| 单词 | POS |
| 释义 | POS 1. Packet Over SONET. A MAN/WAN technology that supports packet data (e.g., IP) through either a direct optical interface to a router, or through a SONET demarc in the form of a terminating multiplexer (TM). POS uses SONET as the Physical Layer protocol, encapsulating packet traffic in High-level Data Link Control (HDLC) frames and using Point-to-Point Protocol (PPP) at the Data Link Layer, with the IP packet traffic running at the Network Layer.The result is that the combined overhead factor (SONET + PPP + IP) is only approximately 5 percent for a 1,500-byte IP datagram. This level of efficiency compares very favorably with asynchronous transfer mode (ATM), which involves an overhead factor of approximately 11 percent for the same IP datagram.This level of performance can be achieved only if packet data is to be transmitted, and only if the service is provided over the equivalent of a SONET-based, point-to-point private line, provisioned in the form of a Virtual Tributary (VT). The use of a VT enables POS traffic to bypass any ATM switches that might be in place in the carrier network. See also ATM, datagram, Data Link Layer, demarc, encapsulate, HDLC, IP, MAN, Network Layer, overhead, packet, Physical Layer, point-to-point, PPP, protocol, router, TM, VT, and WAN. 2. Personal Operating Space. The area in the near vicinity of a device or individual. POS is fundamental to the concept of a wireless personal area network (WPAN). See also WPAN. |
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