By Bryon Moyer, Teja Technologies, Inc.
Increasingly, network equipment uses packet technology to carry information. Even systems used in the basic telephony infrastructure are moving away from the traditional circuit-based approach to a packet-based approach. Such systems take an incredible volume of voice traffic and push it over the packet network by creating "pseudo-wires" that allow a phone system to think it has a circuit, when in fact it doesn't. This allows a huge amount of on-premise equipment to remain in place while the core of the system takes advantage of packet technology. Large numbers of voice channels can be aggregated together, creating significant packet traffic. Less than 1000 T1 lines add up to gigabit rates.
Aggregated packetized voice traffic, traditionally transmitted on ATM, is increasingly carried on Ethernet. A node that manages aggregated voice traffic must be able to interface between ATM-based ports (e.g., packet-over-Sonet--PoS) and IP-based ports (e.g., Ethernet) (See Figure 1). This requires an IP/ATM bridge to ensure that all voice traffic is routed onto the appropriate port, regardless of whether it starts or ends as IP or ATM.
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