Visor Neo - 468x60


INTERNET PROTOCOL (IP) 
(see RFC 791)


The Internet Protocol (IP) provides a frame for encapsulating other protocols like TCP 
and UDP. The IP header informs the recipient among other things of: the destination and 
source addresses of the packet, number of octets in the packet, whether the packet can be 
fragmented or not, how many hops can the packet traverse, the protocol that the packet 
carries, etc. The IP version currently utilizied is 4.
IP HEADER FORMAT

OCTET 1			Version (4 bit)+IHL (4 bit)		(VER, IHL)
OCTET 2			Type of service				(TOS)
OCTET 3,4		Total Length				(TOL)
OCTET 5,6 		Identification				(ID)
OCTET 7,8		Flags (3 bit)+Fragment Offset (13 bit)	(FLG, FRO)
OCTET 9			Time to Live				(TTL)
OCTET 10		Protocol				(PRO)
OCTET 11,12 		Header Checksum				(IP_SUM)
OCTET 13,14,15,16 	Source Address				(SRC)
OCTET 17,18,19,20	Destination Address			(DEST)
OCTET 21,22,23		Options					(OPT)
OCTET 24		Padding
OCTET 25, 26 … 		Data

In the example shown the IP packet is encapsulated in a PPP frame including the 
flag sequence (7E), address (FF 03), protocol (00 21) and FCS (0B 81). In turn, the IP 
packet encapsulates a UDP message. 

Example:

7E FF 03 00 21 45 00 00 40 00 01 00 00 3C 11 E0 31 CE D9 8F 1F C7 B6 78 CB 04 63 00 
35 00 2C AB DA 00 01 01 00 00 01 00 00 00 00 00 00 04 70 6F 70 64 02 69 78 06 6E 65 
74 63 6F 6D 03 63 6F 6D 00 00 01 00 01 0B 81 7E

Start		7E
Address		FF 03
SEP		00 21
IP Header	45 00 00 40 00 01 00 00 3C 11 E0 31 CE D9 8F 1F C7 B6 78 CB 
Data		04 89 00 35 00 2C AB B4 00 01 01 00 00 01 00 00 00 00 00 00 04 70 6F 
		70 64 02 69 78 06 6E 65 74 63 6F 6D 03 63 6F 6D 00 00 01 00 01
FCS		0B 81
Stop		7E

IP Header
VER=4 IHL=5 TOS=0 TOL=64 ID=1 FLG=00 FRO=00 TTL=60 PRO=17 IP_SUM=E031 
SRC=206.217.143.31. DEST=199.182.120.203. OPT=00000000
Click Next for IP Checksum calculation code.

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