Operation Manual

AT-RG213 Residential VoIP Gateway - SIP Software Reference Manual
SIP Software Release 6-0-0
J613-M0524-00
20
Figure 4. IP packet or datagram
ver IHL type of service total length
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
identification flags
fragment offset
time to live protocol header checksum
source IP address
destination IP address
options
padding
user data
Table 11. Functions of the fields in an IP datagram
Field Function
ver The version of the IP protocol that created the
datagram.
IHL The length of the IP header in 32-bit words (the
minimum value is 5).
Type of service The quality of service (precedence, delay,
throughput, and reliability) desired for the
datagram.
Total length The length of the datagram (both header and user
data), in octets.
Identification A 16-bit value assigned by the originator of the
datagram, used during reassembly
Flags Control bits indicating whether the datagram may
be fragmented, and if so, whether other later
fragments exist
Fragment offset The offset in the original datagram of the data
being carried in this datagram, for fragmented
datagrams
Time to live The time in seconds the datagram is allowed to
remain in the internet system