Network interface device, method and article of manufacture for providing high bit rate access over robbed bit

• US 6,178,185 B1
• Filed: 11/25/1997
• Issued: 01/23/2001
• Est. Priority Date: 11/25/1997
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Marks, Laurence Victor
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): Nguyen, Danny
• Application Number:
  US08/978,298
• Time in Patent Office: 1,155 Days
• Field of Search: 370/523, 370/522, 370/524, 370/503, 370/510, 370/514, 370/242, 370/243, 370/244, 379/251, 379/509
• US Class Current: 370/514
• CPC Class Codes: H04J 3/125 One of the channel pulses or the synchronisation pulse is also used for transmitting monitoring or supervisory signals
• CPC Class Codes: H04Q 11/0435 Details
• CPC Class Codes: H04Q 2213/13176 Common channel signaling, CCS7
• CPC Class Codes: H04Q 2213/13199 Modem, modulation
• CPC Class Codes: H04Q 2213/13202 Network termination [NT]
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/13213 Counting, timing circuits
• CPC Class Codes: H04Q 2213/13214 Clock signals
• CPC Class Codes: H04Q 2213/13215 Code checking, CRC
• CPC Class Codes: H04Q 2213/13216 Code signals, frame structure
• CPC Class Codes: H04Q 2213/13292 Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13305 Transistors, semiconductors in general
• CPC Class Codes: H04Q 2213/1332 Logic circuits
• CPC Class Codes: H04Q 2213/13322 Integrated circuits

Abstract

A method, apparatus and article of manufacture are described. In particular two network interface devices that are connected over a path that includes a digital trunk using robbed-bit signaling use a technique to identify the presence of robbed-bit signaling. The network interface devices synchronize to bytes that are subject to robbed-bit signaling. The network interface devices must synchronize to the robbed-bit signaling to avoid transmitting information or receiving information in these signaling positions. The network interface devices then take advantage of the least significant bit positions of frames that are not used for robbed-bit signaling. This results in an increase in data carrying capacity from 56 kps to 62.7 kps.

Claims

1. A method of operating a network interface device comprising the steps of:

generating a repeating sequence of values, advancing the sequence with every outbound frame;

sending a test pattern over a network connection, each frame of the test pattern including a synchronization value representing the sequence value or an indication of the position of the sequence value within the sequence and at least one bit for determining which frames are affected by robbed bit signaling;

receiving a message containing zero, one or more synchronization values; and

,

sending data over the connection in a seven bit payload frame when the repeating sequence corresponds to one of the stored synchronization values, otherwise sending data using an eight bit payload frame.

2. The method of claim 1 further comprising the steps of:

receiving connection type information from the connection;

tailoring the test pattern using the connection type information.

3. A method of operating a network interface device, comprising the steps of:

generating a repeating sequence of values, advancing the sequence with every inbound frame;

receiving a test pattern from a network connection;

synchronizing the repeating sequence using the received test pattern;

detecting which frames of the received test pattern contain robbed-bit signaling, storing the synchronization value of each frame in which robbed-bit signaling is detected,

sending the stored synchronization values;

receiving data from the connection and discarding a LSB from the received frame whenever the repeating sequence corresponds to one of the stored synchronization values.

4. A network interface device comprising:

an network interface adapted for providing access to a network, the network interface adapted for establishing a connection;

a sequence generator for generating a repeating sequence, the sequence advancing with every outbound frame;

a transmitter for transmitting a test pattern over the frame aligned connection, each frame of the test pattern including a synchronization value representing the sequence value or an indication of the position of the sequence value within the sequence and at least one bit for determining which frames are affected by robbed bit signaling;

a receiver for receiving a synchronization message, the synchronization message including zero, one or more synchronization values;

wherein user data is transmitted using a seven bit payload frame when the repeating sequence corresponds to one of the received synchronization values;

otherwise transmitting user data using an eight bit payload frame.

5. The network interface device of claim 4 further including:

a host interface for receiving a user data stream;

an encoder for encoding the user data stream into an output data stream;

a counter which is synchronized to the occurrence of robbed-bits in an output stream.

6. The network interface device of claim 5 wherein the sequence generator is a modulo N counter.

7. The network interface device of claim 6 wherein the synchronization values are counter values generated by the modulo N counter.

8. The network interface device of claim 6 wherein the synchronization values are obtained using the counter values generated by the modulo N counter to access a table wherein the accessed table entries are used as the synchronization values.

9. A network interface device comprising:

an network interface adapted for providing access to a network, the network interface adapted for establishing a connection;

a sequence generator for generating a repeating sequence, the sequence advancing with every inbound frame;

a receiver for receiving a test pattern, each frame of the test pattern having a synchronization value representing the sequence value or an indication of the position of the sequence value within the sequence and at least one bit for determining which frames are affected by robbed bit signaling;

a synchronizer for synchronizing the sequence generator using the received test pattern;

detecting which frames of the test pattern were affected by robbed bit signaling, storing the synchronization values of each frame in which robbed-bit signaling is detected,

a transmitter for transmitting the synchronization values; and

wherein user data is received by discarding a LSB from the received frame whenever the repeating sequence corresponds to one of the stored synchronization values.

10. The network interface device of claim 9 further including:

a host interface for receiving a user data stream;

an encoder for encoding the user data stream into an output data stream;

a counter which is synchronized to the occurrence of robbed-bits in an output stream.

11. A method of operating a network interface device comprising the steps of:

establishing a connection to first destination through a network;

requesting the highest possible bit rate communication;

sending a test pattern, the test pattern designed to determine if robbed-bit signaling is utilized on the connection;

receiving a notification indicating if robbed-bit signaling was detected by the first destination and in which positions of the test pattern;

starting a counter that synchronizes the sending of data with the robbed-bit signaling, if robbed-bit signaling is detected; and

,

transmitting data stream using eight bits of a byte format, unless the counter indicates that a robbed-bit position is present in which case information is transmitted using the 7 most significant bits of an eight bit byte format with the least significant bit position unused reserved for robbed-bit sampling.

12. A method of operating a network interface device comprising the steps of:

accepting a connection to first destination through a network;

exchanging capability information requesting the highest possible bit rate communication including an indication that the first destination is digitally connected;

receiving a test pattern, the test pattern designed to determine if robbed-bit signaling is utilized on the connection;

determining from the test pattern wether robbed-bit signaling is present and at which positions of the test pattern;

sending a notification indicating if robbed-bit signaling was detected and in which positions of the test pattern using a clock derived from the received test pattern;

starting a counter that synchronizes the reception of data with the robbed-bit signaling on the connection, if robbed-bit signaling is detected; and

,

receiving information in all eight bits of a byte format, unless the counter indicates that a robbed-bit position is present in which case information is received from the 7 most significant bits of an eight bit byte format with the least significant bit position ignored.

13. An article of manufacture comprising a processor useable medium having a processor readable program embodied in said medium, wherein the processor readable program when executed on a processor causes the processor to:

generate a repeating sequence of values, advancing the sequence with every outbound frame;

send a test pattern over a network connection, each frame of the test pattern including a synchronization value representing the sequence value or an indication of the position of the sequence value within the sequence and at least one bit for determining which frames are affected by robbed bit signaling;

receive a message containing zero, one or more synchronization values; and

,

send data over the connection in a seven bit payload frame when the repeating sequence corresponds to one of the stored synchronization values, otherwise sending data using an eight bit payload frame.

14. The article of manufacture of claim 13, wherein the processor readable program when executed on a processor causes the processor to:

receive connection type information from the connection;

tailor the test pattern using the connection type information.

15. An article of manufacture comprising a processor useable medium having a processor readable program embodied in said medium, wherein the processor readable program when executed on a processor causes the processor to:

generate a repeating sequence of values, advancing the sequence with every inbound frame;

receive a test pattern from a network connection;

synchronize the repeating sequence using the received test pattern;

detect which frames of the received test pattern contain robbed-bit signaling, storing the synchronization value of each frame in which robbed-bit signaling is detected,

send the stored synchronization values;

receive data from the connection and discarding a LSB from the received frame whenever the repeating sequence corresponds to one of the stored synchronization values.