The sign of Peace is not a social greeting. It is a liturgical sign and as such should be kept within the liturgy and should be exchanged with dignity and in a sober manner in such a way that it does not become a distraction.
The sign of Peace is part of the Communion Rite. It signifies that the Peace of Christ brings about not only peace itself but also unity. In this sense, it also means that the Peace of Christ brings people into union - into communion. This sign prepares the faithful to come as one community to partake of the Body and Blood of Christ.
-fr. Jorge Rátiva, O.P.