Well, its a very known PvP spec for Mage in the latest version since Frost is a crit-machine spec with better survivability. Its a deep Frost with a bit of Arcane on it to improve more burst damage on Frostbolt from Torment the Weak. Frost with Arcane can also provide more Armor bonus from Arcane Fortitude based on your Intellect. More of Arcane's benefits on frost is Improved Counterspell, Magic Attunement, Spell Impact and Magic Absorption.
Frostcane Fire Spec
A rather DoT-Freeze Spec, which is kinda similar to Frost-Arcane spec but whats different is it has fire on it. Since most skilled mages usually use Fire Blast, its very essential especially when you use it to a target affected by Frost Nova because of the fact that it can do 100% Crit with Shatter and that Ignite procs which is very useful against Vanish skill for rogues. Another thing for a fire mage is the Impact, which stuns the target for 2 seconds and it procs on all spells.