Overview

The HDLC is a protocol operating at the data link layer. The HDLC protocol embeds information in a data frame allowing data flow control and error correction. Each flag consists of eight bits - (01111110).

At the end of the frame, a Frame Check Sequence (FCS) is used to verify the data integrity. The FCS also known as cyclic redundancy check (CRC) is calculated using polynomial xˆ16 + xˆ12 + xˆ5 + 1 (FCS 16 bits) or xˆ0+xˆ1+xˆ2+xˆ4+xˆ5+xˆ7+xˆ 8+xˆ10+xˆ11ˆxˆ12+xˆ16+xˆ22+xˆ23+xˆ26+xˆ32 (FCS 32 bits). Idle periods in the data channel contain only flags.

GL's HDLC protocol analyzer provides the capability to capture, and analyze HDLC data on a full duplex T1 or E1 line. The data channel may utilize all or a fractional part of the T1 or E1 line. Also there may be multiple data channels within the T1or E1 line. After setting the HDLC data channel parameters and starting the decoding process, the main screen displays the received HDLC frames in hex format. Flags are stripped, all other data is presented, including CRC bytes.

GL Communications supports the following types of HDLC analyzers:

• Real-time HDLC Analyzer (Pre-requisites: GL's field proven E1 or T1 internal cards or USB Laptop E1 or T1 external units, required licenses and Windows Operating System)
• Remote/Offline HDLC Analyzer (Pre-requisites: Hardware Dongle and Windows Operating System)

In addition the following HDLC applications are supported that further help in transmitting and capturing pre-defined HDLC frames:

• HDLC Playback
• HDLC Impairment Utility
• HDLC Tx RxTest Application
• Automated HDLC Testing using Client-Server

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HDLC Analyzer Main Features

• Displays Summary, Detail, Hex dump, Statistics, and Call Detail Views; the contents of this view can also be copied to clipboard.
• Summary View displays timeslot, sub channel, frame#, device#, LAPD, LAPF specific information and IP information like source/destination IP address, TCP source port, TCP destination port etc.
• Supports decoding of LAPF, LAPD, LAPD+IP, LAPX+IP, X.25, Cisco HDLC Protocols.
• Detail View displays decodes of user-selected frames from the Summary View.
• Statistics View displays statistics based on frame count, byte count, frames/sec, bytes/sec etc for the entire captured data
• Hex dump View displays the frame information in HEX and ASCII format; the contents of this view can also be copied to clipboard.
• Supports filtering and search features based on C/R, SAPI, TEI, CTL, P/F, N(S), N(R) and FUNC
• Any protocol field can be added to the summary view, filtering, and search features providing users more flexibility to monitor required protocol fields.
• Capability to export Summary View details information to a comma delimited file for subsequent import into a database or spreadsheet.
• Capability to export detailed decode information to an ASCII file.
• Status bar displaying information regarding running percent utilization, Number of frames captured, CRC errors and Frame errors etc.
• Option to create multiple aggregate column groups and prioritize the groups as per the requirement to display the summary results efficiently
• Allows the user to create search/filter criteria automatically from the current screen selection
• Remote monitoring capability using GL's Network Surveillance System.

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Additional features supported by Real-time/Remote HDLC Analyzer:

• Streams can be captured on the selected time slots (contiguous or non-contiguous), sub-channels or full bandwidth. Frames may also be contained in either one, n x 64 kbps, or n x 56 kbps data channels.
• Other variations accommodated in the software are inverted or non-inverted data, byte reversal or non-reversal.
• Real-time capture filter can be set for filtering frames based on frame length.
• Multiple streams of HDLC traffic on various T1/E1 channels can be simultaneously decoded with different GUI instances.
• Supports decoding of frames with FCS of 16 bits and 32 bits, or none.
• Captured frames can later be used for traffic simulation using HDLC Transmit/Receive/Playback application.
• Multiple remote clients may access a single T1/E1 server, the T1/E1 server is fully functional while being accessed as a server. Thus, a user may perform T1/E1 operations locally on the server while a client is accessing the same server, in real time (For Remote Analyzers only).

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Additional features supported by Offline HDLC Analyzer:

• Trace files for analysis can be loaded through simple command-line arguments.
• Multiple trace files can be loaded simultaneously with different GUI instances for offline analysis.

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Supported Protocols

Following is a description of the protocols supported by GL's HDLC analyzer:

The supported protocol standards in HDLC analyzer are LAPF, LAPD, LAPD+IP, LAPX+IP, X.25, Cisco HDLC Protocols.

Supported Protocols	Specification Used
LAPD	CCITT Q.920/921
LAPF	ITU-T Q.922
IP	RFC 791
TCP	RFC 793
UDP	RFC 768
ICMP	RFC 792
STUN	RFC 3489
DNS	RFC 1035
DHCP	RFC 1533, 2131
HTTP	RFC 2616
FTP	RFC 959
SNMP	RFC 1157,1155,1902,3416,2863,2578,3418,2011,2012 etc
LAPB, X.25	ITU-T Recommendation X.25
Cisco HDLC	-
ARP	RFC 826

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Summary, Detail and Hex dump Views

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Real-time/Remote and Offline Analysis

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Filtering and Search

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Aggregate Column Group

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Statistics View

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Enhanced Trace Saving Options

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Save/Load All Configuration Settings

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Automated HDLC Testing using Client-Server

GL's Windows Client/Server software allows the user of T1/E1 analysis cards, the capability of remote operation, automation, and multi-site connectivity. Server software can run multiple tasks simultaneously at the request of the Client software. GL provides client -server based HDLC capture, playback, emulation & analysis modules.

WCS module XX640, XX641-File based HDLC Record/Playback & Remote Capture/Playback

The File based HDLC Record/Playback (Hdlcfunc) module is an optional application that allows HDLC Traffic Capture/Playback. It also allows transmission/reception of *.HDL frames files located on the server and on client.

Features

• Displays the command syntax.
• Receiving HDLC frames in HDL files located on the server.
• Transmitting HDLC frames from an HDL file located on the server.
• Receiving HDLC frames in HDL files located on the client.
• Transmitting HDLC frames from an HDL file located on the client.

For more information on this application visit HDLC Record/playback and Remote Record/Playback webpage.

WCS module XX634 - Multi-Channel HDLC Emulation and Analysis; File based High Throughput HDLC Record/Playback

The HDLCTerr module performs multi-channel HDLC emulation and analysis. It permits frame error testing and transmission of memory generated sequences of fixed or variable length HDLC frames, GL *.HDL Trace file frames, and various bandwidth streams.

The HDLCHpio module performs file-based HDLC record and playback actions. It permits receive / transmit of HDLC streams of various bandwidth (hyper channel, timeslot, and multiple sub-channel streams per timeslot).

For more information on these applications visit HDLC Frames Encode/Decode, and Error Testing webpage.

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Bridge and Monitor Connections

• Monitor from a DSX-Patch Panel
• Bridge Mode Connections for Monitoring T1/E1 Signals for RJ-45
• Bridge Mode Connections Alternative Method
• RJ-45 Connections

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Resources:

Please Note: The XX in the Item No. refers to the hardware platform, listed at the bottom of the Buyer's Guide, which the software will be running on. Therefore, XX can either be ETA or EEA (Octal/Quad Boards), PTA or PEA (tProbe Units), XUT or XUE (Dual PCIe Express) depending upon the hardware.

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