05_Network Layer_3

00:00 - CONTENT of this CHAPTER 00:08 - Some Meta Remarks about IP – especially v4 01:21 - Overview of IP – it started with v4 02:41 - CONTENT of this CHAPTER 02:48 - IPv4 packet format 03:21 - Version number tells what other fields to expect, e.g., “4” for IPv4, “6” for IPv6 04:08 - The header length denotes the number of 32-bits word in the header, typically set to 5 (20 bytes header) 04:44 - The ToS allows different packets to be treated differently, e.g., low delay for voice, high bandwidth for video 05:42 - Differentiated Services 08:47 - Differentiated Services Examples 10:44 - Differentiated Services Examples 13:00 - The total length denotes the # of bytes in the entire packet 13:16 - The next three fields are used when packets are fragmented 14:19 - Why do we need fragmentation? 15:46 - Every link on the Internet has a Maximum Transmission Unit (MTU) 17:23 - Assume Alice is sending 4000B packets to Bob, who is connected to a 1500B MTU link 17:40 - Because packet is larger than MTU to Bob, upstream router of Bob will fragment the packet 18:02 - Packet header introduces overhead 18:35 - The Identification header uniquely identifies the fragments of a particular packet 19:07 - Flags are used to tell whether there are more fragments coming or not 20:11 - The fragment offset is used to put back the fragments in the right order in case of reordering 20:25 - Example of fragment offset 22:02 - The TTL is used to limit packet travel time 24:01 - TTL is decremented by 1 at each router, the packet is discarded if TTL reaches 0 25:12 - The protocol field identifies the higher-level protocol carried in the packet, e.g., “6” for TCP, “17” for UDP 25:46 - The checksum is the sum of all the 16 bits words in the header 26:45 - The source and destination IP addresses identify the source and destination hosts 27:01 - Options were initially put to provide additional flexibility. For security reasons, there are often deactivated. 27:51 - Support of IPv4 Header Options in the Real-World 29:52 - Questions & Tasks