TOC 
Network Working GroupL. Degioanni
Internet-DraftCACE Technologies
Expires: September 2, 2004F. Risso
 Politecnico di Torino
 G. Varenni
 CACE Technologies
 March 2004


PCAP Next Generation Dump File Format
PCAP-DumpFileFormat

Status of this Memo

This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work in progress.”

The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.

This Internet-Draft will expire on September 2, 2004.

Copyright Notice

Copyright © The Internet Society (2004). All Rights Reserved.

Abstract

This document describes a format to dump captured packets on a file. This format is extensible and it is currently proposed for implementation in the libpcap/WinPcap packet capture library.

Updates



Table of Contents

1.  Objectives
2.  General File Structure
    2.1.  General Block Structure
    2.2.  Block Types
    2.3.  Logical Block Hierarchy
    2.4.  Physical File Layout
    2.5.  Options
    2.6.  Data format
3.  Block Definition
    3.1.  Section Header Block (mandatory)
    3.2.  Interface Description Block (mandatory)
    3.3.  Enhanced Packet Block (optional)
    3.4.  Simple Packet Block (optional)
    3.5.  Packet Block (obsolete!)
    3.6.  Name Resolution Block (optional)
    3.7.  Interface Statistics Block (optional)
4.  Experimental Blocks (deserved to a further investigation)
    4.1.  Alternative Packet Blocks (experimental)
    4.2.  Compression Block (experimental)
    4.3.  Encryption Block (experimental)
    4.4.  Fixed Length Block (experimental)
    4.5.  Directory Block (experimental)
    4.6.  Traffic Statistics and Monitoring Blocks (experimental)
    4.7.  Event/Security Block (experimental)
5.  Recommended File Name Extension: .pcapng
6.  How to add Vendor / Domain specific extensions
7.  Conclusions
Appendix A.  Packet Block Flags Word
Appendix B.  Standardized Block Type Codes
Appendix C.  Standardized Link Type Codes
Appendix D.  Link Layer Headers
§  Authors' Addresses
§  Intellectual Property and Copyright Statements




 TOC 

1.  Objectives

The problem of exchanging packet traces becomes more and more critical every day; unfortunately, no standard solutions exist for this task right now. One of the most accepted packet interchange formats is the one defined by libpcap, which is rather old and does not fit for some of the nowadays applications particularly from the extensibility point of view.

This document proposes a new format for dumping packet traces. The following goals are being pursued:



 TOC 

2.  General File Structure



 TOC 

2.1.  General Block Structure

A capture file is organized in blocks, that are appended one to another to form the file. All the blocks share a common format, which is shown in Figure 1 (Basic block structure.).



 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          Block Type                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Block Total Length                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/                          Block Body                           /
/          /* variable length, aligned to 32 bits */            /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Block Total Length                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 1: Basic block structure. 

The fields have the following meaning:

This structure, shared among all blocks, makes it easy to process a file and to skip unneeded or unknown blocks. Some blocks can contain other blocks inside (nested blocks). Some of the blocks are mandatory, i.e. a dump file is not valid if they are not present, other are optional.

The General Block Structure allows defining other blocks if needed. A parser that does non understand them can simply ignore their content.



 TOC 

2.2.  Block Types

The currently standardized Block Type codes are specified in Appendix B (Standardized Block Type Codes), they have been grouped in the following four categories:

MANDATORY blocks must appear at least once in each file:

OPTIONAL blocks can appear in a file:

OBSOLETE blocks should not appear in newly written files (but left here for reference):

EXPERIMENTAL blocks are considered interesting but the authors believe that they deserve more in-depth discussion before being defined:



 TOC 

2.3.  Logical Block Hierarchy

The blocks build a logical hierarchy as they refer to each other. Figure 2 (Logical block Hierarchy of a pcapng file.) shows the logical hierarchy of the currently defined blocks in the form of a "tree view":



Section Header
|
+- Interface Description
|  +- Simple Packet
|  +- Enhanced Packet
|  +- Interface Statistics
|
+- Name Resolution
 Figure 2: Logical block Hierarchy of a pcapng file. 

For example: each captured packet refers to a specific capture interface, the interface itself refers to a specific section.



 TOC 

2.4.  Physical File Layout

The file must begin with a Section Header Block. However, more than one Section Header Block can be present on the dump, each one covering the data following it till the next one (or the end of file). A Section includes the data delimited by two Section Header Blocks (or by a Section Header Block and the end of the file), including the first Section Header Block.

In case an application cannot read a Section because of different version number, it must skip everything until the next Section Header Block. Note that, in order to properly skip the blocks until the next section, all blocks must have the fields Type and Length at the beginning. This is a mandatory requirement that must be maintained in future versions of the block format.

Figure 3 (File structure example: Typical configuration with a single Section Header Block.) shows a typical file configuration, with a single Section Header that covers the whole file.



+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SHB v1.0  |                      Data                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 3: File structure example: Typical configuration with a single Section Header Block. 

Figure 4 (File structure example: three Section Header Blocks in a single file.) shows a file that contains three headers, and is normally the result of file concatenation. An application that understands only version 1.0 of the file format skips the intermediate section and restart processing the packets after the third Section Header.



|--   1st Section   --|--   2nd Section   --|--  3rd Section  --|
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SHB v1.0  |  Data   | SHB V1.1  |  Data   | SHB V1.0  |  Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 4: File structure example: three Section Header Blocks in a single file. 

Figure 5 (File structure example: a pcapng file similar to a classical libpcap file.) shows a file comparable to a "classic libpcap" file - the minimum for a useful capture file. It contains a single Section Header Block (SHB), a single Interface Description Block (IDB) and a few Enhanced Packet Blocks (EPB).



+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SHB | IDB | EPB | EPB |    ...    | EPB |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 5: File structure example: a pcapng file similar to a classical libpcap file. 

Figure 6 (File structure example: more complex pcapng file.) shows a complex example file. In addition to the minimum file above, it contains packets captured from three interfaces, and also includes some Name Resolution Blocks (NRB) and an Interface Statistics Block (ISB).



+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SHB | IDB | IDB | IDB | EPB | EPB | NRB |    ...    | EPB | ISB | NRB | EPB | EPB |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 6: File structure example: more complex pcapng file. 

The last example should make it obvious, that the block structure makes the file format very flexible compared to the classical libpcap format.



 TOC 

2.5.  Options

All the block bodies have the possibility to embed optional fields. Optional fields can be used to insert some information that may be useful when reading data, but that is not really needed for packet processing. Therefore, each tool can either read the content of the optional fields (if any), or skip some of them or even all at once.

Skipping all the optional fields at once is straightforward because most of the blocks are made of a first part with fixed format, and a second optional part. Therefore, the Block Length field (present in the General Block Structure, see Section 2.1 (General Block Structure)) can be used to skip everything till the next block.

Options are a list of Type - Length - Value fields, each one containing a single value:

Options may be repeated several times (e.g. an interface that has several IP addresses associated to it) TODO: mention for each option, if it can/shouldn't appear more than one time. The option list is terminated by a Option which uses the special 'End of Option' code (opt_endofopt).

The format of the optional fields is shown in Figure 7 (Options format.).



 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Option Code              |         Option Length         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/                       Option Value                            /
/          /* variable length, aligned to 32 bits */            /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/                                                               /
/                 . . . other options . . .                     /
/                                                               /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Option Code == opt_endofopt  |  Option Length == 0          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Figure 7: Options format. 

The following codes can always be present in any optional field:

NameCodeLengthDescriptionExample(s)
opt_endofopt 0 0 It delimits the end of the optional fields. This block cannot be repeated within a given list of options.  
opt_comment 1 variable A UTF-8 string containing a comment that is associated to the current block. "This packet is the beginning of all of our problems" / "Packets 17-23 showing a bogus TCP retransmission, as reported in bugzilla entry 1486!" / "Captured at the southern plant" / "I've checked again, now it's working ok" / ...



 TOC 

2.6.  Data format

Endianess

Data contained in each section will always be saved according to the characteristics (little endian / big endian) of the dumping machine. This refers to all the fields that are saved as numbers and that span over two or more bytes.

The approach of having each section saved in the native format of the generating host is more efficient because it avoids translation of data when reading / writing on the host itself, which is the most common case when generating/processing capture dumps.

Please note: The endianess is indicated by the Section Header Block (Section Header Block (mandatory)). As this block can appear several times in a pcapng file, a single file can contain both endianess variants!

Alignment

Most (all?) fields of this specification uses proper alignment for 16- and 32-bit values. This makes it easier and faster to read/write file contents if using techniques like memory mapped files.

The alignment bytes (marked in this document e.g. with "aligned to 32 bits") should be filled with zero bytes (TODO: is this requirement a good idea for the sake of performance / do we want to allow bogus bytes here?).

Please note: 64-bit values are not aligned to 64-bit boundaries. This is because the file is naturally aligned to 32-bit boundaries only. Special care should be taken when reading and writing such values. TODO: the spec is not too consistent wrt how 64-bit values are saved. in the Packet blocks we clearly specify where the low and high 32-bits of a 64-bit timestamp should be saved. In the SHB we do use the endianess of the machine when we save the section length.

TODO - Maybe we have to specify something more here. Is what we're saying enough to avoid any kind of ambiguity?.



 TOC 

3.  Block Definition

This section details the format of the body of the blocks currently defined.



 TOC 

3.1.  Section Header Block (mandatory)

The Section Header Block is mandatory. It identifies the beginning of a section of the capture dump file. The Section Header Block does not contain data but it rather identifies a list of blocks (interfaces, packets) that are logically correlated. Its format is shown in Figure 8 (Section Header Block format.).



   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                   Block Type = 0x0A0D0D0A                     |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |                      Byte-Order Magic                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |          Major Version        |         Minor Version         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 |                                                               |
   |                          Section Length                       |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 8: Section Header Block format. 

The meaning of the fields is:

Adding new block types or options would not necessarily require that either Major or Minor numbers be changed, as code that does not know about the block type or option could just skip it; only if skipping a block or option does not work should the minor version number be changed.

Aside from the options defined in Section 2.5 (Options), the following options are valid within this block:

NameCodeLengthDescriptionExample(s)
shb_hardware 2 variable An UTF-8 string containing the description of the hardware used to create this section. "x86 Personal Computer" / "Sun Sparc Workstation" / ...
shb_os 3 variable An UTF-8 string containing the name of the operating system used to create this section. "Windows XP SP2" / "openSUSE 10.2" / ...
shb_userappl 4 variable An UTF-8 string containing the name of the application used to create this section. "dumpcap V0.99.7" / ...



 TOC 

3.2.  Interface Description Block (mandatory)

The Interface Description Block is mandatory. This block is needed to specify the characteristics of the network interface on which the capture has been made. In order to properly associate the captured data to the corresponding interface, the Interface Description Block must be defined before any other block that uses it; therefore, this block is usually placed immediately after the Section Header Block.

An Interface Description Block is valid only inside the section which it belongs to. The structure of a Interface Description Block is shown in Figure 9 (Interface Description Block format.).



    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                    Block Type = 0x00000001                    |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |           LinkType            |           Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |                            SnapLen                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 9: Interface Description Block format. 

The meaning of the fields is:

Interface ID: Tools that write / read the capture file associate a progressive 16-bit number (starting from '0') to each Interface Definition Block. This number is unique within each Section and uniquely identifies the interface (inside the current section); therefore, two Sections can have interfaces identified by the same identifiers. This unique identifier is referenced by other blocks (e.g. Packet Block) to point out the interface the block refers to (e.g. the interface that was used to capture the packet). (TODO - It would be nice, to have a "invalid Interface ID" defined, e.g. 0xFFFFFFFF)

In addition to the options defined in Section 2.5 (Options), the following options are valid within this block:

NameCodeLengthDescriptionExample(s)
if_name 2 Variable A UTF-8 string containing the name of the device used to capture data. "eth0" / "\Device\NPF_{AD1CE675-96D0-47C5-ADD0-2504B9126B68}" / ...
if_description 3 Variable A UTF-8 string containing the description of the device used to capture data. "Broadcom NetXtreme" / "First Ethernet Interface" / ...
if_IPv4addr 4 8 Interface network address and netmask. This option can be repeated multiple times within the same Interface Description Block when multiple IPv4 addresses are assigned to the interface. 192 168 1 1 255 255 255 0
if_IPv6addr 5 17 Interface network address and prefix length (stored in the last byte). This option can be repeated multiple times within the same Interface Description Block when multiple IPv6 addresses are assigned to the interface. 2001:0db8:85a3:08d3:1319:8a2e:0370:7344/64 is written (in hex) as "20 01 0d b8 85 a3 08 d3 13 19 8a 2e 03 70 73 44 40"
if_MACaddr 6 6 Interface Hardware MAC address (48 bits). 00 01 02 03 04 05
if_EUIaddr 7 8 Interface Hardware EUI address (64 bits), if available. TODO: give a good example
if_speed 8 8 Interface speed (in bps). 100000000 for 100Mbps
if_tsresol 9 1 Resolution of timestamps. If the Most Significant Bit is equal to zero, the remaining bits indicates the resolution of the timestamp as as a negative power of 10 (e.g. 6 means microsecond resolution, timestamps are the number of microseconds since 1/1/1970). If the Most Significant Bit is equal to one, the remaining bits indicates the resolution as as negative power of 2 (e.g. 10 means 1/1024 of second). If this option is not present, a resolution of 10^-6 is assumed (i.e. timestamps have the same resolution of the standard 'libpcap' timestamps). 6
if_tzone 10 4 Time zone for GMT support (TODO: specify better). TODO: give a good example
if_filter 11 variable The filter (e.g. "capture only TCP traffic") used to capture traffic. The first byte of the Option Data keeps a code of the filter used (e.g. if this is a libpcap string, or BPF bytecode, and more). More details about this format will be presented in Appendix XXX (TODO). (TODO: better use different options for different fields? e.g. if_filter_pcap, if_filter_bpf, ...) 00 "tcp port 23 and host 10.0.0.5"
if_os 12 variable A UTF-8 string containing the name of the operating system of the machine in which this interface is installed. This can be different from the same information that can be contained by the Section Header Block (Section 3.1 (Section Header Block (mandatory))) because the capture can have been done on a remote machine. "Windows XP SP2" / "openSUSE 10.2" / ...
if_fcslen 13 1 An integer value that specified the length of the Frame Check Sequence (in bits) for this interface. For link layers whose FCS length can change during time, the Packet Block Flags Word can be used (see Appendix A (Packet Block Flags Word)). 4
if_tsoffset 14 8 A 64 bits integer value that specifies an offset (in seconds) that must be added to the timestamp of each packet to obtain the absolute timestamp of a packet. If the option is missing, the timestamps stored in the packet must be considered absolute timestamps. The time zone of the offset can be specified with the option if_tzone. TODO: won't a if_tsoffset_low for fractional second offsets be useful for highly syncronized capture systems? 1234



 TOC 

3.3.  Enhanced Packet Block (optional)

An Enhanced Packet Block is the standard container for storing the packets coming from the network. The Enhanced Packet Block is optional because packets can be stored either by means of this block or the Simple Packet Block, which can be used to speed up dump generation. The format of an Enhanced Packet Block is shown in Figure 10 (Enhanced Packet Block format.).

The Enhanced Packet Block is an improvement over the original Packet Block (Packet Block (obsolete!)):



   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                    Block Type = 0x00000006                    |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |                         Interface ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |                        Timestamp (High)                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 |                        Timestamp (Low)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 |                         Captured Len                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 |                          Packet Len                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 /                                                               /
   /                          Packet Data                          /
   /          /* variable length, aligned to 32 bits */            /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 10: Enhanced Packet Block format. 

The Enhanced Packet Block has the following fields:

In addition to the options defined in Section 2.5 (Options) and in the Packet Block, the following options are valid within this block:

NameCodeLengthDescriptionExample(s)
epb_flags 2 4 A flags word containing link-layer information. A complete specification of the allowed flags can be found in Appendix A (Packet Block Flags Word). 0
epb_hash 3 variable This option contains a hash of the packet. The first byte specifies the hashing algorithm, while the following bytes contain the actual hash, whose size depends on the hashing algorithm, and hence from the value in the first bit. The hashing algorithm can be: 2s complement (algorithm byte = 0, size=XXX), XOR (algorithm byte = 1, size=XXX), CRC32 (algorithm byte = 2, size = 4), MD-5 (algorithm byte = 3, size=XXX), SHA-1 (algorithm byte = 4, size=XXX). The hash covers only the packet, not the header added by the capture driver: this gives the possibility to calculate it inside the network card. The hash allows easier comparison/merging of different capture files, and reliable data transfer between the data acquisition system and the capture library. (TODO: the text above uses "first bit", but shouldn't this be "first byte"?!?) TODO: give a good example
epb_dropcount 4 8 A 64bit integer value specifying the number of packets lost (by the interface and the operating system) between this packet and the preceding one. 0



 TOC 

3.4.  Simple Packet Block (optional)

The Simple Packet Block is a lightweight container for storing the packets coming from the network. Its presence is optional.

A Simple Packet Block is similar to a Packet Block (see Section 3.5 (Packet Block (obsolete!))), but it is smaller, simpler to process and contains only a minimal set of information. This block is preferred to the standard Packet Block when performance or space occupation are critical factors, such as in sustained traffic dump applications. A capture file can contain both Packet Blocks and Simple Packet Blocks: for example, a capture tool could switch from Packet Blocks to Simple Packet Blocks when the hardware resources become critical.

The Simple Packet Block does not contain the Interface ID field. Therefore, it must be assumed that all the Simple Packet Blocks have been captured on the interface previously specified in the first Interface Description Block.

Figure 11 (Simple Packet Block format.) shows the format of the Simple Packet Block.



    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                    Block Type = 0x00000003                    |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |                          Packet Len                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 /                                                               /
   /                          Packet Data                          /
   /          /* variable length, aligned to 32 bits */            /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 11: Simple Packet Block format. 

The Simple Packet Block has the following fields:

The Simple Packet Block does not contain the timestamp because this is often one of the most costly operations on PCs. Additionally, there are applications that do not require it; e.g. an Intrusion Detection System is interested in packets, not in their timestamp.

A Simple Packet Block cannot be present in a Section that has more than one interface because of the impossibility to refer to the correct one (it does not contain any Interface ID field).

The Simple Packet Block is very efficient in term of disk space: a snapshot whose length is 100 bytes requires only 16 bytes of overhead, which corresponds to an efficiency of more than 86%.



 TOC 

3.5.  Packet Block (obsolete!)

The Packet Block is marked obsolete, better use the Enhanced Packet Block instead!

A Packet Block is the standard container for storing the packets coming from the network. The Packet Block is optional because packets can be stored either by means of this block or the Simple Packet Block, which can be used to speed up dump generation. The format of a packet block is shown in Figure 12 (Packet Block format.).



    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                    Block Type = 0x00000002                    |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |         Interface ID          |          Drops Count          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |                        Timestamp (High)                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 |                        Timestamp (Low)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 |                         Captured Len                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 |                          Packet Len                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 /                                                               /
   /                          Packet Data                          /
   /          /* variable length, aligned to 32 bits */            /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 12: Packet Block format. 

The Packet Block has the following fields:

In addition to the options defined in Section 2.5 (Options), the following options are valid within this block:



NameCodeLengthDescriptionExample(s)
pack_flags 2 4 Same as epb_flags of the enhanced packet block. 0
pack_hash 3 variable Same as epb_hash of the enhanced packet block. TODO: give a good example

 Table 1 



 TOC 

3.6.  Name Resolution Block (optional)

The Name Resolution Block is used to support the correlation of numeric addresses (present in the captured packets) and their corresponding canonical names and it is optional. Having the literal names saved in the file, this prevents the need of a name resolution in a delayed time, when the association between names and addresses can be different from the one in use at capture time. Moreover, the Name Resolution Block avoids the need of issuing a lot of DNS requests every time the trace capture is opened, and allows to have name resolution also when reading the capture with a machine not connected to the network.

A Name Resolution Block is normally placed at the beginning of the file, but no assumptions can be taken about its position. Name Resolution Blocks can be added in a second time by tools that process the file, like network analyzers.

The format of the Name Resolution Block is shown in Figure 13 (Name Resolution Block format.).



    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                    Block Type = 0x00000004                    |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |      Record Type              |         Record Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 /                       Record Value                            /
   /          /* variable length, aligned to 32 bits */            /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                  . . . other records . . .                    .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Record Type == end_of_recs   |  Record Length == 00          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 13: Name Resolution Block format. 

The Name Resolution Block has the following fields:

This is followed by a zero-terminated list of records (in the TLV format), each of which contains an association between a network address and a name. There are three possible types of records:



NameCodeLengthDescriptionExample(s)
nres_endofrecord 0 0 It delimits the end of name resolution records. This record is needed to determine when the list of name resolution records has ended and some options (if any) begin.  
nres_ip4record 1 Variable Specifies an IPv4 address (contained in the first 4 bytes), followed by one or more zero-terminated strings containing the DNS entries for that address. 127 0 0 1 "localhost"
nres_ip6record 2 Variable Specifies an IPv6 address (contained in the first 16 bytes), followed by one or more zero-terminated strings containing the DNS entries for that address. TODO: give a good example

 Table 2 

Each Record Value is aligned to a 32-bit boundary. The corresponding Record Length reflects the actual length of the Record Value.

After the list of Name Resolution Records, optionally, a list of options (formatted according to the rules defined in Section 2.5 (Options)) can be present.

In addiction to the options defined in Section 2.5 (Options), the following options are valid within this block:

NameCodeLengthDescriptionExample(s)
ns_dnsname 2 Variable A UTF-8 string containing the name of the machine (DNS server) used to perform the name resolution. "our_nameserver"
ns_dnsIP4addr 3 4 The IPv4 address of the DNS server. 192 168 0 1
ns_dnsIP6addr 4 16 The IPv6 address of the DNS server. TODO: give a good example

TODO: Add an "Interface ID" option, if the name resolution is only valid for a specific interface?

TODO: Does it make sense to have two "optional mechanisms" (records vs. options) here?



 TOC 

3.7.  Interface Statistics Block (optional)

The Interface Statistics Block contains the capture statistics for a given interface and it is optional. The statistics are referred to the interface defined in the current Section identified by the Interface ID field. An Interface Statistics Block is normally placed at the end of the file, but no assumptions can be taken about its position - it can even appear multiple times for the same interface.

The format of the Interface Statistics Block is shown in Figure 14 (Interface Statistics Block format.).



    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------------------------------------------------------+
 0 |                   Block Type = 0x00000005                     |
   +---------------------------------------------------------------+
 4 |                      Block Total Length                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 8 |                         Interface ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |                        Timestamp (High)                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 |                        Timestamp (Low)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 /                                                               /
   /                      Options (variable)                       /
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Block Total Length                       |
   +---------------------------------------------------------------+
 Figure 14: Interface Statistics Block format. 

The fields have the following meaning:

All the statistic fields are defined as options in order to deal with systems that do not have a complete set of statistics. Therefore, In addiction to the options defined in Section 2.5 (Options), the following options are valid within this block:

NameCodeLengthDescriptionTODO: give a good example
isb_starttime 2 8 Time in which the capture started; time will be stored in two blocks of four bytes each. The format of the timestamp is the same already defined in the Enhanced Packet Block (Section 3.3 (Enhanced Packet Block (optional))). TODO: give a good example
isb_endtime 3 8 Time in which the capture ended; ; time will be stored in two blocks of four bytes each. The format of the timestamp is the same already defined in the Enhanced Packet Block (Section 3.3 (Enhanced Packet Block (optional))). TODO: give a good example
isb_ifrecv 4 8 Number of packets received from the physical interface starting from the beginning of the capture. 100
isb_ifdrop 5 8 Number of packets dropped by the interface due to lack of resources starting from the beginning of the capture. 0
isb_filteraccept 6 8 Number of packets accepted by filter starting from the beginning of the capture. 100
isb_osdrop 7 8 Number of packets dropped by the operating system starting from the beginning of the capture. 0
isb_usrdeliv 8 8 Number of packets delivered to the user starting from the beginning of the capture. The value contained in this field can be different from the value 'isb_filteraccept - isb_osdrop' because some packets could still lay in the OS buffers when the capture ended. 0

All the fields that refer to packet counters are 64-bit values, represented with the byte order of the current section. Special care must be taken in accessing these fields: since all the blocks are aligned to a 32-bit boundary, such fields are not guaranteed to be aligned on a 64-bit boundary.



 TOC 

4.  Experimental Blocks (deserved to a further investigation)



 TOC 

4.1.  Alternative Packet Blocks (experimental)

Can some other packet blocks (besides the ones described in the previous paragraphs) be useful?



 TOC 

4.2.  Compression Block (experimental)

The Compression Block is optional. A file can contain an arbitrary number of these blocks. A Compression Block, as the name says, is used to store compressed data. Its format is shown in Figure 15 (Compression Block format.).



 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------------------------------------------------------+
|                        Block Type = ?                         |
+---------------------------------------------------------------+
|                      Block Total Length                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Compr. Type  |                                               |
+-+-+-+-+-+-+-+-+                                               |
|                                                               |
|                       Compressed Data                         |
|                                                               |
|              /* variable length, byte-aligned */              |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Block Total Length                       |
+---------------------------------------------------------------+
 Figure 15: Compression Block format. 

The fields have the following meaning:



 TOC 

4.3.  Encryption Block (experimental)

The Encryption Block is optional. A file can contain an arbitrary number of these blocks. An Encryption Block is used to store encrypted data. Its format is shown in Figure 16 (Encryption Block format.).



 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------------------------------------------------------+
|                        Block Type = ?                         |
+---------------------------------------------------------------+
|                      Block Total Length                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Encr. Type  |                                               |
+-+-+-+-+-+-+-+-+                                               |
|                                                               |
|                       Encrypted Data                          |
|                                                               |
|              /* variable length, byte-aligned */              |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Block Total Length                       |
+---------------------------------------------------------------+
 Figure 16: Encryption Block format. 

The fields have the following meaning:



 TOC 

4.4.  Fixed Length Block (experimental)

The Fixed Length Block is optional. A file can contain an arbitrary number of these blocks. A Fixed Length Block can be used to optimize the access to the file. Its format is shown in Figure 17 (Fixed Length Block format.). A Fixed Length Block stores records with constant size. It contains a set of Blocks (normally Packet Blocks or Simple Packet Blocks), of wihich it specifies the size. Knowing this size a priori helps to scan the file and to load some portions of it without truncating a block, and is particularly useful with cell-based networks like ATM.



 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------------------------------------------------------+
|                        Block Type = ?                         |
+---------------------------------------------------------------+
|                      Block Total Length                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Cell Size            |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
|                                                               |
|                        Fixed Size Data                        |
|                                                               |
|              /* variable length, byte-aligned */              |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Block Total Length                       |
+---------------------------------------------------------------+
 Figure 17: Fixed Length Block format. 

The fields have the following meaning:



 TOC 

4.5.  Directory Block (experimental)

If present, this block contains the following information:

A directory block must be followed by at least N packets, otherwise it must be considered invalid. It can be used to efficiently load portions of the file to memory and to support operations on memory mapped files. This block can be added by tools like network analyzers as a consequence of file processing.



 TOC 

4.6.  Traffic Statistics and Monitoring Blocks (experimental)

One or more blocks could be defined to contain network statistics or traffic monitoring information. They could be use to store data collected from RMON or Netflow probes, or from other network monitoring tools.



 TOC 

4.7.  Event/Security Block (experimental)

This block could be used to store events. Events could contain generic information (for example network load over 50%, server down...) or security alerts. An event could be:



 TOC 

5.  Recommended File Name Extension: .pcapng

The recommended file name extension for the "PCAP Next Generation Dump File Format" specified in this document is ".pcapng".

At least in the "Windows world", files are distinguished by an extension to their filename. Such an extension is technically not actually required, as applications should be able to automatically detect the pcapng file format through the "magic bytes" at the beginning of the file. However, using name extensions makes it easier to work with files (e.g. visually distinguish file formats) so it is recommended - though not required - to use .pcapng as the name extension for files following this specification.

Please note: To avoid confusion (like the current usage of .cap for a pletora of different capture file formats) other file name extensions than .pcapng should be avoided!



 TOC 

6.  How to add Vendor / Domain specific extensions

TODO - explain the preferred way to add new block types and new options for existing blocks in more detail.



 TOC 

7.  Conclusions

The file format proposed in this document should be very versatile and satisfy a wide range of applications. In the simplest case, it can contain a raw dump of the network data, made of a series of Simple Packet Blocks. In the most complex case, it can be used as a repository for heterogeneous information. In every case, the file remains easy to parse and an application can always skip the data it is not interested in; at the same time, different applications can share the file, and each of them can benefit of the information produced by the others. Two or more files can be concatenated obtaining another valid file.



 TOC 

Appendix A.  Packet Block Flags Word

The Packet Block Flags Word is a 32-bit value that contains link-layer information about the packet.

The meaning of the bits is the following:

Bit NumberDescription
0-1 Inbound / Outbound packet (00 = information not available, 01 = inbound, 10 = outbound)
2-4 Reception type (000 = not specified, 001 = unicast, 010 = multicast, 011 = broadcast, 100 = promiscuous).
5-8 FCS length, in bytes (0000 if this information is not available). This value overrides the if_fcslen option of the Interface Description Block, and is used with those link layers (e.g. PPP) where the length of the FCS can change during time.
9-15 Reserved (must be set to zero).
16-31 link-layer-dependent errors (Bit 31 = symbol error, Bit 30 = preamble error, Bit 29 = Start Frame Delimiter error, Bit 28 = unaligned frame error, Bit 27 = wrong Inter Frame Gap error, Bit 26 = packet too short error, Bit 25 = packet too long error, Bit 24 = CRC error, other?? are 16 bit enough?).



 TOC 

Appendix B.  Standardized Block Type Codes

Every Block is uniquely identified by a 32 bit integer value, stored in the Block Header.

As pointed out in Section 2.1 (General Block Structure), Block Types codes whose Most Significant Bit (bit 31) is set to 1 are reserved for local use by the application.

All the remaining Block Type codes (0x00000000 to 0x7FFFFFFF) are standardized by this document. A request should be sent to the authors of this document to add a new Standard Block Type code to the specification.

Here is a list of the Standardized Block Type Codes.

Block Type CodeDescription
0x00000000 Reserved ???
0x00000001 Interface Description Block (Interface Description Block (mandatory))
0x00000002 Packet Block (Packet Block (obsolete!))
0x00000003 Simple Packet Block (Simple Packet Block (optional))
0x00000004 Name Resolution Block (Name Resolution Block (optional))
0x00000005 Interface Statistics Block (Interface Statistics Block (optional))
0x00000006 Enhanced Packet Block (Enhanced Packet Block (optional))
0x00000007 IRIG Timestamp Block (requested by Gianluca Varenni <[email protected]>, CACE Technologies LLC)
0x00000008 Arinc 429 in AFDX Encapsulation Information Block (requested by Gianluca Varenni <[email protected]>, CACE Technologies LLC)
0x0A0D0D0A Section Header Block (Section Header Block (mandatory))
0x0A0D0A00-0x0A0D0AFF Reserved. Used to detect trace files corrupted because of file transfers using the HTTP protocol in text mode.
0x000A0D0A-0xFF0A0D0A Reserved. Used to detect trace files corrupted because of file transfers using the HTTP protocol in text mode.
0x000A0D0D-0xFF0A0D0D Reserved. Used to detect trace files corrupted because of file transfers using the HTTP protocol in text mode.
0x0D0D0A00-0x0D0D0AFF Reserved. Used to detect trace files corrupted because of file transfers using the FTP protocol in text mode.



 TOC 

Appendix C.  Standardized Link Type Codes

NOTE: we should decide if we want to have this list here or in a separate document. It may make sense to have this list in a separate document and describe the format of a frame for each different linktype, or specify that the frame format is proprietary of a company and not public. There are a large number of encapsulations that are really vague and unspecified at all (even the name does not make any sense). Moreover, we should decide if we want to have *all* the linktypes (LINKTYPE_XXX) defined by libpcap, or just a subset of them, thus trying to remove the big mess and confusion of similar headers.

Here is a list of the Standardized Link Type Codes.

Link Type NameLink Type CodeDescription
LINKTYPE_NULL 0 No link layer information. A packet saved with this link layer contains a raw L3 packet preceded by a 32-bit host-byte-order AF_ value indicating the specific L3 type.
LINKTYPE_ETHERNET 1 D/I/X and 802.3 Ethernet
LINKTYPE_EXP_ETHERNET 2 Experimental Ethernet (3Mb)
LINKTYPE_AX25 3 Amateur Radio AX.25
LINKTYPE_PRONET 4 Proteon ProNET Token Ring
LINKTYPE_CHAOS 5 Chaos
LINKTYPE_TOKEN_RING 6 IEEE 802 Networks
LINKTYPE_ARCNET 7 ARCNET, with BSD-style header
LINKTYPE_SLIP 8 Serial Line IP
LINKTYPE_PPP 9 Point-to-point Protocol
LINKTYPE_FDDI 10 FDDI
LINKTYPE_PPP_HDLC 50 PPP in HDLC-like framing
LINKTYPE_PPP_ETHER 51 NetBSD PPP-over-Ethernet
LINKTYPE_SYMANTEC_FIREWALL 99 Symantec Enterprise Firewall
LINKTYPE_ATM_RFC1483 100 LLC/SNAP-encapsulated ATM
LINKTYPE_RAW 101 Raw IP
LINKTYPE_SLIP_BSDOS 102 BSD/OS SLIP BPF header
LINKTYPE_PPP_BSDOS 103 BSD/OS PPP BPF header
LINKTYPE_C_HDLC 104 Cisco HDLC
LINKTYPE_IEEE802_11 105 IEEE 802.11 (wireless)
LINKTYPE_ATM_CLIP 106 Linux Classical IP over ATM
LINKTYPE_FRELAY 107 Frame Relay
LINKTYPE_LOOP 108 OpenBSD loopback
LINKTYPE_ENC 109 OpenBSD IPSEC enc
LINKTYPE_LANE8023 110 ATM LANE + 802.3 (Reserved for future use)
LINKTYPE_HIPPI 111 NetBSD HIPPI (Reserved for future use)
LINKTYPE_HDLC 112 NetBSD HDLC framing (Reserved for future use)
LINKTYPE_LINUX_SLL 113 Linux cooked socket capture
LINKTYPE_LTALK 114 Apple LocalTalk hardware
LINKTYPE_ECONET 115 Acorn Econet
LINKTYPE_IPFILTER 116 Reserved for use with OpenBSD ipfilter
LINKTYPE_PFLOG 117 OpenBSD DLT_PFLOG
LINKTYPE_CISCO_IOS 118 For Cisco-internal use
LINKTYPE_PRISM_HEADER 119 802.11+Prism II monitor mode
LINKTYPE_AIRONET_HEADER 120 FreeBSD Aironet driver stuff
LINKTYPE_HHDLC 121 Reserved for Siemens HiPath HDLC
LINKTYPE_IP_OVER_FC 122 RFC 2625 IP-over-Fibre Channel
LINKTYPE_SUNATM 123 Solaris+SunATM
LINKTYPE_RIO 124 RapidIO - Reserved as per request from Kent Dahlgren <[email protected]> for private use.
LINKTYPE_PCI_EXP 125 PCI Express - Reserved as per request from Kent Dahlgren <[email protected]> for private use.
LINKTYPE_AURORA 126 Xilinx Aurora link layer - Reserved as per request from Kent Dahlgren <[email protected]> for private use.
LINKTYPE_IEEE802_11_RADIO 127 802.11 plus BSD radio header
LINKTYPE_TZSP 128 Tazmen Sniffer Protocol - Reserved for the TZSP encapsulation, as per request from Chris Waters <[email protected]> TZSP is a generic encapsulation for any other link type, which includes a means to include meta-information with the packet, e.g. signal strength and channel for 802.11 packets.
LINKTYPE_ARCNET_LINUX 129 Linux-style headers
LINKTYPE_JUNIPER_MLPPP 130 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_MLFR 131 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_ES 132 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_GGSN 133 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_MFR 134 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_ATM2 135 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_SERVICES 136 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_JUNIPER_ATM1 137 Juniper-private data link type, as per request from Hannes Gredler <[email protected]>. The corresponding DLT_s are used for passing on chassis-internal metainformation such as QOS profiles, etc..
LINKTYPE_APPLE_IP_OVER_IEEE1394 138 Apple IP-over-IEEE 1394 cooked header
LINKTYPE_MTP2_WITH_PHDR 139 ???
LINKTYPE_MTP2 140 ???
LINKTYPE_MTP3 141 ???
LINKTYPE_SCCP 142 ???
LINKTYPE_DOCSIS 143 DOCSIS MAC frames
LINKTYPE_LINUX_IRDA 144 Linux-IrDA
LINKTYPE_IBM_SP 145 Reserved for IBM SP switch and IBM Next Federation switch.
LINKTYPE_IBM_SN 146 Reserved for IBM SP switch and IBM Next Federation switch.



 TOC 

Appendix D.  Link Layer Headers

The Packet Data field of the Packet Blocks won't start with the actual network data captured, but with some link type specific "meta data". The format of this meta data depends on the link type used. TODO: mention example code in libpcap that lists these link headers.



 TOC 

Authors' Addresses

  Loris Degioanni
  CACE Technologies
  1949 Fifth Street #103
  Davis, CA 95616
  United States
Phone:  +1 530 758 2790
Email:  [email protected]
URI:  http://www.winpcap.org/loris/
  
  Fulvio Risso
  Politecnico di Torino
  Corso Duca degli Abruzzi, 24
  Torino 10129
  Italy
Phone:  +39 011 564 7008
Email:  [email protected]
URI:  http://staff.polito.it/fulvio.risso/
  
  Gianluca Varenni
  CACE Technologies
  1949 Fifth Street #103
  Davis, CA 95616
  United States
Phone:  +1 530 758 2790
Email:  [email protected]
URI:  http://www.winpcap.org/gianluca/


 TOC 

Full Copyright Statement

Intellectual Property

Acknowledgment