N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 6 - Internet, Intranet, Extranet, e-Commerce and Web Services                                      Slide 24 of 70 _________________                                                                                  __________

                                TCP / IP Model Mapping to OSI Model

                                                        TCP/IP Layers

_________________                                                                                  __________

The OSI and the TCP/IP are two different models for computer systems networking. The OSI model has distributed the networking functions into seven layers. The TCP/IP uses a four layer model. The four layer model provides the same functionality as the OSI model. The TCP/IP model has Application, Transport (host-to-host), Internet and Internet Interface layers.

Application Layer - Applications that provide network support reside in this layer. This layer maps to the session, Presentation and Application layers of the OSI model. The protocols (FTP, NFS and HTTP) and utilities (SMTP and SNMP) function at this layer.

Transport Layer - This layer provides host-to-host communications for guaranteed and non-guaranteed data delivery services. TCP and UDP function at this layer.

Internet Layer - This layer is similar to the Network Layer of the OSI model which provides routing and addressing services. IP, Address Resolution Protocol (ARP) and Internet Control Message Protocol (ICMP) protocols provide the Internet Layer services.

Network Interface Layer - This layer maps to the Physical Layer and the Data Link Layer of the OSI model.