Description:
| MAC header |
IP header |
Data ::: |
IP header:
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.
Differentiated Services.
8 bits.
This field is defined in RFC 2474 and obsoletes the TOS field.
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 |
| Codepoint |
unused |
Codepoint.
6 bits.
| Codepoint | Description | References |
| 000000 |
CS0 |
RFC 2474 |
| 001000 |
CS1 |
RFC 2474 |
| 010000 |
CS2 |
RFC 2474 |
| 011000 |
CS3 |
RFC 2474 |
| 100000 |
CS4 |
RFC 2474 |
| 101000 |
CS5 |
RFC 2474 |
| 110000 |
CS6 |
RFC 2474 |
| 111000 |
CS7 |
RFC 2474 |
| 001010 |
Assured Forwarding 11 |
RFC 2597 |
| 001100 |
Assured Forwarding 12 |
RFC 2597 |
| 001110 |
Assured Forwarding 13 |
RFC 2597 |
| 010010 |
Assured Forwarding 21 |
RFC 2597 |
| 010100 |
Assured Forwarding 22 |
RFC 2597 |
| 010110 |
Assured Forwarding 23 |
RFC 2597 |
| 011010 |
Assured Forwarding 31 |
RFC 2597 |
| 011100 |
Assured Forwarding 32 |
RFC 2597 |
| 011110 |
Assured Forwarding 33 |
RFC 2597 |
| 100010 |
Assured Forwarding 41 |
RFC 2597 |
| 100100 |
Assured Forwarding 42 |
RFC 2597 |
| 100110 |
Assured Forwarding 43 |
RFC 2597 |
| 101110 |
Expedited Forwarding PHB |
RFC 2598, RFC 3246 |
unused.
2 bits.
TOS, Type of Service.
8 bits.
Obsoleted by the Differentiated Services field.
This field 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 clears the MF bit to zero and the Fragment Offset field to zero.
Flags.
3 bits.
R, reserved.
1 bit.
Should be cleared 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 | References |
| 0 |
HOPOPT, IPv6 Hop-by-Hop Option. |
RFC 1883 |
| 1 |
ICMP, Internet Control Message Protocol. |
RFC 792 |
| 2 |
IGAP, IGMP for user Authentication Protocol.
IGMP, Internet Group Management Protocol.
RGMP, Router-port Group Management Protocol. |
RFC
1112 |
| 3 |
GGP, Gateway to Gateway Protocol. |
RFC 823 |
| 4 |
IP in IP encapsulation. |
RFC 2003 |
| 5 |
ST, Internet Stream Protocol. |
RFC 1190, RFC 1819 |
| 6 |
TCP, Transmission Control Protocol. |
RFC 793 |
| 7 |
UCL,
CBT. |
|
| 8 |
EGP, Exterior Gateway Protocol. |
RFC 888 |
| 9 |
IGRP, Interior Gateway Routing Protocol. |
|
| 10 |
BBN RCC Monitoring. |
|
| 11 |
NVP, Network Voice Protocol. |
RFC 741 |
| 12 |
PUP. |
|
| 13 |
ARGUS. |
|
| 14 |
EMCON, Emission Control Protocol. |
|
| 15 |
XNET, Cross Net Debugger. |
IEN 158 |
| 16 |
Chaos. |
|
| 17 |
UDP, User Datagram Protocol. |
RFC 768 |
| 18 |
TMux, Transport Multiplexing Protocol. |
IEN 90 |
| 19 |
DCN Measurement Subsystems. |
|
| 20 |
HMP, Host Monitoring Protocol. |
RFC 869 |
| 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. |
RFC 908 |
| 28 |
IRTP, Internet Reliable Transaction Protocol. |
RFC 938 |
| 29 |
ISO Transport Protocol Class 4. |
RFC 905 |
| 30 |
NETBLT, Network Block Transfer. |
|
| 31 |
MFE Network Services Protocol. |
|
| 32 |
MERIT Internodal Protocol. |
|
| 33 |
DCCP, Datagram Congestion Control 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. |
RFC 2473 |
| 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 |
DSR, Dynamic Source Routing Protocol. |
|
| 49 |
BNA. |
|
| 50 |
ESP, Encapsulating Security Payload. |
|
| 51 |
AH, Authentication Header. |
|
| 52 |
I-NLSP, Integrated Net Layer Security TUBA. |
|
| 53 |
SWIPE, 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 |
IPv6 Destination Options. |
|
| 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-IP. |
|
| 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 |
EtherIP. |
|
| 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. |
RFC 2393 |
| 109 |
SNP, Sitara Networks Protocol. |
|
| 110 |
Compaq Peer Protocol. |
|
| 111 |
IPX in IP. |
|
| 112 |
VRRP, Virtual Router Redundancy Protocol. |
RFC 3768, RFC 5798 |
| 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. |
RFC 3175 |
| 135 |
Mobility Header. |
RFC 3775 |
| 136 |
UDP-Lite, Lightweight User Datagram Protocol. |
RFC 3828 |
| 137 |
MPLS in IP. |
RFC 4023 |
| 138 |
MANET protocols. |
RFC 5498 |
| 139 |
HIP, Host Identity Protocol. |
RFC 5201 |
| 140 |
Shim6, Level 3 Multihoming Shim Protocol for IPv6. |
RFC 5533 |
| 141 |
WESP, Wrapped Encapsulating Security Payload. |
RFC 5840 |
| 142 |
ROHC, Robust Header Compression. |
RFC 5858 |
143
-
252 |
|
|
253
254 |
Experimentation and testing. |
|
| 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.
Padding.
Variable length.
Used as a filler to guarantee that the data starts on a 32 bit boundary.
Glossary:
Back-to-back.
(RFC 1242: 3.1)
Fixed length frames presented at a rate such that there is the minimum
legal separation for a given medium between frames over a short to medium period of time, starting from an idle state.
Bridge/router.
(RFC 1242: 3.3)
A network device that can selectively function as a router and/or a bridge based on the protocol of a specific frame.
Constant Load.
(RFC 1242: 3.4)
Fixed length frames at a fixed interval time.
Data link frame size.
(RFC 1242: 3.5)
The number of bytes in the frame from the first byte following the
preamble to the end of the FCS, if present, or to the last octet of the data if there is no FCS.
Differentiated Services.
(RFC 3140)
Differentiated Services introduces the notion of Per Hop Behaviors (PHBs) that define how traffic
belonging to a particular behavior aggregate is treated at an individual network node.
In IP packet headers, PHBs are not indicated as such; instead Differentiated Services Codepoint (DSCP) values are used.
There are only 64 possible DSCP values, but there is no such limit on the number of PHBs.
In a given network domain, there is a locally defined mapping between DSCP values and PHBs.
Standardized PHBs recommend a DSCP mapping, but network operators may choose alternative mappings.
Forward Tunnel.
(RFC 2344: 1.1)
A tunnel that shuttles packets towards the mobile node.
It starts at the home agent, and ends at the mobile node's care-of address.
Frame loss rate.
(RFC 1242: 3.6)
Percentage of frames that should have been forwarded by a network device
under steady state (constant) load that were not forwarded due to lack of resources.
Inter Frame Gap.
(RFC 1242: 3.7)
The delay from the end of a data link frame to the start of the preamble of the next data link frame.
IPv4 internet address.
A 32 bit value that contains the network and host number fields.
There are five classes of internet addresses:
The class indicates the size of the network and host fields.
Internet addresses are commonly displayed in dotted decimal notation format XXX.XXX.XXX.XXX.
| Class |
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 |
| A |
0 |
Network bits |
Host bits |
| B |
1 |
0 |
Network bits |
Host bits |
| C |
1 |
1 |
0 |
Network bits |
Host bits |
| D |
1 |
1 |
1 |
0 |
Multicast group |
| E |
1 |
1 |
1 |
1 |
0 |
reserved |
Internet address block allocation.
| Block | Description |
| 0.0.0.0/8 |
Addresses in this block refer to source hosts on "this" network.
Address 0.0.0.0/32 may be used as a source address for this host
on this network; other addresses within 0.0.0.0/8 may be used to refer to specified hosts on this network. |
| 10.0.0.0/8 |
Private use networks.
Addresses within this block should not appear on the public Internet. |
| 14.0.0.0/8 |
Public Data Networks. |
| 24.0.0.0/8 |
Cable television networks provisioning. |
| 39.0.0.0/8 |
This block was used in the "Class A Subnet Experiment" that
commenced in May 1995.
The experiment has been completed and this block has been returned to
the pool of addresses reserved for future allocation or assignment.
This block therefore no longer has a special use and is subject to
allocation to a Regional Internet Registry for assignment in the normal
manner. |
| 127.0.0.0/8 |
Loopback.
A datagram sent by a higher level protocol to an address anywhere within this block should loop back inside the host.
This is ordinarily implemented using only 127.0.0.1/32 for loopback, but no
addresses within this block should ever appear on any network anywhere. |
| 128.0.0.0/16 |
This block, corresponding to the numerically lowest of the former
Class B addresses, was initially and is still reserved by the IANA.
Given the present classless nature of the IP address space, the basis for the
reservation no longer applies and addresses in this block are subject to
future allocation to a Regional Internet Registry for assignment in the normal manner. |
| 169.254.0.0/16 |
Link Local.
It is allocated for communication between hosts on a single link.
Hosts obtain these addresses by autoconfiguration, such as when a DHCP server may not be found. |
| 172.16.0.0/12 |
Private use networks.
Addresses within this block should not appear on the public Internet. |
| 191.255.0.0/16 |
This block, corresponding to the numerically highest to the former
Class B addresses, was initially and is still reserved by the IANA.
Given the present classless nature of the IP address space, the basis for the
reservation no longer applies and addresses in this block are subject to
future allocation to a Regional Internet Registry for assignment in the normal manner. |
| 192.0.0.0/24 |
This block, corresponding to the numerically lowest of the former
Class C addresses, was initially and is still reserved by the IANA.
Given the present classless nature of the IP address space, the basis for the
reservation no longer applies and addresses in this block are subject to
future allocation to a Regional Internet Registry for assignment in the normal manner. |
| 192.0.2.0/24 |
Test-Net.
It is often used in conjunction with domain names example.com or example.net in vendor and protocol documentation.
Addresses within this block should not appear on the public Internet. |
| 192.88.99.0/24 |
6to4 relay anycast. |
| 192.168.0.0/16 |
Private use networks. Addresses within this block should not appear on the public Internet. |
| 198.18.0.0/15 |
Network interconnect device benchmark testing. |
| 223.255.255.0/24 |
This block, corresponding to the numerically highest of the former
Class C addresses, was initially and is still reserved by the IANA.
Given the present classless nature of the IP address space, the basis for the
reservation no longer applies and addresses in this block are subject to
future allocation to a Regional Internet Registry for assignment in the normal manner. |
| 224.0.0.0/4 |
Multicast. Formerly known as the Class D address space, it is allocated for use in IPv4 multicast address assignments. |
| 240.0.0.0/4 |
This block, formerly known as the Class E address space, is reserved.
The "limited broadcast" destination address 255.255.255.255
should never be forwarded outside the (sub-)net of the source.
The remainder of this space is reserved for future use. |
Internet datagram.
The data header and message that are transmitted between internet hosts.
Internet fragment.
A part of the data message with intact header fields.
Latency.
(RFC 1242: 3.8)
For store and forward devices: The time interval starting when the last
bit of the input frame reaches the input port and ending when the first bit of the output frame is seen on the output port.
For bit forwarding devices:
The time interval starting when the end of the first bit of the input frame reaches the input port and ending when
the start of the first bit of the output frame is seen on the output port.
Link Speed Mismatch.
(RFC 1242: 3.9)
Speed mismatch between input and output data rates.
Multicast.
multihomed.
A node with multiple IP addresses.
MTU, Maximum Transmission Unit.
MTU-mismatch behavior.
The MTU of the output network is smaller than the MTU of the input network. This results in
packet fragmentation.
Overhead behavior.
(RFC 1242: 3.11)
Processing done other than that for normal data frames.
Overloaded behavior.
(RFC 1242: 3.12)
When demand exceeds available system resources.
Policy based filtering.
(RFC 1242: 3.13)
The process of discarding received frames by administrative decision where normal operation would be to forward them.
Restart behavior.
(RFC 1242: 3.14)
Reinitialization of system causing data loss.
Reverse Tunnel.
(RFC 2344: 1.1)
A tunnel that starts at the mobile node's care-of address and terminates at the home agent.
Route.
Routing.
An algorithm for moving frames between connected networks.
Single frame behavior.
(RFC 1242: 3.16) One frame received on the input to a device.
Subnet.
Throughput.
(RFC 1242: 3.17)
The maximum rate at which none of the offered frames are dropped by the device.