Some years ago I saw a referee dealing with a fight in a Senior club rugby match between University and High School Oldboys, a bitter rivalry if ever there was one.
This was in the days before coloured cards, the referee was a well known member of the CRRA, Alan Taylor. His way of dealing with it was to blow his whistle several times, and if they ignored him, he just stood aside and watched the fight. Alan was one of those unique individuals with the ability to recall a sequence of events accurately and in detail. After a game, he could tell you which players scored which tries, and how they did it, and what he gave all the penalties and scrums for, and where where on the field goals were kicked from.
On this occasion, he was watching and noting every swing, every punch aver act of pushing and shoving, and what is more important, the jersey number of every player involved.
When the stouch petered out, he called the two Captains, over, and there he began to give a calm and dispassionate detailed account of what had happened, and as he did so, players were called over one by one and marched off the field. When Alan had finished, the two players who started the fight (the initial puncher and the retaliator) were sent off, and another half-dozen players (roughly evenly distributed between the sides) ended up in the cooler (sin bin).
It was comical watching a procession of players to their own dead-ball lines (thats where we used to send binned players)
The rest of the game went without incident, as he also gave a final warning to both sides.