Path Maximum Transfer Unit - Novell NETWARE 6-DOCUMENTATION Manual

Figure 4 Basic frame of an IP Datagram
Header
Information

Path Maximum Transfer Unit

IP Datagram Header
Destination
Source IP
IP Address
Address
The IP address for a node is a logical address and is independent of any
particular hardware or network topology. It has the same form, regardless of
the media type. The IP address (version 4) is a 4-byte (32-bit) numeric value
that identifies both a network and a local host or node (computer or other
device) on that network. The 4-byte IP address is usually represented in dotted
decimal notation. Each byte is represented by a decimal number, and periods
separate the bytes, for example, 129.47.6.17.
The Data-Link layer transmits IP packets in the data section of its physical
frame. Because IP supports a 64-KB packet length, an IP datagram might not
fit in a data-link frame. Also, in traveling to its destination, a datagram can
traverse many different media with different physical frame lengths. An IP
router might have to forward a packet across media in which the inbound and
outbound frame lengths differ.
To handle these potential problems with packet transmission, IP specifies a
method for breaking datagrams into fragments. The fragments are
reassembled when they arrive at the final destination. Reassembling
fragments reconstructs the entire IP datagram.
The maximum transfer unit (MTU) is the largest amount of data that can be
transferred across a given physical network. For local area networks, such as
Ethernet, the MTU is determined by the network hardware. For wide area
networks that use serial lines to interconnect packet switches, the MTU is
determined by software.
The Path MTU is the smallest of all MTUs, for the hops along a path from the
source host to the destination host. The Path MTU governs the size of the
IP Datagram Data
Options
Data
Understanding
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