Bootstrapping with bootp and dhcp
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Bootstrapping with bootp and dhcp

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The process of starting a computer system is known as bootstrapping.

The process of starting a computer system is known as bootstrapping.

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Bootstrapping with bootp and dhcp Bootstrapping with bootp and dhcp Presentation Transcript

  • Presented By===========Ashish MalikM.Tech - Information Security & Computer Forensics (SRM University)
  •  The process of starting a computer system is known as bootstrapping. The sequence begins with code in ROM  It loads an image in RAM Two approaches to obtain an image :  Embedded System ▪ ROM code use n/w support to locate & download image.  Conventional Computer ▪ ROM code loads image from well-known place on disk.
  •  Loaded image is not configured according to the specific physical hardware. It does not contain any networking details. Early implementation of TCP/IP provided separate mechanism to obtain configuration information e.g. RARP to obtain IP address. When subnet masks were introduced, ICMP address mask message were added to obtain a subnet mask. View slide
  •  Advantage  Flexibility  Computer decides which item to obtain from local disk and which to obtain over the n/w. Disadvantage  Network traffic and delay  Computer issues request messages to server. Each response returns a small value (IP). Networks enforce min. packet size, so most of the space in each packet is wasted. View slide
  •  It was invented to supply more than one item of configuration information in a single step. BOOTP server provide several pieces of information at once like :  Computers IP address  Server’s name and IP address  IP address of a default router BOOTP uses IP to send request and receive response.
  •  How BOOTP uses Unconfigured IP ? It’s design allow IP to broadcast an IP datagram request before all values have been configured. Destination address used : all 1’s Source address used : all 0’s BOOTP responds either via broadcast message or via MAC address.
  •  BOOTP uses UDP so messages can be delayed, lost or duplicated. BOOTP requires that UDP use checksums. To handle datagram loss, BOOTP uses technique of timeout & retransmission.
  •  BOOTP uses a two-step bootstrap procedure: ▪ It only provides client with the information needed to obtain an image. ▪ Client then uses TFTP to obtain the image.  BOOTP was designed for a static environment.  With advent of networking and portable PC’s, BOOTP does not adapt to such situations as info. can not be exchanged quickly.  Hence we needed another protocol, DHCP.
  •  Dynamic Host Configuration Protocol It was devised to automate the configuration. It use plug-and-play networking to join a new network and obtain an IP address. DHCP server can be configured to have two type of addresses :  Permanent addresses ▪ Assigned to server computers.  Pool of addresses ▪ These are to be allocated on demand.
  •  Addresses assigned on demand are not permanent. DHCP issues a lease on the address for a finite period of time. If lease expires, computer must renegotiate with the DHCP server. If an event cause all computers to restart at same time, DHCP uses the same technique as BOOTP to avoid flooding with requests.  i.e. waiting for a random amount of time.
  •  This protocol has two steps :  Broadcast DHCP discover message  Send request to server that responded To avoid repeating above steps, DHCP uses caching.
  • Thank You