Experiments

packet

2 min read

Packet

  • aka Datagrams, Segments, Data blocks, Cells or Frames
  • A packet is the most basic unit used in data delivery over a network.
  • Every data packet generally contains
    • Header
      • source address
      • destination address
      • payload length
      • Time to live
      • Protocol
    • Payload
  • Each packet is only few KBs
  • Hundreds of Thousands of packets in a single data stream
  • Size of packet is less:
    • retransmit of packet becomes easier if it gets lost

TTL

  • Time to Live
  • Is part of each final packet
  • Defines the number of hops allowed from source to destination before it’s considered lost
  • Each packet in a data stream do not take the same route to reach the destination
  • Without TTL data could get lost in an endless loop of routers or go missing and not be resent.

PDU

  • Protocol Data Unit
  • It is a generic term. It is used to describe the form of a data packet at any layer in the TCP/IP model stack.
  • Going down each Layer in TCP/IP stack, encapsulates header information at that layer
TCP/IP LayerPDU Name
ApplicationData
TransportSegment
InternetPacket
Network InterfaceFrame

Tracing packets

  • use tracert in Windows
  • use traceroute in MacOS
$traceroute google.com
 1  10.119.11.1 (10.119.11.1)  119.591 ms  67.853 ms  38.443 ms
 2  * * *
 3  108.170.238.39 (108.170.238.39)  76.695 ms  74.358 ms
    172.253.50.221 (172.253.50.221)  53.299 ms
 4  192.178.86.76 (192.178.86.76)  52.332 ms
    192.178.83.168 (192.178.83.168)  102.789 ms
    192.178.83.178 (192.178.83.178)  54.164 ms
 5  142.251.246.203 (142.251.246.203)  112.355 ms
    142.251.246.209 (142.251.246.209)  84.064 ms
    142.251.246.205 (142.251.246.205)  83.719 ms
 6  * * *
 7  * * *
 8  142.251.250.168 (142.251.250.168)  217.252 ms *  190.281 ms
 9  * * 142.250.58.52 (142.250.58.52)  291.500 ms
10  142.250.213.71 (142.250.213.71)  307.008 ms  307.119 ms
    142.250.213.61 (142.250.213.61)  343.171 ms
11  216.239.57.137 (216.239.57.137)  326.038 ms
    142.250.213.63 (142.250.213.63)  364.106 ms
    216.239.57.137 (216.239.57.137)  320.075 ms
12  * * 72.14.233.104 (72.14.233.104)  531.002 ms
13  * 172.253.71.165 (172.253.71.165)  409.711 ms *
14  142.251.242.237 (142.251.242.237)  444.975 ms
    142.251.242.235 (142.251.242.235)  876.852 ms
    142.251.248.253 (142.251.248.253)  451.631 ms
15  192.178.108.149 (192.178.108.149)  447.153 ms
    192.178.108.147 (192.178.108.147)  465.491 ms
    142.251.242.237 (142.251.242.237)  453.483 ms
16  142.251.224.97 (142.251.224.97)  457.116 ms
    192.178.108.181 (192.178.108.181)  450.913 ms  451.797 ms
17  142.251.224.97 (142.251.224.97)  486.271 ms
    142.251.228.197 (142.251.228.197)  478.356 ms
    142.251.224.97 (142.251.224.97)  452.929 ms
18  tztlva-ab-in-f14.1e100.net (142.250.75.78)  478.560 ms  441.572 ms  476.395 ms