Crowd Control

Crowd control is handling of one or more links on pulls or aggressive monster pops in both exp parties and special situation like Dynamis. The idea is to neutralize all but one monster so the party or alliance only has to deal with one battle target at a time. Or, at the very least, buy enough time to exit the zone safely via Escape or running across the zone line.

Immobilize
Most often, this is done by immobilizing the extra monster(s) with various versions of Sleep, Sleepga, Lullaby, and sometimes using Shadowbind, Bind, Nightmare, or even Sleep Bolt. This method is popular in EXP parties and Dynamis.

Kiting
Another method is to kite the monster(s) using characters with high evasion or defense, or some other methods to avoid taking massive damage. This is often used in conjunction with Utsusemi, Flee, Bind, and Gravity, and sometimes Charm. This method is popular for some special mission (such as Promathia Mission 2-5) fights and HNM battles.

Tempoary Tank
Since melees generally have stronger armor than mages and often have Warrior as subjob, they can use Provoke on the extra monster, while keep attacking the current battle target. While usually not the best solution, it is often used by EXP party as a stop gag measure until mages or Bard can (re)neutralize the extra monster.

One variation would be Paladin tanking two monsters at once by tossing an extra Provoke or Flash at the second monster. A Thief also can single handily hold off a variety of monster with a combination of Sleep Bolt and Utsusemi as well. For these two alternatives, it may not be necessary to use Sleep or Lullaby.

Alternatives
A Summoner also have the option to use Astral Flow to kill the link or pop, or use an avatar to stall the extra monster. Beastmaster and Puppetmaster can use a pet or Automation to distract the monster as well. Beastmaster can also attempt Charm, as could high level Bard using Maiden's Virelai--but both are extremely dangerous on monsters typically hunted by exp parties.