From e386597bc7dff2982deadbc53c6a7d0d2b8e9921 Mon Sep 17 00:00:00 2001 From: Michael Richardson Date: Mon, 12 Aug 2024 08:17:55 -0400 Subject: [PATCH] added text explaining relationship between documents --- draft-ietf-opsawg-pcap.md | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/draft-ietf-opsawg-pcap.md b/draft-ietf-opsawg-pcap.md index 388c9bd..b6033ba 100644 --- a/draft-ietf-opsawg-pcap.md +++ b/draft-ietf-opsawg-pcap.md @@ -55,8 +55,19 @@ 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. -This document describes the format used by tcpdump, and other +This document describes the historical format used by tcpdump, and other programs using libpcap, to read and write network traces. +This document describes version 2 of the pcap format. + +This document is published as historical, as there has existed for some time, an updated format originally called "pcapng", that replaces this file format. See {{?I-D.ietf-opsawg-pcapng}} +No new extensions for this format are expected, although new LINKLAYER types that are registed using {{!I-D.ietf.opsawg-pcaplinktype}} can be included in pcap files. + +A major limitation of the pcap v2 format described here is that files consist of a header which is different than the other blocks in the file. +This prevents pcap v2 files from being simply concatenated for processing. +It is also difficult to break pcap v2 files apart, as a new header always needs to be placed at the beginning of any new file. The pcapng format does not suffer from these problems. + +More significantly, pcap v2 files can only contain packets in a single LINKTYPE format, and this often means that packets are often from a single network interface as not all LINKTYPEs include a way to indicate which interface a packet is from. + # Terminology