| Internet-Draft | pcaplinktype | April 2025 |
| Harris & Richardson | Expires 21 October 2025 | [Page] |
This document describes a set of PCAP-related LINKTYPE values and creates an IANA registry for those values.¶
This note is to be removed before publishing as an RFC.¶
Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-opsawg-pcaplinktype/.¶
Discussion of this document takes place on the opsawg Working Group mailing list (mailto:opsawg@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/opsawg/. Subscribe at https://www.ietf.org/mailman/listinfo/opsawg/.¶
Source for this draft and an issue tracker can be found at https://github.com/IETF-OPSAWG-WG/pcapng.¶
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In the late 1980's, Van Jacobson, Steve McCanne, and others at the Network Research Group at Lawrence Berkeley National Laboratory developed the tcpdump program to capture and dissect network traces. The code to capture traffic, using low-level mechanisms in various operating systems, and to read and write network traces to a file was later put into a library named libpcap [LIBPCAP].¶
Other documents describe the original (legacy) file format used by tcpdump (PCAP, [I-D.ietf-opsawg-pcap]), as well as a revised file format [I-D.ietf-opsawg-pcapng], both of which are used by tcpdump and Wireshark [Wireshark].¶
Within those file formats each packet that is captured is indicated by a LINKTYPE value. The LINKTYPE value selects one of many hundred formats for metadata and Layer 2 encapsulation of the packet.¶
This document creates an IANA registry for LINKTYPE values, establishing the IANA Considerations by which other uses of the PCAP-related formats may register new LINKTYPE values.¶
IANA is requested to create a new registry group entitled "The PCAP Registry".¶
IANA is also requested to create a registry entitled "PCAP-related LinkType List" under The PCAP registry group (Section 2.1).¶
The registry has the following structure:¶
LINKTYPE Name: Indicates the symbolic name for this LinkType. The name is prefixed with "LINKTYPE_" (i.e., LINKTYPE_something).¶
LINKTYPE Value: Indicates the 16-bit unsigned integer assigned for this LinkType.¶
Description: Provides a very short description.¶
Reference: Indicates an authoritative document reference for the LinkType or a requester reference.¶
The policy allocation for the LinkType values is as follows:¶
Values from 32768 to 65000 must be allocated via Specification Required (Section 4.6 of [RFC8126]). Guidance for Designated Experts is provided in Section 2.2.2.¶
Values from 0 to 32767 are allocated following a First-Come First-Served policy (Section 4.4 of [RFC8126]). Note that this category includes the historical allocations which have an uneven level of definition.¶
Values from 65001 to 65535 are reserved for Private Use (Section 4.1 of [RFC8126]).¶
The initial version of the registry is provided in Section 2.2.1. In each case here, the reference should be set to [TCPDUMP] and the RFC number to be assigned to this document, which is not repeated each time.¶
The initial contents of the table are based upon the Link type list maintained by libpcap, and published on [TCPDUMP].¶
Note that historically, values were assigned incrementally following First Come First Served (FCFS) policy, with a preference for a public specification, but with no mandate. Some historical values may have less specification than desired.¶
LinkType values 147 to 162 named LINKTYPE_RESERVED_xx were originally reserved for Private Use. Their use is Deprecated in favour of the values in the 65001-65535 range.¶
In general, Private Use values should never leak out of the entity that uses it. As the FCFS range is large and easily obtained, official values are recommended.¶
There is often an associated Data Link Type (DLT) value which is often identical in value, but not universally so. DLT values are associated with specific operation system captures, and are operating system specific, and are thus not subject to standardization.¶
This is the initial table for the registry:¶
LINKTYPE_ARCNET_BSD¶
7¶
Reserved for ARCNET Data Packets with BSD encapsulation¶
LINKTYPE_IEEE802_11_PRISM¶
119¶
IEEE 802.11 wireless LAN, preceded by a Prism monitor mode header¶
LINKTYPE_IEEE802_11_AIRONET¶
120¶
Reserved for 802.11 + FreeBSD Aironet radio metadata¶
LINKTYPE_IEEE802_11_RADIOTAP¶
127¶
IEEE 802.11 wireless LAN, preceded by a Radiotap header¶
LINKTYPE_ARCNET_LINUX¶
129¶
Reserved for ARCNET Data Packets with Linux encapsulation¶
LINKTYPE_APPLE_IP_OVER_IEEE1394¶
138¶
Apple IP-over-IEEE 1394 cooked header¶
LINKTYPE_MTP2_WITH_PHDR¶
139¶
SS7 MTP2 frames, with a pseudo-header¶
LINKTYPE_IEEE802_11_AVS¶
163¶
IEEE 802.11 wireless LAN, preceded by an AVS header¶
LINKTYPE_PPP_PPPD¶
166¶
PPP preceded by a direction octet and an HDLC-like control field¶
LINKTYPE_GPRS_LLC¶
169¶
General Packet Radio Service Logical Link Control, as per 3GPP TS 04.64¶
LINKTYPE_GPF_T¶
170¶
Transparent-mapped generic framing procedure¶
LINKTYPE_GCOM_SERIAL¶
173¶
Reserved for Gcom T1/E1 line monitoring equipment¶
LINKTYPE_A653_ICM¶
185¶
Reserved for Arinc 653 Interpartition Communication messages¶
LINKTYPE_BLUETOOTH_HCI_H4¶
187¶
Bluetooth HCI UART Transport Layer packets¶
LINKTYPE_IEEE802_16_MAC_CPS¶
188¶
Reserved for IEEE 802.16 MAC Common Part Sublayer¶
LINKTYPE_USB_LINUX¶
189¶
USB packets, beginning with a Linux USB header¶
LINKTYPE_CAN20B¶
190¶
Reserved for Controller Area Network (CAN) v. 2.0B packets¶
LINKTYPE_IEEE802_15_4_LINUX¶
191¶
Reserved for IEEE 802.15.4 with address fields padded by Linux¶
LINKTYPE_PPI¶
192¶
Per-Packet Information header preceding packet data¶
LINKTYPE_IEEE802_16_MAC_CPS_RADIO¶
193¶
Reserved for 802.16 MAC Common Part Sublayer plus radio header¶
LINKTYPE_SITA¶
196¶
Various link-layer types, with a pseudo-header¶
LINKTYPE_RAIF1¶
198¶
Reserved for Ethernet packets captured from a u10 Networks board¶
LINKTYPE_IPMB_KONTRON¶
199¶
Reserved for IPMB packet for IPMI, with a 2-octet header¶
LINKTYPE_BLUETOOTH_HCI_H4_WITH_PHDR¶
201¶
Bluetooth HCI UART Transport Layer packets with a direction pseudo-header¶
LINKTYPE_AX25_KISS¶
202¶
KISS frames between a host and an AX.25 TNC¶
LINKTYPE_C_HDLC_WITH_DIR¶
205¶
Cisco PPP with HDLC framing, with a direction header¶
LINKTYPE_FRELAY_WITH_DIR¶
206¶
Frame Relay LAPF, with a direction header¶
LINKTYPE_FLEXRAY¶
210¶
FlexRay frames or symbols, with a pseudo-header¶
LINKTYPE_MOST¶
211¶
Reserved for Media Oriented Systems Transport (MOST) bus¶
LINKTYPE_LIN¶
212¶
Local Interconnect Network (LIN) automotive bus, with a metadata header¶
LINKTYPE_IEEE802_15_4_NONASK_PHY¶
215¶
IEEE 802.15.4 with PHY header¶
LINKTYPE_GSMTAP_ABIS¶
218¶
Reserved for GSM Abis interface, with gsmtap header¶
LINKTYPE_USB_LINUX_MMAPPED¶
220¶
USB packets, beginning with an extended Linux USB header¶
LINKTYPE_WIHART¶
223¶
Reserved for Wireless HART (Highway Addressable Remote Transducer)¶
LINKTYPE_FC_2_WITH_FRAME_DELIMS¶
225¶
Fibre Channel FC-2 frames with SOF and EOF¶
LINKTYPE_CAN_SOCKETCAN¶
227¶
Controller Area Network (CAN) frames, with a metadata header¶
LINKTYPE_MUX27010¶
236¶
Variant of 3GPP TS 27.010 multiplexing protocol¶
LINKTYPE_NFLOG¶
239¶
Linux netlink NETLINK NFLOG socket log messages¶
LINKTYPE_NETANALYZER¶
240¶
Ethernet frames with netANALYZER pseudo-header¶
LINKTYPE_NETANALYZER_TRANSPARENT¶
241¶
Ethernet frames with netANALYZER pseudo-header, preamble, and SFD¶
LINKTYPE_MPEG_2_TS¶
243¶
MPEG-2 Transport Stream transport packets¶
LINKTYPE_NFC_LLCP¶
245¶
NFC Logical Link Control Protocol frames, with a pseudo-header¶
LINKTYPE_SCTP¶
248¶
SCTP packets, with no lower-level protocols such as IPv4 or IPv6¶
LINKTYPE_USBPCAP¶
249¶
USB packets, beginning with a USBPcap header¶
LINKTYPE_RTAC_SERIAL¶
250¶
Serial-line packet from the Schweitzer Engineering Laboratories RTAC product¶
LINKTYPE_BLUETOOTH_LE_LL¶
251¶
Bluetooth Low Energy link-layer packets¶
LINKTYPE_BLUETOOTH_BREDR_BB¶
255¶
Bluetooth Basic Rate and Enhanced Data Rate baseband packets¶
LINKTYPE_BLUETOOTH_LE_LL_WITH_PHDR¶
256¶
Bluetooth Low Energy link-layer packets¶
LINKTYPE_EPON¶
259¶
Ethernet-over-passive-optical-network packets, including preamble octets¶
LINKTYPE_WATTSTOPPER_DLM¶
263¶
WattStopper Digital Lighting Management (DLM) and Legrand Nitoo Open protocol packets¶
LINKTYPE_ISO_14443¶
264¶
ISO 14443 contactless smartcard messages¶
LINKTYPE_USB_DARWIN¶
266¶
USB packets captured on a Darwin-based operating system (macOS, etc.)¶
LINKTYPE_TI_LLN_SNIFFER¶
269¶
Reserved for Texas Instruments protocol sniffer¶
LINKTYPE_LORATAP¶
270¶
LoRaWan packets with a LoRaTap pseudo-header¶
LINKTYPE_VSOCK¶
271¶
Protocol for communication between host and guest machines in VMware and KVM hypervisors¶
LINKTYPE_NORDIC_BLE¶
272¶
Messages to and from a Nordic Semiconductor nRF Sniffer for Bluetooth LE packets¶
LINKTYPE_DOCSIS31_XRA31¶
273¶
DOCSIS packets and bursts, preceded by a pseudo-header¶
LINKTYPE_DISPLAYPORT_AUX¶
275¶
DisplayPort AUX channel monitoring messages¶
LINKTYPE_EBHSCR¶
279¶
Elektrobit High Speed Capture and Replay (EBHSCR) format¶
LINKTYPE_VPP_DISPATCH¶
280¶
fd.io VPP graph dispatcher trace records¶
LINKTYPE_DSA_TAG_BRCM¶
281¶
Ethernet frames, with a Broadcom switch tag inserted¶
LINKTYPE_DSA_TAG_BRCM_PREPEND¶
282¶
Ethernet frames, with a Broadcom switch tag prepended¶
LINKTYPE_IEEE802_15_4_TAP¶
283¶
IEEE 802.15.4 with a tap header preceding it¶
LINKTYPE_DSA_TAG_DSA¶
284¶
Ethernet frames, with a Marvell DSA switch tag inserted¶
LINKTYPE_DSA_TAG_EDSA¶
285¶
Ethernet frames, with a Marvell EDSA switch tag inserted¶
LINKTYPE_Z_WAVE_SERIAL¶
287¶
Serial frames transmitted between a host and a Z-Wave chip over an RS-232 or USB serial connection¶
[Z_WAVE_SERIAL] section 5¶
LINKTYPE_NETANALYZER_NG¶
291¶
Reserved for Hilscher Gesellschaft fuer Systemautomation mbH netANALYZER NG hardware and software¶
LINKTYPE_ZBOSS_NCP¶
292¶
ZBOSS NCP Serial Protocol, with a pseudo-header¶
LINKTYPE_USB_2_0_LOW_SPEED¶
293¶
Low-Speed USB 2.0, 1.1, or 1.0 packets¶
LINKTYPE_USB_2_0_FULL_SPEED¶
294¶
Full-Speed USB 2.0, 1.1, or 1.0 packets¶
LINKTYPE_SILABS_DEBUG_CHANNEL¶
298¶
Silicon Labs debug channel protocol¶
LINKTYPE_FIRA_UCI¶
299¶
Ultra-wideband (UWB) controller interface protocol (UCI)¶
When processing a request for a Specification Required allocation the Designated Experts are expected to be able to find the relevant specification at a clearly stable URL. It is noted that many enterprise web sites do not maintain URLs over a long period of time, and a document in a "wp-uploaded" section is highly likely to disappear. In addition specifications that require a reader to click through any kind of marketing or legal agreement are not considered public.¶
The specification needs to be clearly written, and when the contents of the link type can contain an IPv4 or IPv6 header, then the octets between the beginning of the link type and the IP header needs to be very clearly specified in that document.¶
Specifications that are not publicly available, but which may be obtained via liaison agreements (such as to ITU-T, 3GPP, IEEE, etc.) are acceptable particularly if the specification document will be public eventually, but are discouraged. For other documents, the Designated Expert will need use their judgement, or consult the OPSAWG or an Area Director.¶
Linktypes may be allocated for specifications not publicly available may be made within the FCFS range. This includes specifications that might be classified. The minimal requirement is to provide a contact person for that link type.¶
This document describes the IANA registration rules for the LINKTYPE encapsulations. PCAP-related packet file formats use this value to determine what kind of headers precede network packet captures. Many of these formats can contain IPv4 and IPv6 packets. A system reading PCAP-related format captures can be subject to arbitrary inputs that may be controlled by malicious entities, so utmost caution is required.¶
Many LINKTYPE formats include a "snapshot" length, which may be smaller than the actual packet. It is therefore very likely that trailing parts of a packet capture may be omitted, yet internal length fields in the packets will claim the packet is bigger than the capture. This leads to trivial buffer overreads, and systems interpreting the packets need to carefully scrutinize all attempts to read data from a capture.¶
PCAP has been developed over three and half decades by a variety of developers, including: Bill Fenner, Denis Ovsienko, Francois-Xavier Le Bail, Fulvio Risso, Gerald Combs, Gianluca Varenni, Gisle Vanem, Hannes Gredler, Joerg Mayer, Michal Sekletar, Stephen Donnelly, Torsten Landschoff, and Jun-ichiro itojun Hagino.¶
PCAP was originally created at LBL by Steve McCanne, Craig Leres, and Van Jacobson.¶
The authors wish to thank: Michael Tuexen, Mohamed Boucadair, Carsten Bormann, Henk Birkholtz, and Robert Wilton their invaluable comments and encouragement.¶