 flow 3 File transfer (25%) Input flow 4 Figure 3.3-3 Class-based queuing. CHAPTER 3.3 VolP Technology provide a barrier against unauthorized intrusion as well as ends up in the burst range when the router processes it. perform the security features needed for a VPN session. However, the method is certainly worth trying. The encryption process can take from less than 1 mil- One good piece of knowledge is that most IXCs lisecond to 1 second or more, at each end. Obviously, convert the long-haul delivery of frame relay into ATM. VPNs can represent a significant source of delay and, That is, the frame relay PVC is converted to an ATM therefore, negatively affect voice performance. Also, as PVC at the first frame relay switch after leaving the most VPN traffic runs over the Internet and there is customer's premise. It is not converted back to frame little control over QoS parameters for traffic crossing relay until the last frame relay switch before entering the the Internet, voice quality may suffer due to excessive customer's premise. This has significance because ATM packet loss, delay, and jitter. Users may be able to has built-in CoS. A customer can contract with a carrier negotiate a SLA with the VPN provider to guarantee an to convert the frame relay PVC into a Constant Bit Rate acceptable level of service. (CBR) ATM PVC. ATM CBR cells are delivered with lower latency and higher reliability. As a final note, the reader should understand that Frame relay under the best circumstances, frame relay is still inherently more susceptible to delay than ATM or TDM. The obstacle in running VoIP over frame relay involves Therefore, after applying the best possible queuing the treatment of traffic within the Committed In- mechanism, one should still expect more delay over formation Rate (CIR) and outside of CIR, commonly frame relay than would be present over ATM or TDM. termed the "burst range." Traffic up to the CIR is guaranteed while traffic beyond the CIR typically is not. This is how frame relay is Network address t