The present invention employs in-band signaling between PTEs to provision and control session keys, which are used by the PTEs for encrypting and decrypting traffic that is carried from one PTE to another over a transport network. In operation, a first PTE will receive incoming traffic from a first edge network, map the traffic to frames, encrypt the traffic with a session key, and send the frames with the encrypted traffic over the transport network to a second PTE. The second PTE will extract the encrypted traffic from the frames, decrypt the encrypted traffic with a session key, and send the recovered traffic over a second edge network toward an intended destination. If symmetric encryption is employed, the session key used by the first PTE to encrypt the traffic will be identical to the session key used by the second PTE to decrypt the traffic.