Billion 5100 User Guide

 

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Point-to-Point Tunneling Protocol (PPTP) is a network protocol that enables secure transfer of 

data from a remote client to a private server, creating a Virtual Private Network (VPN) using 

TCP/IP-based networks. 

PPTP supports on-demand, multi-protocol and virtual private networking over public networks, 

such as the Internet. 

Traffic Shaping is an agreement between the carrier and the subscriber to regulate the 

average rate and “burstiness” or fluctuation of data transmission over an ATM network. This 

agreement helps eliminate congestion, which is important for transmission of real time data 

such as audio and video connections. 

Peak Cell Rate (PCR) is the maximum rate at which the sender can send cells. This parameter 

may be lower (but not higher) than the maximum line speed. 1 ATM cell is 53 bytes (424 bits), 

so a maximum speed of 1 Mbps gives a maximum PCR of 2415 cells/sec. This rate is not 

guaranteed because it is dependent on the line speed. 

Sustained Cell Rate (SCR) is the mean cell rate of a bursty, on-off traffic source that can be 

sent at the peak rate, and a parameter for burst-type traffic. SCR may not be greater than the 

PCR; the system default is 0 cells/sec. 

Maximum Burst Size (MBS) is the maximum number of cells that can be sent at the PCR. After 

MBS is reached, cell rates fall below SCR until cell rate averages to the SCR again. At this 

time, more cells (up to the MBS) can be sent at the PCR again. 

The following figure illustrates the relationship between PCR, SCR and MBS.