4

8

16

32 bits

Ver

IHL

Type of Service/
DSCP & ECN

total length

Identification

 Flags |      Fragment offset

Time to Live

Protocol

Header checksum

Source address

Destination address

Options + Padding

Data

Vers

Version - Kennzeichnet die verwendete Version des IP-Protokolls, "4" für V4

IHL

Internet Header Length - Länge des IP-Headers in Einheiten von 32bit (mind. 5)

Type of Service























Differentiated Service

alte Interpretation
Festlegung einer Dienstgüte - z.B. Priorität, Verzögerungsrate, Durchsatz, Zuverlässigkeit

Prec	0	Routine
	1	Priority
	2	Immediate
	3	Flash
	4	Flash override
	5	CRITIC/ECP
	6	Internetwork control
	7	Network control
D	Low delay
T	High throughput
R	High reliability
M	Minimize monetary cost

neue Interpretation
Das DSCP Feld nach RFC2474 ersetzt bei IPv4 das Type Of Sevice Feld (RFC3168)

ECN-bits	xx
ECN-Capable Transport (ECT)
Congestion Experienced (CE)
Class Selector PHB (Per Hop Behavior)	xxx000
Assured Forwarding PHB (AF PHB) / Expedited Forwarding PHB (EF PHB)	all other

total length

Gesamtlänge (Header + Daten) des IP-Datagramms

Identification

für Reassemblierung von Fragmenten

Flags

Fragment offset

Position des aktuellen Fragments im Datagramm in Einheiten von 64bit

Time to Live

Lebensdauer bei Abarbeitung durch Router(Verwerfen des Datagramms bei 0)

Protocol

Transportprotokoll (TCP,UDP,ICMP,...)

Header checksum

Checksumme des Headers, Neuberechnung durch jeden Router (ohne Daten)

Source address

Absender IP-Adresse

Destination address

Empfänger IP-Adresse

Options + Padding

optionale Parameter (0..40 Bytes)

C	Copy
Class	0	Control
	1	"Reserved"
	2	Debugging ans measurement
	3	"Reserved"
Option	0	End of Option list
	1	NOP
	2	Security
	3	Loose Source Route
	4	Time stamp	[RFC781],[RFC791]
	5	Extended Security	[RFC1108]
	6	Commercial Security
	7	Record Route	[RFC791]
	8	Strem Identifier	[RFC791],[RFC1122]
	9	Strct Source Route	[RFC791]
	10	Experimental Measurement
	11	MTU Probe	[RFC1063]
	12	MTU Reply	[RFC1063]
	13	Experimental Flow Control
	14	Experimental Access Control
	15
	16	IMI Traffic Descriptor
	17	Extended Internet Proto
	18	Traceroute	[RFC1393]
	19	Adress Extension	[RFC1475]
	20	Router Alert	[RFC2113]
	21	Selective Directed Broadcast Mode	[RFC1770]
	22	NSAP Addresses
	23	Dynamic Packet State
	24	Upstream Multicast Packet
	...

plus Füllbytes auf 32bit-Grenze

4

8

16

24

32 bits

Ver

Priority

Flow label

Payload length

Next header

Hop limit

Source address
(128 bits)

Destination address
(128 bits)