IT 210: Web-based IT Fall 2012 IP Address Details & HTTP Protocol

IP Address Details

Refresher…  What function do IP Addresses serve?

IP Addresses  Composed of 2 parts: network ID (prefix assigned by ISPs) and host ID (suffix assigned by local sysadmin)  IPv4 addresses consist of 4 octets  How much of the IP address is used as a network ID?

Assigning IP Addresses

Classful IP Address Assignment

IP address classes (32 bits = v4) ClassLeftmos t bits Start address Finish address Net bitsHost bits A0xxx (16M) B10xx (65K) C110x (256) D multicast E experimental

Many exceptions  = loopback = “home” or localhost  Private addresses (see table) ClassPrivate start addressPrivate end address A B C

Script Kiddies

CIDR (Classless Inter-Domain Routing)  The “prefix” (ironically shown after the IP address) indicates how many bits in the Network ID. E.g., /16 CIDR & # of Hosts /13 524,288 /14 262,144 /15 131,072 /16 65,536 /17 32,768 /18 16,384 /19 8,192 /20 4,096 /21 2,048 /22 1,024 / / / /26 64 /27 32

Dynamic vs Static IP Addresses  Static vs Dynamic

IP4 vs IP6  In Jan 2011 we ran out of IPv4 addresses.  IP4: 32-bit address 4.2 billion addresses available (2 32 )  IP6: 128-bit address 3.4 x addresses available (2 128 ) 2001:0f68:0000:0000:0000:0000:1986:69af which condenses to 2001:f68::1986:69af

Aside: What is an RFC?  RFC “Request for Comment” Modern RFCs are NOT requesting comments (Draft docs are used for that) Standards, informational, and other stuff Published by IETF  IETF = Internet Engineering Task Force

References  RFC An Architecture for IP Address Allocation with CIDR RFC 1518  RFC Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy RFC 1519  RFC IP Version 6 Addressing Architecture RFC 2373

Questions…  True or False: The classless inter-domain routing (CIDR) system helps assure that fewer IP addresses are “wasted”.  True or False: When I switch networks my IP address will also need to change.  How many unique IP addresses are there in IP4 and IP6?

Open up command-line…  Type in ipconfig  Now try ipconfig /all  Compare the IP address to what you find here:  Try this again at home. Will it be different?

HTTP

See online tutorial  ogramming/webprogramming/HTTP_Basic s.html ogramming/webprogramming/HTTP_Basic s.html