Operational Neighbor Discovery Problems and Enhancements.
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|Intended RFC status||(None)|
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In IPv4, subnets are generally small, made just large enough to cover the actual number of machines on the subnet. In contrast, the default IPv6 subnet size is a /64, a number so large it covers trillions of addresses, the overwhelming number of which will be unassigned. Consequently, simplistic implementations of Neighbor Discovery can be vulnerable to denial of service attacks whereby they attempt to perform address resolution for large numbers of unassigned addresses. Such denial of attacks can be launched intentionally (by an attacker), or result from legitimate operational tools that scan networks for inventory and other purposes. As a result of these vulnerabilities, new devices may not be able to "join" a network, it may be impossible to establish new IPv6 flows, and existing ipv6 transported flows may be interrupted. This document describes the problem in detail and suggests possible implementation improvements as well as operational mitigation techniques that can in some cases to protect against such attacks. It also discusses possible modifications to the traditional [RFC4861] neighbor discovery protocol itself.
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