| PPP header | IP header | Data |
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Version | IHL | TOS | Total length | ||||||||||||||||||||||||||||
| Identification | Flags | Fragment offset | |||||||||||||||||||||||||||||
| TTL | Protocol | Header checksum | |||||||||||||||||||||||||||||
| Source IP address | |||||||||||||||||||||||||||||||
| Destination IP address | |||||||||||||||||||||||||||||||
| Options (IF ANY) and padding ::: |
|||||||||||||||||||||||||||||||
| DATA ::: |
|||||||||||||||||||||||||||||||
Version. 4 bits.
Specifies the format of the IP packet header.
| Version | Description |
|---|---|
| 0 | Reserved. |
| 1 2 3 |
|
| 4 | IP, Internet Protocol. |
| 5 | ST, ST Datagram Mode. |
| 6 | SIP, Simple Internet Protocol. SIPP, Simple Internet Protocol Plus. IPv6, Internet Protocol. |
| 7 | TP/IX, The Next Internet. |
| 8 | PIP, The P Internet Protocol. |
| 9 | TUBA |
| 10 - 14 |
|
| 15 | Reserved. |
IHL, Internet Header Length. 4 bits.
Specifies the length of the IP packet header in 32 bit words. The minimum value for a
valid header is 5.
TOS, Type of Service. 8 bits.
Specifies the parameters for the type of service requested. The parameters may be utilized
by networks to define the handling of the datagram during transport. The M bit was
added to this field in RFC 1349.
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 |
|---|---|---|---|---|---|---|---|
| Precedence | D | T | R | M | 0 | ||
Precedence. 3 bits.
| Value | Description |
|---|---|
| 0 | Routine. |
| 1 | Priority. |
| 2 | Immediate. |
| 3 | Flash. |
| 4 | Flash override. |
| 5 | CRITIC/ECP. |
| 6 | Internetwork control. |
| 7 | Network control. |
D. 1 bit.
Minimize delay.
| Value | Description |
|---|---|
| 0 | Normal delay. |
| 1 | Low delay. |
T. 1 bit.
Maximize throughput.
| Value | Description |
|---|---|
| 0 | Normal throughput. |
| 1 | High throughput. |
R. 1 bit.
Maximize reliability.
| Value | Description |
|---|---|
| 0 | Normal reliability. |
| 1 | High reliability. |
M. 1 bit.
Minimize monetary cost.
| Value | Description |
|---|---|
| 0 | Normal monetary cost. |
| 1 | Minimize monetary cost. |
Total length. 16 bits.
Contains the length of the datagram.
Identification. 16 bits.
Used to identify the fragments of one datagram from those of another. The
originating protocol module of an internet datagram sets the identification
field to a value that must be unique for that source-destination pair and
protocol for the time the datagram will be active in the internet system. The
originating protocol module of a complete datagram sets the MF bit to
zero and the Fragment Offset field to zero.
Flags. 3 bits.
| 00 | 01 | 02 |
|---|---|---|
| R | DF | MF |
R, Reserved. 1 bit.
Should be set to 0.
DF, Don't fragment. 1 bit.
Controls the fragmentation of the datagram.
| Value | Description |
|---|---|
| 0 | Fragment if necessary. |
| 1 | Do not fragment. |
MF, More fragments. 1 bit.
Indicates if the datagram contains additional fragments.
| Value | Description |
|---|---|
| 0 | This is the last fragment. |
| 1 | More fragments follow this fragment. |
Fragment Offset. 13 bits.
Used to direct the reassembly of a fragmented datagram.
TTL, Time to Live. 8 bits.
A timer field used to track the lifetime of the datagram. When the TTL field is
decremented down to zero, the datagram is discarded.
Protocol. 8 bits.
This field specifies the next encapsulated protocol.
| Value | Protocol |
|---|---|
| 0 | IPv6 Hop-by-Hop Option. |
| 1 | ICMP, Internet Control Message Protocol. |
| 2 | IGMP, Internet Group Management Protocol. RGMP, Router-port Group Management Protocol. |
| 3 | GGP, Gateway to Gateway Protocol. |
| 4 | IP in IP encapsulation. |
| 5 | ST, Internet Stream Protocol. |
| 6 | TCP, Transmission Control Protocol. |
| 7 | UCL, CBT. |
| 8 | EGP, Exterior Gateway Protocol. |
| 9 | IGRP. |
| 10 | BBN RCC Monitoring. |
| 11 | NVP, Network Voice Protocol. |
| 12 | PUP. |
| 13 | ARGUS. |
| 14 | EMCON, Emission Control Protocol. |
| 15 | XNET, Cross Net Debugger. |
| 16 | Chaos. |
| 17 | UDP, User Datagram Protocol. |
| 18 | TMux, Transport Multiplexing Protocol. |
| 19 | DCN Measurement Subsystems. |
| 20 | HMP, Host Monitoring Protocol. |
| 21 | Packet Radio Measurement. |
| 22 | XEROX NS IDP. |
| 23 | Trunk-1. |
| 24 | Trunk-2. |
| 25 | Leaf-1. |
| 26 | Leaf-2. |
| 27 | RDP, Reliable Data Protocol. |
| 28 | IRTP, Internet Reliable Transaction Protocol. |
| 29 | ISO Transport Protocol Class 4. |
| 30 | NETBLT, Network Block Transfer. |
| 31 | MFE Network Services Protocol. |
| 32 | MERIT Internodal Protocol. |
| 33 | Sequential Exchange Protocol. |
| 34 | Third Party Connect Protocol. |
| 35 | IDPR, Inter-Domain Policy Routing Protocol. |
| 36 | XTP, Xpress Transfer Protocol. |
| 37 | Datagram Delivery Protocol. |
| 38 | IDPR, Control Message Transport Protocol. |
| 39 | TP++ Transport Protocol. |
| 40 | IL Transport Protocol. |
| 41 | IPv6 over IPv4. |
| 42 | SDRP, Source Demand Routing Protocol. |
| 43 | IPv6 Routing header. |
| 44 | IPv6 Fragment header. |
| 45 | IDRP, Inter-Domain Routing Protocol. |
| 46 | RSVP, Reservation Protocol. |
| 47 | GRE, General Routing Encapsulation. |
| 48 | MHRP, Mobile Host Routing Protocol. |
| 49 | BNA. |
| 50 | ESP, Encapsulating Security Payload. |
| 51 | AH, Authentication Header. |
| 52 | Integrated Net Layer Security TUBA |
| 53 | IP with Encryption. |
| 54 | NARP, NBMA Address Resolution Protocol. |
| 55 | Minimal Encapsulation Protocol. |
| 56 | TLSP, Transport Layer Security Protocol using Kryptonet key management. |
| 57 | SKIP. |
| 58 | ICMPv6, Internet Control Message Protocol for
IPv6. MLD, Multicast Listener Discovery. |
| 59 | IPv6 No Next Header. |
| 60 | Destination Options for IPv6. |
| 61 | Any host internal protocol. |
| 62 | CFTP. |
| 63 | Any local network. |
| 64 | SATNET and Backroom EXPAK. |
| 65 | Kryptolan. |
| 66 | MIT Remote Virtual Disk Protocol. |
| 67 | Internet Pluribus Packet Core. |
| 68 | Any distributed file system. |
| 69 | SATNET Monitoring. |
| 70 | VISA Protocol. |
| 71 | Internet Packet Core Utility. |
| 72 | Computer Protocol Network Executive. |
| 73 | Computer Protocol Heart Beat. |
| 74 | Wang Span Network. |
| 75 | Packet Video Protocol. |
| 76 | Backroom SATNET Monitoring. |
| 77 | SUN ND PROTOCOL-Temporary. |
| 78 | WIDEBAND Monitoring. |
| 79 | WIDEBAND EXPAK. |
| 80 | ISO Internet Protocol. |
| 81 | VMTP, Versatile Message Transaction Protocol. |
| 82 | SECURE-VMTP |
| 83 | VINES. |
| 84 | TTP. |
| 85 | NSFNET-IGP. |
| 86 | Dissimilar Gateway Protocol. |
| 87 | TCF. |
| 88 | EIGRP. |
| 89 | OSPF, Open Shortest Path First Routing Protocol. MOSPF, Multicast Open Shortest Path First. |
| 90 | Sprite RPC Protocol. |
| 91 | Locus Address Resolution Protocol. |
| 92 | MTP, Multicast Transport Protocol. |
| 93 | AX.25. |
| 94 | IP-within-IP Encapsulation Protocol. |
| 95 | Mobile Internetworking Control Protocol. |
| 96 | Semaphore Communications Sec. Pro. |
| 97 | Ethernet-within-IP Encapsulation. |
| 98 | Encapsulation Header. |
| 99 | Any private encryption scheme. |
| 100 | GMTP. |
| 101 | IFMP, Ipsilon Flow Management Protocol. |
| 102 | PNNI over IP. |
| 103 | PIM, Protocol Independent Multicast. |
| 104 | ARIS. |
| 105 | SCPS. |
| 106 | QNX. |
| 107 | Active Networks. |
| 108 | IPPCP, IP Payload Compression Protocol. |
| 109 | SNP, Sitara Networks Protocol. |
| 110 | Compaq Peer Protocol. |
| 111 | IPX in IP. |
| 112 | VRRP, Virtual Router Redundancy Protocol. |
| 113 | PGM, Pragmatic General Multicast. |
| 114 | any 0-hop protocol. |
| 115 | L2TP, Level 2 Tunneling Protocol. |
| 116 | DDX, D-II Data Exchange. |
| 117 | IATP, Interactive Agent Transfer Protocol. |
| 118 | ST, Schedule Transfer. |
| 119 | SRP, SpectraLink Radio Protocol. |
| 120 | UTI. |
| 121 | SMP, Simple Message Protocol. |
| 122 | SM. |
| 123 | PTP, Performance Transparency Protocol. |
| 124 | ISIS over IPv4. |
| 125 | FIRE. |
| 126 | CRTP, Combat Radio Transport Protocol. |
| 127 | CRUDP, Combat Radio User Datagram. |
| 128 | SSCOPMCE. |
| 129 | IPLT. |
| 130 | SPS, Secure Packet Shield. |
| 131 | PIPE, Private IP Encapsulation within IP. |
| 132 | SCTP, Stream Control Transmission Protocol. |
| 133 | Fibre Channel. |
| 134 | RSVP-E2E-IGNORE. |
| 135 - 254 |
|
| 255 | Reserved. |
Header checksum. 16 bits.
A 16 bit one's complement checksum of the IP header and IP options.
Source IP address. 32 bits.
IP address of the sender.
Destination IP address. 32 bits.
IP address of the intended receiver.
Options. Variable length.
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 |
|---|---|---|---|---|---|---|---|
| C | Class | Option | |||||
C, Copy flag. 1 bit.
Indicates if the option is to be copied into all fragments.
| Value | Description |
|---|---|
| 0 | Do not copy. |
| 1 | Copy. |
Class. 2 bits.
| Value | Description |
|---|---|
| 0 | Control. |
| 1 | Reserved. |
| 2 | Debugging and measurement. |
| 3 | Reserved. |
Option. 5 bits.
| Option | Copy | Class | Value | Length | Description | References |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 1 |
End of options list. | RFC 791 |
| 1 | 0 | 0 | 1 | 1 |
NOP. | RFC 791 |
| 2 | 1 | 0 | 130 | 11 |
Security. | RFC 791, RFC 1108 |
| 3 | 1 | 0 | 131 | variable |
Loose Source Route. | RFC 791 |
| 4 | 0 | 2 | 68 | variable | Time stamp. | RFC 781, RFC 791 |
| 5 | 1 | 0 | 133 | 3 .. 31 |
Extended Security. | RFC 1108 |
| 6 | 1 | 0 | 134 | Commercial Security. | ||
| 7 | 0 | 0 | 7 | variable | Record Route. | RFC 791 |
| 8 | 1 | 0 | 136 | 4 |
Stream Identifier. | RFC 791, RFC 1122 |
| 9 | 1 | 0 | 137 | variable | Strict Source Route. | RFC 791 |
| 10 | 0 | 0 | 10 | Experimental Measurement. | ||
| 11 | 0 | 0 | 11 | 4 | MTU Probe. | RFC 1063 |
| 12 | 0 | 0 | 12 | 4 | MTU Reply. | RFC 1063 |
| 13 | 1 | 2 | 205 | Experimental Flow Control. | ||
| 14 | 1 | 0 | 142 | Expermental Access Control. | ||
| 15 | 0 | 0 | 15 | |||
| 16 | 1 | 0 | 144 | IMI Traffic Descriptor. | ||
| 17 | 1 | 0 | 145 | Extended Internet Proto | ||
| 18 | 0 | 2 | 82 | 12 | Traceroute. | RFC 1393 |
| 19 | 1 | 0 | 147 | 10 | Address Extension. | RFC 1475 |
| 20 | 1 | 0 | 148 | 4 |
Router Alert. | RFC 2113 |
| 21 | 1 | 0 | 149 | 6 .. 38 |
Selective Directed Broadcast Mode. | RFC 1770 |
| 22 | 1 | 0 | 150 | NSAP Addresses. | ||
| 23 | 1 | 0 | 151 | Dynamic Packet State. | ||
| 24 | 1 | 0 | 152 | Upstream Multicast Packet. | ||
| 25 - 31 |
Padding. Variable length.
Used as a filler to guarantee that the data starts on a 32 bit boundary.