1 Figure 3-2: TCP/IP Standards (Study Figure) Origins  Defense Advanced Research Projects Agency (DARPA) created the ARPANET  An internet connects multiple individual networks  Global Internet is capitalized  Internet Engineering Task Force (IETF)  Most IETF documents are requests for comments (RFCs)  Internet Official Protocol Standards: List of RFCs that are official standards

2 Figure 3-2: TCP/IP Standards (Study Figure) Hybrid TCP/IP-OSI Architecture (Figure 3-3)  Combines TCP/IP standards at layers 3-5 with  OSI standards at layers 1-2 TCP/IP Application Transport Internet OSI Subnet Access: Use OSI Standards Here Hybrid TCP/IP-OSI Application Presentation Session Application Transport NetworkInternet Data Link Physical

3 Figure 3-2: TCP/IP Standards (Study Figure) OSI Layers  Physical (Layer 1): defines electrical signaling and media between adjacent devices  Data link (Layer 2): control of a frame through a single network, across multiple switches Switched Network 1 Data Link Physical LinkFrame

4 Figure 3-2: TCP/IP Standards Internet Layer  Governs the transmission of a packet across an entire internet. Path of the packet is its route Switched Network 1 Switched Network 2 Switched Network 3 Router Route Packet

5 Figure 3-2: TCP/IP Standards (Study Figure) Frames and Packets  Frames are messages at the data link layer  Packets are messages at the internet layer  Packets are carried (encapsulated) in frames  There is only a single packet that is delivered from source to destination host  This packet is carried in a separate frame in each network

6 Figure 3-2: TCP/IP Standards (Study Figure) Internet and Transport Layers  Purposes Internet layer governs hop-by-hop transmission between routers to achieve end-to-end delivery Transport layer is end-to-end (host-to-host) protocol involving only the two hosts  Internet Protocol (IP) IP at the internet layer is unreliable—does not correct errors in each hop between routers This is good: reduces the work each router along the route must do

7 Figure 3-2: TCP/IP Standards (Study Figure) Transport Layer Standards  Transmission Control Protocol (TCP) Reliable and connection-oriented service at the transport layer Corrects errors  User Datagram Protocol (UDP) Unreliable and connectionless service at the transport layer Lightweight protocol good when catching errors is not important

8 Figure 3-7: Internet and Transport Layers Transport Layer End-to-End (Host-to-Host) TCP is Connection-Oriented, Reliable UDP is Connectionless Unreliable Client PC Server Internet Layer (Usually IP) Hop-by-Hop (Host-Router or Router-Router) Connectionless, Unreliable Router 1Router 2Router 3

9 Figure 3-2: TCP/IP Standards (Study Figure) Application Layer  To govern communication between application programs, which may be written by different vendors  Document transfer versus document format standards HTTP / HTML for WWW service SMTP / RFC 822 (or RFC 2822) in  Many application standards exist because there are many applications

10 Figure 3-8: HTML and HTTP at the Application Layer Webserver Hypertext Markup Language (HTML) Document or Other File (jpeg, etc.) Client PC with Browser Hypertext Transfer Protocol (HTTP) Requests and Responses

11 Figure 3-3: TCP/IP and OSI Architectures: Recap TCP/IP Application Transport Internet OSI Subnet Access: Use OSI Standards Here Hybrid TCP/IP-OSI Application Presentation Session Application Transport NetworkInternet Data Link Physical Note: The Hybrid TCP/IP-OSI Architecture is used on the Internet and dominates internal corporate networks.