Vocality V100 TCP Performance Enhancing Proxy
Vocality V100 Integrated Bridge/Router and TCP Accelerator (PEP)

The PEP option module for the V100 from Vocality International enables full utilization of available bandwidth for TCP traffic, with high rates of optimization and error handling. TCP/IP uses windowing to send and acknowledge data packets. Any unacknowledged data packets are stored in a window (buffer with a size limitation). The idea is that the window (maximum number of packets in transit) is never full as packets are acknowledged and removed from it thus enabling a continuous stream of data.

With Standard TCP

As an example: With standard TCP, the relatively large delay of a satellite link means that the window is filled before acknowledgements have been received. As a result of this, the data stream then stops. This continuous start stop process means that the link is very inefficient – around 30% maximum. If packets are not acknowledged then it is assumed that they have not been received and so they are re-sent, thus further lowering the efficiency of the link and also the throughput rate. Throwing more bandwidth at the system makes no difference. Other “terrestrial” routers also suffer greatly from high error links with dramatic drops in link efficiency. These are just two examples of why TCP throughput with regular terrestrial routers can be very low over satellite links.

With TCP Performance Enhancing Proxy

Vocality has for many years used a proprietary protocol for connecting its products together. This optimisation is a result of experience, tried and tested in the field. Vocality takes standard data and voice protocols and converts them into it's own for transmission and then re-presents them back to the user. Vocality has taken this experience, and that of working with users of its Satellite Simulator product range, to provide an optimised TCP facility which can do justice to the high levels of budget spent on international satellite links.

What About Errors?

Unlike some other optimisation systems, the Vocality TCP optimisation system gives significant throughput and speed improvements even on high error links.

Features:

Interface: 10/100 base-T

Presentation:

• IPv4 Static Router/Bridge including DHCP Server/Relay
• Spanning Tree (IEEE 802.1d) Protocol for Bridged Networks
• Optional PEP (Performance Enhancing Proxy) for TCP
• UDP Relay for IP Subnet Broadcasts
• Proxy ARP
• Telnet for IP Based Supervisor Access with Security Filtering
• Full Integration with Dynamic Bandwidth Allocation