CCNA Cisco Certified Network Associate Study Guide - FTP Server

Flags Specifies whether fragmentation should occur.
TCP/IP and the DoD Model 119
Frag offset Provides fragmentation and reassembly if the packet is too
large to put in a frame. It also allows different Maximum Transmission
Units (MTUs) on the Internet.
TTL Time to Live is set into a packet when it is originally generated. It
gives it a time to live. If it doesn’t get to where it wants to go before the
TTL expires, boom—it’s gone. This stops IP packets from continuously
circling the network looking for a home.
Protocol Port of upper-layer protocol (TCP is port 6 or UDP is
port 17 (hex)).
Header checksum Cyclic Redundancy Check on header only.
Source IP address 32-bit IP address of sending station.
Destination IP address 32-bit IP address of the station this packet is destined
for.
IP option Used for network testing, debugging, security, and more.
Data Upper-layer data.
Here’s a snapshot of an IP packet caught on a network analyzer. Notice
that all the information discussed above appears here:
IP Header - Internet Protocol Datagram
Version: 4
Header Length: 5
Precedence: 0
Type of Service: %000
Unused: %00
Total Length: 187
Identifier: 22486
Fragmentation Flags: %010 Do Not Fragment
Fragment Offset: 0
Time To Live: 60
IP Type: 0x06 TCP
Header Checksum: 0xd031
Source IP Address: 10.7.1.30
Dest. IP Address: 10.7.1.10
No Internet Datagram Options