Abstract: A communications system comprises a first network node coupled to a second network node so as to support a first main channel and a second main channel. A communications apparatus is coupled in-line between the first and second network nodes to support a first sub-channel in the first main channel and second sub-channel in the second main channel. The communications apparatus is arranged to determine whether an alternative sub-channel to the first sub-channel is required. If required, the communications apparatus selects the second sub-channel as the alternative sub-channel for communicating the sub-channel data.

Abstract: A communications apparatus includes an input for receiving a data stream being transmitted from a first network node to a second network node using a main channel. A processing resource of the communications apparatus identifies data signifying an idle period within the data stream and determines whether the idle period is at least a suitable minimum duration to support initiating transmission of sub-channel data in place of at least part of the data signifying the idle period. Further, the processing resource is arranged to identify when the idle period is not of the suitable minimum duration and a need arises to transmit the sub-channel data within a predetermined period of time. In such circumstances, the processing resource sends a flow control message upstream to the first network node to halt transmissions therefrom, thereby generating the idle period of at least the suitable minimum duration.

Abstract: A communications apparatus is capable of being disposed in-line in a communications link that supports a main communications channel. The communications link connects a first host to a second host. The communications apparatus comprises an application logic that supports a sub-channel within the main channel. When the main channel is potentially faulty, the application logic is arranged to monitor the main channel to determine an error condition and send a message by replacing data reserved for control purposes in order to communicate the error condition as sub-channel data.

Abstract: A system and method for measuring network performance include a first element in a network, the first element operable to receive a data packet and to create a clone packet based on the data packet, the clone packet having a destination the same as a destination of the data packet and having information identifying the clone packet as a clone, the first element operable to insert the clone packet into a data stream with the data packet.

Abstract: Arbitrary numerical distributions are presented for use in devices having limited processing and storage capabilities by having the device accept strings of arbitrarily distributed numbers from a source outside of the device. In one embodiment, a master controller creates a table of values which follow the desired minimum, maximum, mean, and standard deviation, etc. of the particular desired statistical distribution required. The created table is then communicated to the limited capacity device and can be used whenever a distribution of random values is required. The master controller could have one of several slave devices associated with it in the system. In another embodiment, where the storage capability of the device is large enough to store a table of values with sufficient different entries to create a distribution of satisfactory “randomness” for the particular application, a random number generator within the device is used to select the order of presentation of the table of values.

Abstract: By equipping receiving devices in a network with synchronizable clocks it is possible to periodically send an “impulse” signal that is received by all of the clocks at the same (or relatively the same) instant of time. The accuracy of the impulse clock need not be high, only that its signal reach all the clocks approximately at the same time. In one embodiment, a transmitting device, upon receipt of the synchronizing impulse signal, sends a packet of data bearing the sending device's epoch time-stamp to a receiving device. The data packet makes its way through the network element to the receiving device and the time-stamp is used by the receiving device to calculate the difference between the epoch time of the receiver and the epoch time of the sender. Effectively, this procedure removes the unknown network element transit times from the equation and allows the devices to operate in a synchronized manner.

Abstract: An in-line network simulator is provided that disrupts packets traveling through it to simulate network conditions. According to one embodiment, a method comprises receiving, at an in-line network simulator, packets sent from a source node to a destination node. The in-line network simulator classifies the received packets into respective ones of a plurality of different classifications, and disrupts the received packets based on corresponding disruption characteristics defined for their respective classifications. Such disrupting of the packets may include selectively performing at least one of delaying, dropping, and reordering of the received packets.

Abstract: A system for distributing digital content over a computer network (e.g., the Internet) uses certificates to establish a trust relationship between a content provider and a display device. The certificates identify the display device and the content provider as well as unique characteristics of the distribution. For example, the content provider may be a book publisher and the display device may be a printer/binder.

Abstract: Packet tracing in switched packet networks. Tracing of live packet data in a network is performed by discovering the measurement path, setting up dynamic filters along the path to collect traffic information, and collecting data as detected by the dynamic filters. Collected data is sent to a measuring entity. Filter setup may be repeated to capture data as routing changes.

Abstract: Creating a low-bandwidth channel in a high-bandwidth channel. By taking advantage of extra bandwidth in a high-bandwidth channel, a low-bandwidth channel is created by inserting extra packets. When an inter-packet gap of the proper duration is detected, the extra packet is inserted and any incoming packets on the high-bandwidth channel are stored in an elastic buffer. Observing inter-packet gaps, minimal latency is introduced in the high-bandwidth channel when there is no extra packet in the process of being sent, and the effects of sending a packet on the low-bandwidth channel are absorbed and distributed among other passing traffic.

Abstract: Discovering routing policies in information networks. Large networks such as Autonomous Systems are abstracted as a single network element. A plurality of taps on the borders of the abstracted element filter ingress/egress data which is forwarded for collection and correlation. By correlating information from different taps, routing policies are discovered. These discovered policies may be compared with published policies. Access control makes discovered policies and the comparisons with published policies selectively available depending on predefined access classes.

Abstract: A routing monitor is disclosed comprising at least one communication tap, wherein each of the at least one communication taps is positioned in a line of communication between two routers and a protocol emulator for reassembling routing protocol messages captured by the at least one communication tap and opening a routing protocol connection with a network device using the reassembled routing protocol messages in response to a request for connection received from the network device.

Abstract: An operating environment for use on a computer system to provide operating system services to a user application running on the computer system. The computer system includes a network connecting the computer system to at least one other computer system. The user application generates operating system commands requiring access to the network, and commands requiring operating system actions that do not access the network. An operating environment according to the present invention includes a network server for accessing the network, a non-network server for executing operating system commands not requiring network services, and an emulation library for receiving the operating system commands generated by the user application.