Viper’s Router Functionality
Beyond simple Point-to-Point and Point-to-Multipoint capabilities, Viper can be configured to act as a wireless repeater, a wireless bridge, or as a wireless router. As a repeater, the Viper will accept incoming traffic and retransmit it without change. This effectively extends the range of a wireless network. As a bridge, Viper will perform a similar retransmission function, with the additional capability to accept incoming transmissions using one protocol, and retransmit them using a different protocol. Finally, Viper can act as a highly sophisticated router, in which the retransmission of the incoming signal can be performed selectively to different target destinations, based an a variety of criteria. Among other things, Viper’s router functionality permits the creation of dynamic multi-hop Store and Forward network topologies.
Viper’s routing capabilities are impressive and unmatched by our competitors. Collectively, they provide the network operator with tremendous flexibility in designing, configuring, and operating robust, dynamic networks.
When functioning as a router, Viper is able to detect, initiate, and maintain communications with neighboring radios in an automated fashion. In addition to manual configuration, Viper is equipped with a powerful neighbor discovery capability, which enables the automatic discovery of all Viper units in the RF network, and the associated configuration of all the necessary IP routes to reach these neighboring units automatically. Viper accomplishes this with a separate set of control messages. Viper uses Routing Internet Protocol Version 2 (RIP v2), which is responsible for passing router information to other routers in the network.
Advanced Networking Capabilities
Viper exceeds the capabilities of competitive radios by offering true router functionality. As such, Viper offers numerous features for detecting RF traffic, Network Address Translation (NAT) and port mapping for packet transmission.
RF environments are inherently variable. Weather, terrain, and RF interference all can conspire to reduce the quality of the RF environment, rendering transmissions less reliable. Viper offers the ability to enable an acknowledgement protocol that is designed to verify the successful transmission of each unicast data packet. This is extremely useful for IP optimization and tuning. When enabled, Viper will reply with a short acknowledgment upon the successful reception of a packet. This adds a small amount of latency to each packet, but it helps to diagnose a failed remote unit quickly, and keep overall network throughput high by eliminating bandwidth waste that arises from ongoing attempts to communicate with a failed unit.
Managing Over-the-Air Traffic
Viper uses a variety of techniques to establish, maintain, and verify wireless data transmission, including techniques for transmission retries, collision avoidance, and a technique known as random backoff.
Contention management can be useful in maximizing overall network throughput in larger, more active networks where several Vipers are likely to compete for airtime. In these networks, it is more likely that several radios will compete for airtime after a transmission has completed and the channel becomes available. In order to reduce the possibility of a collision - a situation in which more than one radio transmits simultaneously - Viper can randomly select a waiting period (defined as a specific number of time slots) to wait before attempting to acquire the channel and transmit. This functionality is referred to as Random Backoff. With each Viper in the network waiting a random period of time, the likelihood the collisions is substantially reduced.
Viper’s Collision Avoidance is a handshaking technique that is designed to avoid simultaneous transmission from multiple radios. In return for a small amount of additional latency, Viper can be configured to transmit a short two-way handshake that informs other Vipers in the network that a transmission is about to take place. These other remote radios can then wait until the channel becomes available. This feature is particularly useful when remote Vipers are located at sites where the terrain prevents them from monitoring each other’s transmissions. This method of collision avoidance is sometimes referred to as “polite” radio mode.
By definition, when a Viper is configured as a router, it is configured to communicate with more than one remote radio. Each of these connections is likely to exhibit somewhat different link characteristics, because of attenuation from natural obstacles in the signal path, and differences in distance, terrain, and the overall signal environment. These variations may be large or small, and accordingly the communications link can be stronger or weaker.
Viper can be configured to vary the over-the-air data rate to a remote radio on a per-link basis. Links with strong signals can be configured for high data rates. Links with poorer signal strength can be configured to use slower, but more robust data rates. This capability is referred to as Multispeed, and it permits the network operator to maximize the overall throughput and reliability of a Viper RF network by accommodating the natural variations in the RF environment that arise from the configuration of any given network.
Viper is highly secure. It uses a number of techniques to ensure that the Viper network remains impenetrable to unauthorized users, including AES Encryption, RADIUS Authentication, and Virtual Private Networking.
Viper uses Advanced Encryption Standard (AES) 256 encryption. AES 256 is a symmetric-key block cipher adopted as an encryption standard by the United States government. AES Encryption is applied to data passing through both Ethernet and serial ports. AES 256 is an extremely secure encryption standard that virtually eliminates the possibility of decryption.
Radius authentication is used by VIPER for both user authentication and device authentication. Radius provides a secure, reliable, standardized method for accessing and verifying the credentials of a request for network access.
Virtual Private Networking
Router mode on the Viper features the ability to set up a FIPS 140-compliant Virtual Private Network (VPN). VPNs are used to provide a secure connection or “tunnel” on an otherwise insecure network, such as the internet. This permits a private Viper network to use public communications networks secuely, without compromising the inherent security of a private network. Packets can be filtered to pass through the VPN with strong encryption.
Network Address Translation
When configured as a router, Viper makes use of Network Address Translation (NAT) capabilities. As such, Viper is able to manage private IP network spaces and hide them from public networks. In this capacity, Viper functions as a firewall, and all transmissions from inside the private network appear to originate from the router. That is, Viper will permit communications through the router only from addresses that originate inside the private network. NAT is a well-developed and secure method of providing architectural security for private networks. It is however, only one of the many security techniques used by Viper for security access to and use of the network.
Quality of Service
In order to understand the unique value of Viper’s Quality of Service (QoS) capabilities, it is necessary to understand why traditional implementations of QoS provide little or no value in an RF environment.
QoS in an RF network exhibits important differences from QoS in a traditional IP network. This is because landline-based networks are full duplex (data can be sent and received simultaneously on the same connection) and RF networks are half-duplex (data cannot be sent and received simultaneously). In full-duplex networks, any transmission device is likely to have a queue of incoming packets that build up at the device. Usually, these packets have been received from multiple sources, and arrive at the device more quickly than they can be retransmitted. The device responds by placing the incoming packets in a queue, which buffers the incoming traffic before it is retransmitted by the device.
Traditional QoS algorithms reorder these packets before retransmission according to rules set up in advance that give priority to one packet over another, based up any number of factors (source, destination, protocol, port, etc.). However, for this to work properly, there must be a queue of multiple packets extant on the device. In a half-duplex RF environment, the likelihood a sizable queue developing is very low, because the half-duplex nature of the transmission prevents packets from arriving from more than one source simultaneously.
Viper addresses this inherent limitation by throttling the outgoing traffic. That is, it uses QoS algorithms to reduce the over-the-air transmission speeds below the maximum RF data rate. This permits an incoming queue to develop, and allows traditional packet reordering to take place. This process is called Rate Limiting.
Viper’s QoS implementation, therefore, provides all of the traditional capabilities of a sophisticated IP QoS, plus an intelligent implementation of those capabilities in a half-duplex RF environment. This ensures that QoS will actually work as intended in a private RF network.