OSPF WG Stronger, Automatic Integrity Checks for OSPF Packets Paul Jakma, University of Glasgow Manav Bhatia, Alcatel-Lucent IETF 79, Beijing

Introduction (1/2) OSPF currently uses standard internet checksum to detect corruption Internet checksum is known to have weaknesses - cannot detect reordered bits, certain patterns of bit flips, etc Some operators use cryptographic authentication (MD5 or something stronger) to detect such errors

Introduction (2/2) Using crypto is not good as it requires more computation, which may be noticeable on less powerful and/or energy sensitive platforms Operators need to configure the keying material on all routers which is an additional administrative burden

Proposed Mechanism for OSPFv2 Data field in case of NULL Authentication is ignored This document overloads that field to indicate the new checksum algorithm that receivers must use Checksum data is carried similar to how OSPFv2 auth data is carried

Proposed Mechanism for OSPFv3 Uses new EC-bit (Extended Checksum) in OSPFv3 Options field Defines a new Extended Checksum data block that will carry both the details of checksum algorithm being used and the checksum data for the receiving end to verify

Extended Checksum in OSPFv2 and OSPFv3 IPv6 Header - Length = HL + X + Y OSPFv3 Header Length = X OSPFv3 Protocol Data Extended Checksum Data X Y IP Header - Length = HL + X + Y OSPF Header Length = X OSPFv2 Protocol Data Extended Checksum Data X Y NULL Authentication Length = Y Checksum Type Extended Checksum Length = Y

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