02-18-2011
Hi
An IPv4 address contains 4 octets i.e. 32 bits. ip addresses are divided into 4 classes depending upon how many bits in 32 bits represent the network address and how many bits represent the host address.
for instance the class A ip address has the first 8 bits represent the network address and rest 24 bits represent the host address.
A network mask is the one which helps you finding which part in 32 bits represents the network address. Say for class A the network mask is 255.0.0.0
So in general a class A ip address can be represented as 1.2.3.4 255.0.0.0
There is another concept called as sub-netting which makes use of some bits in the host part for network address. Sub-netting allows you to create multiple logical networks inside classes of networks.
for example we can create an IP subnet for class A by using 3 bits of 24 host bits for network address. In this case the first 11 bits of 32 represent the network address and the reset 21 bits represent the host address.
In such cases the class A address can be represented as 1.2.3.4 255.224.0.0
The above representation is called as address/mask representation.. There is another representation know as CIDR (Classless inter-domain routing) which represents the ip address irrespective of class, but represents the number of bits used for network address.
In the CIDR representation the ip address in the above example is represented as 1.2.3.4/11 since 11 bits are used as mask.
so, in the representation of ip address 193.32.156.0/24 and 169.183.0.0/16, 24 and 16 represent the mask bits...so the above two addresses are class c and class b respectively.
Thanks,
Chaitanya.
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LEARN ABOUT SUSE
mail::address
Mail::Address(3) User Contributed Perl Documentation Mail::Address(3)
NAME
Mail::Address - Parse mail addresses
SYNOPSIS
use Mail::Address;
my @addrs = Mail::Address->parse($line);
foreach $addr (@addrs) {
print $addr->format,"
";
}
DESCRIPTION
"Mail::Address" extracts and manipulates email addresses from a message header. It cannot be used to extract addresses from some random
text. You can use this module to create RFC822 compliant fields.
Although "Mail::Address" is a very popular subject for books, and is used in many applications, it does a very poor job on the more complex
message fields. It does only handle simple address formats (which covers about 95% of what can be found). Problems are with
o no support for address groups, even not with the semi-colon as separator between addresses;
o limitted support for escapes in phrases and comments. There are cases where it can get wrong; and
o you have to take care of most escaping when you create an address yourself: "Mail::Address" does not do that for you.
Often requests are made to the maintainers of this code improve this situation, but this is not a good idea, where it will break zillions
of existing applications. If you wish for a fully RFC2822 compliant implementation you may take a look at Mail::Message::Field::Full, part
of MailBox.
example:
my $s = Mail::Message::Field::Full->parse($header);
# ref $s isa Mail::Message::Field::Addresses;
my @g = $s->groups; # all groups, at least one
# ref $g[0] isa Mail::Message::Field::AddrGroup;
my $ga = $g[0]->addresses; # group addresses
my @a = $s->addresses; # all addresses
# ref $a[0] isa Mail::Message::Field::Address;
METHODS
Constructors
Mail::Address->new(PHRASE, ADDRESS, [ COMMENT ])
Create a new "Mail::Address" object which represents an address with the elements given. In a message these 3 elements would be seen
like:
PHRASE <ADDRESS> (COMMENT)
ADDRESS (COMMENT)
example:
Mail::Address->new("Perl5 Porters", "perl5-porters@africa.nicoh.com");
$obj->parse(LINE)
Parse the given line a return a list of extracted "Mail::Address" objects. The line would normally be one taken from a To,Cc or Bcc
line in a message
example:
my @addr = Mail::Address->parse($line);
Accessors
$obj->address
Return the address part of the object.
$obj->comment
Return the comment part of the object
$obj->format([ADDRESSes])
Return a string representing the address in a suitable form to be placed on a "To", "Cc", or "Bcc" line of a message. This method is
called on the first ADDRESS to be used; other specified ADDRESSes will be appended, separated with commas.
$obj->phrase
Return the phrase part of the object.
Smart accessors
$obj->host
Return the address excluding the user id and '@'
$obj->name
Using the information contained within the object attempt to identify what the person or groups name is.
$obj->user
Return the address excluding the '@' and the mail domain
SEE ALSO
This module is part of the MailTools distribution, http://perl.overmeer.net/mailtools/.
AUTHORS
The MailTools bundle was developed by Graham Barr. Later, Mark Overmeer took over maintenance without commitment to further development.
Mail::Cap by Gisle Aas <aas@oslonett.no>. Mail::Field::AddrList by Peter Orbaek <poe@cit.dk>. Mail::Mailer and Mail::Send by Tim Bunce
<Tim.Bunce@ig.co.uk>. For other contributors see ChangeLog.
LICENSE
Copyrights 1995-2000 Graham Barr <gbarr@pobox.com> and 2001-2007 Mark Overmeer <perl@overmeer.net>.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See
http://www.perl.com/perl/misc/Artistic.html
perl v5.12.1 2010-01-26 Mail::Address(3)