 format for the Internet layer. Routing of packets to avoid congestion is also handled in the Internet layer. This is a key layer of the TCP/IP model and all data has to pass this layer before being sent to lower layers for transmission. 4. Network interface layer: The physical layer and data link layer of the OSI model are grouped into a single layer called network interface layer in the TCP/IP model. This layer is used by the TCP/IP protocols running at the Seven-Layer Communication Model upper layers to interface with the local network. The TCP/IP model does not give much detail on the implementation or the specific set of functions to be performed at the network interface layer except it being the point for connection of host to network and use of an associated protocol to trans- mit IP packets. Protocols like point-to-point protocol (PPP) and serial line Internet protocol (SLIP) can be considered protocols of the network interface layer. The actual protocol used in the network interface layer varies from host to host and network to network. The network interface layer is also called the network access layer. In some implementations of the network interface layer, it performs functions like frame synchronization, control of errors, and media access. There are some significant differences between the OSI model and TCP/IP model. In the TCP/IP model, reliability is mainly handled at the transport layer. The transport layer takes on all functions for handling data transfer reliabil- ity, which includes capabilities like error detection and recovery, checksums, acknowledgments, and timeouts. The other difference is the presence of intelligent hosts when using a TCP/ IP model. This means that an OSI model does not handle management of network operations while most TCP/IP implementations like Internet have capabilities to manage network operations, which make them intel- ligent hosts. OSI model was developed as a standard and serves more as a teaching aid. This is because it clearly demarcates the functionality to t