![]() A port number is 16 bits giving a decimal range of 0 to 65535. This format is typically only used where a service is available on a non-standard port number, for instance, many web configuration systems, such as Samba swat, will use a non-standard port to avoid clashing with the standard web (HTTP) port number of 80. The : (colon) indicates the number following is a Port Number - in the above case 369. You will occasionally see IPv4 addresses written like this: In a CIDR world it is determined exclusively by the NetMask. The boundary between the Network address part and the Host Address part was determined by the IP Address class and the NetMask or the SubnetMask. "dotted decimal" simply converts the 8 bit value for each byte (octet) to its decimal value (which is always in the range 0 to 255) and separates each value with a dot to make it more readable resulting in, for example, 192.168.2.5.Įach IP address has two components a network address and a host address (or id). It's a bit tough to remember numbers of this size so the conventional way of writing an IP address is in "dotted decimal" format, for example, 192.168.0.27.Ī "dotted decimal" IP address is constructed as follows:Ī 32 bit address contains 4 x 8 bit bytes (or octets)Įach 8 bit byte (octet) may represent 256 ( 0 - 255) decimal values. Our own preference is for Power of 2 notation - but that's another story.Īn IP v4 address is a 32 bit value which allows 4,294,967,296 unique addresses. Use of network order is necessary since the internal (machine) representation of data can vary enormously (all that big-endian, little-endian nonsense) but when data is stuffed onto a network it must be in a consistent order that can be used by any system, irrespective of its internal representation, that wants to use the data. Bits also tend to come off the network in the same order they went on. ![]() ![]() The IETF's rationale for this standard is that it also represents unambiguously what is called network order, that is, bit 0 goes onto a network first, bit 1 second and so on. We have bowed to the inevitable and this document uses the Left to right base 0 (IETF) standard since, because of the Internet, it is widely used and, hopefully, equally widely understood. Memory contentsĪlways check what convention is used on any specification. The following are all valid, and used, bit numbering conventions for describing an 8 bit byte (an octet). IP Prefix (Slash) notation - 192.168.2/24īit numbering can be very confusing with various standard bodies adopting different conventions.Further, the adoption of IPv6 by the wireless world is probably the only way to supply the staggering number of mobile devices the world seems capable of consuming. Indeed, it is no exaggeration to say that a rising tide of panic is being fostered in an effort to increase the pace of IPv6 migration. While the immediate pressure for new IP addresses was hugely reduced in the mid-late 90s by CIDR, NAT and other initiatives, the increasingly dire warnings from the Regional Internet Registries (RIRs) of IPv4 address depletion are placing renewed emphasis on IPv6 deployment. IPv4 is being progessively replaced with IPv6 (version 6 of the IP protocol) which uses a 128 bit address and greatly extends the address range of the Internet. See also IPv4 headers, TCP, UDP and IPv4 ICMP messages for the insatiably curious. This type of address is almost universally written as IPv4. Most of this note is concerned with IP addresses used in version 4 of the IP protocol which uses a 32 bit IP address, such as, 192.168.0.15. If you don't like this stuff stick to origami or try this memory jogger - Binary, Decimal and Hexadecimal To understand this stuff you need to be be comfortable with decimal, hexadecimal and binary notation. Tech Stuff - IPv4 Classes, Subnets, Netmasks, CIDR and NAT
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |