Behavior during OSPF premature aging
Hi, When premature aging an LSA, bird seems to increase the LSA sequence number to its maximum (proto/ospf/lsupd.c line 616, in 1.4.3). RFC 2328 14.1 (page 156) states "An LSA can be flushed from the routing domain by setting its LS age to MaxAge, while leaving its LS sequence number alone, and then reflooding the LSA." While I don’t see a valid technical reason this should break, I seem to have a device in my network which ignores this updates LSA, I suspect it is doing an unsigned int comparison instead of a signed comparison. While I think the main fault lies with the other vendor, my question at this time is: what is the reasoning behind updating the sequence number to its maximum, even though the RFC says to leave it as-is? Regards, Lennard Klein This email is from Equinix (EMEA) B.V. or one of its associated companies in the territory from where this email has been sent. This email, and any files transmitted with it, contains information which is confidential, is solely for the use of the intended recipient and may be legally privileged. If you have received this email in error, please notify the sender and delete this email immediately. Equinix (EMEA) B.V.. Registered Office: Luttenbergweg 4, 1101 EC Amsterdam-Zuidoost, The Netherlands. Registered in The Netherlands No. 57577889.
On Tue, Jun 24, 2014 at 08:46:20AM +0100, Lennard Klein wrote:
Hi,
When premature aging an LSA, bird seems to increase the LSA sequence number to its maximum (proto/ospf/lsupd.c line 616, in 1.4.3).
While I think the main fault lies with the other vendor, my question at this time is: what is the reasoning behind updating the sequence number to its maximum, even though the RFC says to leave it as-is?
Hi This is done mainly to compensate other problems/quirks/hacks in BIRD OSPF implementation. One reason is that if you flush LSA using MaxSeqNo, you could forget old LSA sequence number, and when you originate a new one later, you could safely start from InitSeqNo. Currently i am finishing OSPF revision that removes most of these BIRD quirks and problems related to LSA flood and makes BIRD much better in RFC compliance. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
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Lennard Klein -
Ondrej Zajicek