An attacker can leverage the generation of IPv6 atomic fragments to trigger the use of fragmentation in an arbitrary IPv6 flow (in scenarios in which actual fragmentation of packets is not needed) and can subsequently perform any type of fragmentation-based attack against legacy IPv6 nodes that do not implement [RFC6946].
To give you an example of a fragmentation let's consider the following two networks: it should also work the same with an IPv6 since only the addressing scheme IPv6 and Fragmentation. When it came time to think about the design of what was to become IPv6 the forward fragmentation approach was considered to be a liability, and while it was not possible to completely ditch IP packet fragmentation in IPv6, there was a strong desire to redefine its behaviour. Removed in IPv6 because fragmentation is handled differently in IPv6. Flags (3-bit) — Removed in IPv6 because fragmentation is handled differently in IPv6. Fragment offset (13-bit) — Removed in IPv6 because fragmentation is handled differently in IPv6. Time to live (8-bit) Hop limit (8-bit) Same function for both headers. Fragmentation Testing and Performance: IPv4b uses normal sending and forwarding routes for the fragmentation processes. IPv6 uses the sending process only to implement and enhance the fragmentation process. Mobility Performance: It implements the basic constrained network topologies.
IPv6 Operations Working Group (v6ops) F. Gont Internet-Draft SI6 Networks Intended status: Informational N. Hilliard Expires: January 26, 2021 INEX G. Doering SpaceNet AG W. Kumari Google G. Huston APNIC July 25, 2020 Operational Implications of IPv6 Packets with Extension Headers draft-gont-v6ops-ipv6-ehs-packet-drops-04 Abstract This document
IPv6 and Fragmentation When it came time to think about the design of what was to become IPv6, the forward fragmentation approach was considered to be a liability. And while it was not possible to completely ditch IP packet fragmentation in IPv6, there was a strong desire to redefine its behaviour. IPv6 doesn't allow routers to fragment packets; however, end-nodes mayinsert an IPv6 fragmentation header1. As RFC 5722 states2, one of the problems with fragmentation is that it tends to create security holes. Although originators may produce fragmented packets, IPv6 routers do not have the option to fragment further. Instead, network equipment is required to deliver any IPv6 packets or packet fragments smaller than or equal to 1280 bytes and IPv6 hosts are required to determine the optimal MTU through Path MTU Discovery before sending packets. 1- Is this the reason of why IPsec pre-fragmentation feature can't be supported for IPv6, and the fragmentation by the IPv6 packet sender before IPsec encryption doesn't considered as pre-fragmentation because the fragmentation doesn't done by the IPsec encapsulator before encapsulation?
Aug 29, 2017 · The IPv6 specification requires that a conformant IP network path be capable of passing an IPv6 packet of up to 1,280 bytes without requiring packet fragmentation. What it fails to specify is the minimum fragmented packet size that an end host can receive.
IPv6 chooses this latter option, relying on Path MTU (PMTU) discovery to find the minimum MTU along a path (assuming PMTU actually works, a fairly bad assumption in large public networks), and allowing the IPv6 process at A to fragment information from upper layer protocols into multiple packets, which is then reassembled into the original The fragmentation offset value for the first fragment is always 0. The field is 13 bits wide, so the offset can be from 0 to 8191. Fragments are specified in units of 8 bytes, which is why fragment length must be a multiple of 8. Let us take an example to understand the calculation for fragmentation offset: Jan 08, 2019 · During fragmentation, an additional 20-byte IPv4 header is added for the second fragment, resulting in a 1500-byte fragment and a 72-byte IPv4 fragment. The IPv4sec tunnel peer router receives the fragments, strips off the additional IPv4 header and coalesces the IPv4 fragments back into the original IPv4sec packet. Aug 04, 2017 · IPv6 uses end-to-end fragmentation while IPv4 requires an intermediate router to fragment any datagram that is too large. Header length of IPv4 is 20 bytes. In contrast, header length of IPv6 is 40 bytes. IPv4 uses checksum field in the header format for handling error checking. The IPv6 specification requires that a conformant IP network path be capable of passing an IPv6 packet of up to 1,280 bytes without requiring packet fragmentation. What it fails to specify is the minimum fragmented packet size that an end host can receive. Feb 02, 2015 · IP fragmentation concepts and TTL value concepts along with verification detail in English on CISCO Gear by Aditya Gaur. IPv4/IPv6 fragmentation, TTL concepts & verification CCNP 300-101 (V-72) The Fragment header is used by an IPv6 source to send a packet larger than would fit in the path MTU to its destination. (Note: unlike IPv4, fragmentation in IPv6 is performed only by source nodes, not by routers along a packet's delivery path -- see section 5.)