2

Source: The TCP-IP Guide—A Comprehensive, Illustrated Internet Protocols Reference by Charles M. Kozierok (2005)

Example:

Note that RIP is designed so that a routing entry is replaced only if information is received about a shorter route; ties go to the incumbent, if you will. This means that once Router RD creates an entry for Network N1 with a cost of 3 going through Router RB, if it receives information that it can reach Network N1 at the same cost of 3 through Router RC, it will ignore it. Similarly, if it gets Router RC’s information first, it will ignore the information from Router RB.

This seems to be a variation on the baseball-related expression tie goes to the runner. But even after having looked it up, I'm still not one hundred percent sure if I understand what the author is trying to say there. Could you please dissect it for me bit by bit?

1
  • The metaphor is an election, I think, possibly conflated with baseball. The incumbent routing entry (the one occupying the "seat" now) is ousted only by a shorter route. Routes equal to it in length or longer than it are discarded. Apr 27 '17 at 18:44
3

You're right about the reference to baseball: if a runner touches the base at the exact instant that the baseman acquires the ball (in case of a force out), the runner is safe. (The tie goes to the runner.)

tie
6.
a. An equality of scores, votes, or performance in a contest: The election ended in a tie.
b. A contest so resulting; a draw.

This usage has obviously been expanded into the realm of metaphor here, perhaps a bit awkwardly. The incumbent means whatever entry currently occupies the spot. If one with a shorter route shows up, the incumbent is replaced. If one shows up of the same size or larger, no replacement occurs.

You can express this in pseudocode this way:

if (incumbent > entry) {
   // replace incumbent with entry
}

You can see that even if the entry is the same size as the incumbent, no replacement will take place.

4
  • I don't think that's a baseball allusion per se. The word "tie" in this sense applies to any sort of game or contest, and I've heard the phrase "ties go to ..." used in many such contexts. Yes, it applies to baseball, but it also applies to many other contests. Given the use of the political term "incumbent", I'd relate it more to politics than to baseball.
    – Jay
    Apr 27 '17 at 21:39
  • 2
    @Jay: The point is, that baseball rule is where the whole thing started, or at least was popularized.
    – Robusto
    Apr 27 '17 at 22:05
  • Did that phrase really originate with baseball rules, or is that just where you first heard it? If it really did originate with baseball, fair enough. I've heard it in many other contexts.
    – Jay
    Apr 28 '17 at 19:06
  • @Jay - It may have originated somewhere else, but baseball is definitely the first place my mind goes when I hear a variant.
    – J.R.
    May 10 '18 at 1:29

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