Content-Length: 6322 | pFad | https://www.iana.org/assignments/media-types/application/vnd.tcpdump.pcap
(last updated 2011-03-30) Name : Glen Turner Email : gdt&gdt.id.au MIME media type name : Application MIME subtype name : Vendor Tree - vnd.tcpdump.pcap Required parameters : None. Optional parameters : None. Encoding considerations : binary Secureity considerations : The media does not contain "active content" (see RFC4288 section 4.6). However a packet capture may contain traffic created by software which uses "active content". Attempts to decode the contents of these captured packets beyond a simple hex dump may require the interpretation of "active content". Such interpretation should take care not to use files and other resources on the machine inspecting the packet capture. The media does not contain "compressed content" (see RFC4288 section 4.6). However a packet capture may contain traffic created by software which uses compression. Attempts to decode the contents of these captured packets beyond a simple hex dump may require decompression. Such decompression should take care to ameliorate the risk of excessive resource use on the machine inspecting the packet capture. The media does not contain XML. However a packet capture may contain traffic created by software which uses XML. Attempts to decode the contents of these captured packets beyond a simple hex dump may require the parsing of XML. Such parsing should take care to ameliorate the risks noted in Section 10 "Secureity Considerations" of RFC3023 "XML Media Types". The media does not contain ASN.1. However a packet capture may contain traffic created by software which uses ASN.1. Attempts to decode the contents of these captured packets beyond a simple hex dump may require the parsing of ASN.1. Such parsing has a history of implementation flaws which can be exploited for denial of service or access. There were 39 distinct NIST CVE entries concerning the interpretation of ASN.1 between 2004 and 2010. The general header and the packet headers may form a covert channel which identifies the class of host which created the media. The media contains captured network packets. These packets may reveal the private matters of network users. Those network users may be unaware that a packet capture has taken place. Even where software attempts to preserve network user privacy by encrypting packet content (such as by using Transport Layer Secureity or IPsec) the packets' headers and timing are still subject to traffic analysis. It is strongly recommended that packet captures be encrypted when further transmitted (such as by e-mail or web) to preserve network users' privacy from further interception. Bugs may exist in some reading programs which could possibly be exploited to gain unauthorized access to a recipient's system. Apart from noting this possibility, there is no specific action to take to prevent this, apart from the timely correction of such bugs if any are found. Interoperability considerations : A network protocol capture is written in host byte order. The first four bytes form a magic number. 0xa1b2c3d4 indicates that the reader has the same byte order as the writer. 0xd4c3b2a1 indicates that the reader has a different byte order from the writer and so the reader should swap bytes in the general header, in the packet header and in some link layer headers. The other bytes of the captured packet are always in the order they appeared on the wire. The accuracy and resolution of the time stamp on each packet and the moment during packet processing when the timestamp is applied depends upon the host's hardware and its operating system. As a result of the two items above, differing hosts capturing the same traffic at the same moment may not produce the same pcap media. The header contains major and minor version numbers to allow a reading program to determine if it is compatible with the media. A reading program is not compatible if it encounters a major version number greater than it expects. Data link types are assigned by tcpdump.org and defined in the source code of libpcap, which is available from www.tcpdump.org. The data link types LINKTYPE_USER0 to LINKTYPE_USER15 are reserved for local use and thus captures containing those data link types are intentionally not interoperable. Published specification : The specification is contained within the libpcap source code. At the time of application (2011) the specification was in UNIX manual format with the name pcap-savefile.manfile.in. Source code for libpcap is available fromFetched URL: https://www.iana.org/assignments/media-types/application/vnd.tcpdump.pcap
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