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Networking & dns 101


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Lynx Consultants presentation to train Junior Engineers into the basics of networking

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Networking & dns 101

  1. 1. Marc  Cluet  –  Lynx  Consultants    
  2. 2. What we’ll cover?¡  Understand  how  networking  works  ¡  Understand  all  the  basic  networking  protocols  ¡  Understand  how  DNS  works  ¡  Be  more  awesome!  Lynx  Consultants  ©  2013  
  3. 3. What is a Network?¡  A  computer  network,  or  simply  a  network,  is  a  collection  of  computers  and  other  hardware  interconnected  by  communication  channels  that  allow  sharing  of  resources  and  information.[1]  Where  at  least  one  process  in  one  device  is  able  to  send/receive  data  to/from  at  least  one  process  residing  in  a  remote  device,  then  the  two  devices  are  said  to  be  in  a  network.  A  network  is  a  group  of  devices  connected  to  each  other.  Networks  may  be  classified  into  a  wide  variety  of  characteristics,  such  as  the  medium  used  to  transport  the  data,  communications  protocol  used,  scale,  topology,  benefit,  and  organizational  scope.  (gotta  love  Wikipedia)  Lynx  Consultants  ©  2013  
  4. 4. So in plain words…¡  A  network  connects  2  or  more  computers  together  §  LAN  (Local  Area  Network)  is  inside  a  known  location  (office,  home,  etc)  §  WAN  (Wide  Area  Network)  is  a    network  that  connects      two  or  more  LANs  Lynx  Consultants  ©  2013  
  5. 5. The Internet¡  Internet  is  a  network  that  connects  in  a  fault  tolerant  way  many  networks  ¡  Our  current  version  of  the  Internet  works  over  the  protocol  IPv4  with  the  new  protocol  IPv6  starting  to  have  some  presence  Lynx  Consultants  ©  2013  
  6. 6. Internet IPv4¡  The  most  common  protocol  in  Internet  is  right  now  IPv4  ¡  IPv4  has  been  the  Internet  protocol  since  1980  (RFC  760)  ¡  IPv4  uses  32  bit  addresses,  having  a  total  space  of  4,294,967,296  unique  IPs  Lynx  Consultants  ©  2013  
  7. 7. IPv4 IP address¡  An  IPv4  IP  address  is  divided  in  8  bit  chunks  (1  byte  per  number)  Lynx  Consultants  ©  2013  
  8. 8. IPv4 IP netmask¡  A  netmask  defines  what  your  local  network  is,  anything  inside  that  netmask  is  considered  local  to  you  Lynx  Consultants  ©  2013  
  9. 9. IPv4 Problems¡  IPv4  is  running  out  of  IP  addresses  (last  /8  delivered  this  year)  ¡  IPv4  is  not  secure  for  most  uses  ¡  IPv4  was  designed  in  the  70ies  so  its  up  for  a  review  Lynx  Consultants  ©  2013  
  10. 10. IPv6 saves the day!¡  IPv6  is  the  new  internet  protocol  ¡  Uses  128  bit  addresses  ¡  There’s  more  IP  addresses  in  IPv6  than  atoms  on  planet  Earth  Lynx  Consultants  ©  2013  
  11. 11. IP gateways¡  As  IP  is  the  Internet  Protocol  it  has  to  know  how  to  talk  to  other  networks  ¡  A  gateway  server  is  the  one  who  sits  in  two  networks  at  the  same  time,  relying  packets  between  those  networks  Lynx  Consultants  ©  2013  
  12. 12. So then how the Internet works?¡  Gateways  keep  relying  your  message  from  network  to  network  until  it  reaches  the  destination  ¡  The  path  to  reach  its  destination  can  change  all  the  time  Lynx  Consultants  ©  2013  
  13. 13. IP protocols¡  IP  can  run  lots  of  different  protocols  inside,  the  most  known  ones  are  §  TCP  (Transmission  Control  Protocol)  §  UDP  (User  Datagram  Protocol)  §  ICMP  (Internet  Control  Message  Protocol)  Lynx  Consultants  ©  2013  
  14. 14. IP protocol definitions¡  TCP  sends  packets  with  complete  assurance  that  they’ll  reach  their  destination  ¡  UDP  sends  packets  without  any  kind  of  assurance  that  they’ll  reach  their  destination  ¡  ICMP  sends  control  messages  auxiliary  to  the  IP  protocol  (like  ping,  traceroute,  etc)  Lynx  Consultants  ©  2013  
  15. 15. TCP Protocol¡  Keeps  track  of  all  the  packets  it  sends  (serial  num)  ¡  Destination  acknowledges  (ACK)  every  packet  received  ¡  Packets  can  arrive  in  any  order  and  they’ll  be  reordered  at  destination  Lynx  Consultants  ©  2013  
  16. 16. TCP Ports¡  TCP  can  listen  or  talk  in  several  “channels”  at  the  same  time  ¡  Ports  are  the  channels  where  TCP  (and  UDP)  talk,  there’s  a  total  of  65,536  channels  ¡  Most  common  Ports  §  80  http  §  443  https  §  25  smtp  §  110  pop3  §  143  imap  Lynx  Consultants  ©  2013  
  17. 17. UDP Protocol¡  UDP  sends  packets  as  TCP  to  ports,  but  there’s  no  guarantee  that  the  packets  will  reach  its  destination.  ¡  This  is  ideal  for  any  kind  of  protocol  that  doesn’t  need  all  its  packets  §  Video  Streaming  §  Radio  Streaming  Lynx  Consultants  ©  2013  
  18. 18. ICMP Protocol¡  ICMP  sends  auxiliary  messages  that  help  Internet  routing  ¡  Used  in  all  of  our  common  diagnostic  tools  §  PING  (icmp  echo)  §  TRACEROUTE  (icmp  route)  Lynx  Consultants  ©  2013  
  19. 19. ICMP - Ping¡  Ping  sends  a  packet  to  a  destination  and  reads  the  reply  ¡  Bases  itself  on  ICMP  echo  ¡  Can  be  filtered  by  routers  and  inbetween  policy  filters  Lynx  Consultants  ©  2013  
  20. 20. ICMP - Traceroute¡  Traceroute  sends  requests  to  every  single  hop  between  us  and  a  destination  ¡  This  is  based  on  one  special  type  of  ICMP  packet  ¡  Some  routers  can  decide  to  filter  traceroute,  in  that  case  *  will  appear  instead  of  the  TTL  Lynx  Consultants  ©  2013  
  21. 21. What is DNS?¡  The  Internet  works  with  IP  addresses  ¡  How  can  we  remember  always  that  google  is  ¡  It’s  humanly  impossible!  Lynx  Consultants  ©  2013  
  22. 22. DNS saves the day¡  DNS  is  a  service  (listens  on  UDP  port  53)  ¡  DNS  will  give  you  the  IP  address  of  any  name  you  want  ¡  It  can  give  you  more  than  one  address  for  extra  redundancy  Lynx  Consultants  ©  2013  
  23. 23. DNS Servers¡  DNS  is  also  a  security  risk,  you  don’t  want  everyone  to  know  your  full  DNS  structure  ¡  Big  companies  will  show  you  a  different  DNS  “view”  based  on  where  you  are  Lynx  Consultants  ©  2013  
  24. 24. DNS Geo Balanced¡  DNS  is  also  very  useful  to  be  able  to  send  you  to  the  nearest  point  ¡  Try  resolving  from  different  parts  of  the  world!  Lynx  Consultants  ©  2013  is  is  
  25. 25. Questions?Lynx  Consultants  ©  2013