Wimax standards and Security The Wimax

QoS in Circuit-Switching Network

In a circuit-switched network, each data stream has a dedicated connection (called circuit) from a source to a destination. As there is no competition from multiple data streams, the performance is determined by (a) the network device, (b) the transmission media, and (c) the distance of the transmission. There is no need for QoS in a circuit-switched network because the service is guaranteed due to the deterministic nature of the network. An example is the traditional public switched telephone network (PSTN). If a packet-switching technology emulates the circuit-switched network, known as circuit emula- tion service (CES), its performance would be guaranteed due to the nature of a circuit-switched network.

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   QoS of Packet-Switched Network
   

On a wired network, congestion occurs on the device and never happens on the media (i.e., the wired cable). For a connectionless service, the QoS information is carried on the packet itself. For a connection-oriented service, the QoS is configured on the device.

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   Connectionless Service (Ethernet or IP)
   

In a connectionless network (Ethernet or IP), each packet needs to carry the QoS information in its packet header. For Ethernet, the IEEE 802.1p standard supports a 3-bit priority scheme and it allows up to eight priority classes

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[4] while most implementations support only two queues (priority 0 and priority 0). An incoming Ethernet frame is put into one of the queues. Frames in the high-priority queue are processed first. The Internet Proto- col (IP) also allows IP packets to carry QoS information in the packet header, which is a 6-bit type of service (ToS) field. An IP-router with QoS capability has multiple queues for incoming traffic based on the ToS field. In addition, there are various protocols to support end-to-end QoS on an IP network [3].

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