Author(s)

Simon Tembo, Ken-ichi Yukimatsu, Shohei Kamamura, Takashi Miyamura, Kohei Shiomoto, Atsushi Hiramatsu

Department of Computer Science and Engineering, Akita University, Akita City, Japan.
NTT Network Service Systems Laboratories, NTT Corporation, Tokyo, Japan.

Shutting down a link for the purposes of a scheduled routine maintenance does cause the forwarding path to change. If these changes are not done in a required order will cause not only transient micro loops but also an overload in some links. Currently, some ISP operators use a graceful link shutdown procedure by first setting up the Interior Gateway Protocol (IGP) link metric to MAX_METRIC -1 and then shutdown the link. In this paper, we present a Pythagorean Triple Metric Sequence as a method to use to shutdown a link during such network operations. Conducting a link shutdown of any desired link for maintenance purpose is a very delicate duty that requires extreme care to prevent transient loops during such topological changes. We thus wish to demonstrate that there exists a Pythagorean Triple Metric Sequence for any given link that can be used to shutdown a link during the routine maintenance by ISPs.

MAX_METRIC; Link Shutdown; Pythagorean Triple Metric Sequence; Target Metric; Forwarding Path; Planned Failures

S. Tembo, K. Yukimatsu, S. Kamamura, T. Miyamura, K. Shiomoto and A. Hiramatsu, "Usage of Pythagorean Triple Sequence in OSPF," Communications and Network, Vol. 4 No. 1, 2012, pp. 73-82. doi: 10.4236/cn.2012.41010.