Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

90 CHAPTER 6 TCP/IP and Routing
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IP supports the ability to send to a group through multicasting.
IP provides the network layer addressing and functions for the TCP/IP
stack.
Information is transported in IP packets, in which the header remains
consistent in terms of size and fields.
IP Version 4
IP is responsible for addressing and delivery by providing a logical address
scheme. The original version of IP, referred to as IP version 4 (IPv4), consists
of 32 bits spread over four 8-bit octets, expressed in dotted decimal format. For
example, a 32-bit address may look like this in binary:
00001010000010110000110000001101
To improve readability, the 32-bit IP address splits into four blocks of 8 bits
like this:
00001010 00001011 00001100 00001101
Finally, each 8-bit block is converted to decimal and the decimal values are separated
with periods or dots. The converted IPv4 address, expressed as a dotted
decimal address, is:
10.11.12.13
All information transported over IP is carried in IP packets. Some components
of a packet are as follows:
■ Version 4-bit field that identifies the version of IP (4 or 6).
■ Header length 4-bit field that indicates the length of the header, as the IPv4
header is a variable between 20 and 64 bytes.
■ Time to live (TTL) Limits the number of hops the packet is allowed to
transit. At each hop, a router decrements (reduces) this field, and when it
reaches zero, the packet is removed from the network. This prevents packets
from bouncing around a network indefinitely when there is some sort of
routing problem.
■ Protocol Indicates the next protocol (header) following the IPv4 header,
such as TCP or User Datagram Protocol (UDP)
■ Header checksum Maintains the integrity of the IPv4 header.
■ Source and destination address (32-bit addresses) Identify the source and
destination for this packet.
IP Version 6
IP version 6 (IPv6), if implemented fully in the future, will solve the address
depletion problem. IPv6 addresses are 128-bit identifiers for interfaces and
sets of interfaces, not nodes. Three general types of addresses exist within