opics Covered Connection-oriented versus connectionless TCP is connection-oriented Http is connectionless Hybrid TCP/P-OSI Architecture OSI is nearly 100% dominant at Layers 1 and 2 TCP/P is 70% to 80 dominant at layers 3 and 4 Situation at layer 5 is complex 16
16 Topics Covered • Connection-oriented versus connectionless – TCP is connection-oriented – HTTP is connectionless • Hybrid TCP/IP-OSI Architecture – OSI is nearly 100% dominant at Layers 1 and 2 – TCP/IP is 70% to 80% dominant at Layers 3 and 4 – Situation at Layer 5 is complex
Topics Covered Hybrid TCP/P-OSI Standards Architecture 5. Application layer(application-to-application) 4. Transport layer(host-to-host) 3. Internet layer(across an internet) 2. Data link layer (across a switched network) 1. Physical layer(between adjacent devices)
17 Topics Covered • Hybrid TCP/IP-OSI Standards Architecture – 5. Application layer (application-to-application) – 4. Transport layer (host-to-host) – 3. Internet layer (across an internet) – 2. Data link layer (across a switched network) – 1. Physical layer (between adjacent devices)
Topics Covered Ethernet Source and destination addresses are 48 bits long Switches forward packets by destination addresses Data field encapsulates an ip packet Unreliable: if detects an error, drops the frame Internet Protocol (IP) 32-bit addresses Show 32 bits on each line Unreliable: checks headers for errors but discards 18
18 Topics Covered • Ethernet – Source and destination addresses are 48 bits long – Switches forward packets by destination addresses – Data field encapsulates an IP packet – Unreliable: if detects an error, drops the frame • Internet Protocol (IP) – 32-bit addresses – Show 32 bits on each line – Unreliable: checks headers for errors but discards
Topics Covered Vertical Communication on the source host Layer process creates message and then sends the message to the next-lower layer Next-lower layer encapsulates the message in its own message This continues until the final frame at the data link layer Vertical communication on the destination host Decapsulation and passing up 19
19 Topics Covered • Vertical Communication on the Source Host – Layer process creates message and then sends the message to the next-lower layer – Next-lower layer encapsulates the message in its own message – This continues until the final frame at the data link layer • Vertical Communication on the Destination Host – Decapsulation and passing up
Topics Covered Not All devices Have all layers Hosts have all five Routers have only the lowest three Switches have only the lowest two 20
20 Topics Covered • Not All Devices Have All Layers – Hosts have all five – Routers have only the lowest three – Switches have only the lowest two