T3/E3 Datacom HDLC Protocol Analysis

Protocol Summary, Detailed, and Hexdump Views in HDLC Protocol Analysis

The HDLC analyzer application is invoked from the main menu of GL's T3/E3/Datacom Analyzer for real-time analyzer. The analyzer displays summary, detail and hex dump view in different panes. The summary pane displays Frame Number, Time, Length, Error, C/R, SAPI, TEI, CTL, P/F, N(S), N(R), FUNC etc. User can select a frame in summary view to analyze and decode each frame in the detail view. The selected frame is analyzed and decoded according to HDLC frame specifications. The Hex dump view displays the frame information in HEX and ASCII.

Port Selection for real-time capture

Users can capture and analyze multiple HDLC links in real-time and record all or filtered traffic into a trace file. The recorded trace file can then be analyzed offline and exported to ASCII file, or printed. Real-time capturing requires user to specify Tx/Rx ports FCS (16 & 32 bits).

Offline Filtering and Search Criteria for HDLC Protocol Analysis

Users can record all or filtered traffic into a trace file. Filtering and search capability adds as another powerful feature to the HDLC Analyzer. This feature can isolate required frames from all frames in real-time as well as off-line. Users can specify custom values for frame length to filter frames during real-time capture. The frames can also be filtered after completion of capture according to CTL, C/R, Modifier Function, N(R), N(S), P, P/ F, SAPI, Supervisory function and TEI. Similarly, search capability helps user to search for a particular frame based on specific search criteria.

Calculated Statistics View in HDLC Protocol Analysis

Statistics is an important feature available in HDLC analyzer and can be obtained for all frames both in real-time as well as offline mode. Numerous statistics can be obtained to study the performance and trend in the HDLC network and it is based on protocol fields and different parameters e.g. Use Type (Key/Total/Field), Statistic type (Frame count, Byte count, Frames/Sec) and patterns like Range List, Wild card etc.

Protocol Trace Saving Options for HDLC Protocol Analysis

Users can control the captured trace files by saving the trace using different conventions such as trace files with user-defined prefixes, trace file with date-time prefixes, and slider control to indicate the total number of files, file size, frame count, or time limit. This feature also allows the captured frames to be saved into a trace file based on the filtering criteria set using display filter feature

Transmit and Receive HDLC frames Test Application for T3 E3

USB T3/E3 HDLC Test Optional Application is designed to transmit and receive HDLC frames over unstructured T3/E3. It generates frames in memory and fills them with 64 bit sequential integer numbers. The number is either truncated if the frame length is less than 8 bytes or the same number bytes are concatenated to make up the complete frame

At the end of each frame a Frame Check Sequence (FCS) is generated to verify the data integrity on the receive side. The FCS (also knows and cyclic redundancy check CRC) is calculated using a polynomial.

16 bit FCS is generated using polynomial 1 + x⁵ + x¹² + x¹⁶

32 bit FCS is defined in RFC 1662 and is using polynomial x⁰ + x¹ + x² + x⁴ + x⁵ + x⁷ + x⁸ + x¹⁰ + x¹¹ + x¹² + x¹⁶ + x²² + x²³ + x²⁶ + x³²

Three types of frame length sequences are supported:

• Fixed length
• Variable length with framed data length is incremented from the minimum value to the maximum value by one and after maximum length is reached the minimum length is transmitted
• Random length in the minimum - maximum range.

User can specify the number of flags between frames to vary the data utilization.

The receiving part receives the frames and verifies if the received frames conform to the specified pattern data sequence and frame length. The following errors are counted:

• Frame errors - HDLC zero bit insertion/deletion error that are constituted by non-integral number of octets between flags
• Length errors - frame length is different from expected
• CRC errors - FCS errors
• Sequence errors - sequential 64 bit integer numbers places in the frame are out of sequence

Higher level protocol headers can be specified by user and prepended to frames.

Multiple instances of the application can run simultaneously for different ports. Each instance can be:

• Receive and transmit
• Receive only
• Transmit only

Transmit and Receive HDLC frames Test Application for Datacom

The HDLC Automated Test System consists of two applications: Transmitter application and Receiver application. Each application has real-time and off-line features. The Transmitter application generates HDLC test frames using special algorithms, transmits them over Datacom ports or records them to an HDL file for subsequent use with other applications.
The Receiver application can receive frames in real-time over Datacom or can verify an off-line HDL file for correct frame order and data integrity.