Last revised by Ali Farshchian,
Feb 18, 06 at 7:05 pm PDT |
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Because IP does not provide any mechanism to ensure that data packets are delivered in sequential order, or provide any Quality of Service guarantees, VoIP implementations may face problems dealing with latency (especially if satellite circuits are involved), and jitter. They are faced with the problem of restructuring streams of received IP packets, which can come in any order and have packets delayed or missing, to ensure that the ensuing audio stream maintains a proper time consistency. This problem has been addressed by Ubicom with their StreamEngine Technology.
Another main challenge is routing VoIP traffic to traverse certain firewalls and NAT. Intermediary devices called Session Border Controllers (SBC) are often used to achieve this, though some proprietary systems such as Skype traverse firewall and NAT without a SBC by using users’ computers as super node servers to route other people’s calls.
Keeping packet latency acceptable can also be a problem, due to network routing time (buffering, switching) and transmission distances (more relevant under satellite links).
This text is licensed under the GNU Documentation License. It uses material from the Wikipedia article “VoIP".