. The _______ layer ensures interoperability between communicating devices through transformation of data into a mutually agreed upon format. 31. The ________ layer is responsible for the process-to-process delivery of the entire message. 33. The ______ layer is responsible for the source-to-destination delivery of a packet across multiple network links. 34. __________ provides full transport layer services to applications. 35. The TCP/IP _______ layer is equivalent to the combined session, presentation, and application layers of the OSI model. 37. The Internet model consists of _______ layers. 38. To deliver a message to the correct application program running on a host, the _______ address must be consulted. 39. The _________ layer enables the users to access the network.

Down 1. The seven-layer _____ model provides guidelines for the development of universally compatible networking protocols. 3. In the OSI model, as a data packet moves from the lower to the upper layers, headers are _______. 4. When a host on network A sends a message to a host on network B, which address does the router look at? 6. The OSI model consists of _______ layers. 7. The process-to-process delivery of the entire message is the responsibility of the _______ layer. 9. The_________ layer is responsible for the delivery of a message from one process to another. 11. TCP/IP is a ______ hierarchical protocol suite developed ____ the OSI model. (2 Words) 14. A port address in TCP/IP is ______ bits long. 15. The ______ layer adds a header to the packet coming from the upper layer that includes the logical addresses of the sender and receiver. 16. In the OSI model, when data is transmitted from device A to device B, the header from A's layer 5 is read by B's _______ layer. 19. When data are transmitted from device A to device B, the header from A's layer 4 is read by B's _______ layer. 20. The _______ layer is responsible for delivering data units from one station to the next without errors. (2 Words) 24. The _______ layer is the layer closest to the transmission medium. 25. The ________ address, also known as the link address, is the address of a node as defined by its LAN or WAN. 26. Mail services are available to network users through the _______ layer. 29. The _______ layer links the network support layers and the user support layers. 32. The physical, data link, and network layers are the ______ support layers. 36. _______ is a process-to-process protocol that adds only port addresses, checksum error control, and length information to the data from the upper layer.