JBoss.orgCommunity Documentation

Mobicents ASN Library User Guide

by Amit Bhayani, Bartosz Baranowski, and Oleg Kulikov

Copyright © 2010 Red Hat, Inc.

Abstract

This User Guide introduces ASN Library.

Preface
1. Document Conventions
1.1. Typographic Conventions
1.2. Pull-quote Conventions
1.3. Notes and Warnings
2. Provide feedback to the authors!
1. Introduction to Mobicents ASN Library
2. Setup
2.1. Pre-Install Requirements and Prerequisites
2.1.1. Hardware Requirements
2.1.2. Software Prerequisites
2.2. Mobicents ASN Library Source Code
2.2.1. Release Source Code Building
2.2.2. Development Trunk Source Building
3. Design Overview
4. Protocol
4.1. Supported encoding rules
4.2. API
4.3. Examples
A. Revision History
Index

This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information.

In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts set. The Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not, alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes the Liberation Fonts set by default.

Four typographic conventions are used to call attention to specific words and phrases. These conventions, and the circumstances they apply to, are as follows.

Mono-spaced Bold

Used to highlight system input, including shell commands, file names and paths. Also used to highlight key caps and key-combinations. For example:

To see the contents of the file my_next_bestselling_novel in your current working directory, enter the cat my_next_bestselling_novel command at the shell prompt and press Enter to execute the command.

The above includes a file name, a shell command and a key cap, all presented in Mono-spaced Bold and all distinguishable thanks to context.

Key-combinations can be distinguished from key caps by the hyphen connecting each part of a key-combination. For example:

Press Enter to execute the command.

Press Ctrl+Alt+F1 to switch to the first virtual terminal. Press Ctrl+Alt+F7 to return to your X-Windows session.

The first sentence highlights the particular key cap to press. The second highlights two sets of three key caps, each set pressed simultaneously.

If source code is discussed, class names, methods, functions, variable names and returned values mentioned within a paragraph will be presented as above, in Mono-spaced Bold. For example:

File-related classes include filesystem for file systems, file for files, and dir for directories. Each class has its own associated set of permissions.

Proportional Bold

This denotes words or phrases encountered on a system, including application names; dialogue box text; labelled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:

Choose System > Preferences > Mouse from the main menu bar to launch Mouse Preferences. In the Buttons tab, click the Left-handed mouse check box and click Close to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand).

To insert a special character into a gedit file, choose Applications > Accessories > Character Map from the main menu bar. Next, choose Search > Find from the Character Map menu bar, type the name of the character in the Search field and click Next. The character you sought will be highlighted in the Character Table. Double-click this highlighted character to place it in the Text to copy field and then click the Copy button. Now switch back to your document and choose Edit > Paste from the gedit menu bar.

The above text includes application names; system-wide menu names and items; application-specific menu names; and buttons and text found within a GUI interface, all presented in Proportional Bold and all distinguishable by context.

Note the > shorthand used to indicate traversal through a menu and its sub-menus. This is to avoid the difficult-to-follow 'Select Mouse from the Preferences sub-menu in the System menu of the main menu bar' approach.

Mono-spaced Bold Italic or Proportional Bold Italic

Whether Mono-spaced Bold or Proportional Bold, the addition of Italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. For example:

To connect to a remote machine using ssh, type ssh username@domain.name at a shell prompt. If the remote machine is example.com and your username on that machine is john, type ssh john@example.com.

The mount -o remount file-system command remounts the named file system. For example, to remount the /home file system, the command is mount -o remount /home.

To see the version of a currently installed package, use the rpm -q package command. It will return a result as follows: package-version-release.

Note the words in bold italics above username, domain.name, file-system, package, version and release. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system.

Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. For example:

When the Apache HTTP Server accepts requests, it dispatches child processes or threads to handle them. This group of child processes or threads is known as a server-pool. Under Apache HTTP Server 2.0, the responsibility for creating and maintaining these server-pools has been abstracted to a group of modules called Multi-Processing Modules (MPMs). Unlike other modules, only one module from the MPM group can be loaded by the Apache HTTP Server.

Two, commonly multi-line, data types are set off visually from the surrounding text.

Output sent to a terminal is set in Mono-spaced Roman and presented thus: 

books        Desktop   documentation  drafts  mss    photos   stuff  svn
books_tests  Desktop1  downloads      images  notes  scripts  svgs

Source-code listings are also set in Mono-spaced Roman but are presented and highlighted as follows: 

package org.jboss.book.jca.ex1;

import javax.naming.InitialContext;

public class ExClient
{
   public static void main(String args[]) 
       throws Exception
   {
      InitialContext iniCtx = new InitialContext();
      Object         ref    = iniCtx.lookup("EchoBean");
      EchoHome       home   = (EchoHome) ref;
      Echo           echo   = home.create();

      System.out.println("Created Echo");

      System.out.println("Echo.echo('Hello') = " + echo.echo("Hello"));
   }
   
}

Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.

Note

A note is a tip or shortcut or alternative approach to the task at hand. Ignoring a note should have no negative consequences, but you might miss out on a trick that makes your life easier.

Important

Important boxes detail things that are easily missed: configuration changes that only apply to the current session, or services that need restarting before an update will apply. Ignoring Important boxes won't cause data loss but may cause irritation and frustration.

Warning

A Warning should not be ignored. Ignoring warnings will most likely cause data loss.

If you find a typographical error in this manual, or if you have thought of a way to make this manual better, we would love to hear from you! Please submit a report in the the Issue Tracker, against the product Mobicents ASN Library , or contact the authors.

When submitting a bug report, be sure to mention the manual's identifier: ASNLibrary_User_Guide

If you have a suggestion for improving the documentation, try to be as specific as possible when describing it. If you have found an error, please include the section number and some of the surrounding text so we can find it easily.

Abstract Syntax Notation One (ASN.1) is standard for describing data structures in telecommunication and computer networking world. ASN.1 provides a set of formal rules for describing the structure of objects. Specification describe abstract objects, that are independent of machine-specific encoding techniques.

ASN defined data can be encoded using on of encoding rules:

ASN.1 together with specific ASN.1 encoding rules facilitates the exchange of structured data especially between application programs over networks by describing data structures in a way that is independent of machine architecture and implementation language.

ASN encoded data looks logicaly as follows:

ASN encoding logical overview

Encoded data structure contains three elements:

2.1. Pre-Install Requirements and Prerequisites
2.1.1. Hardware Requirements
2.1.2. Software Prerequisites
2.2. Mobicents ASN Library Source Code
2.2.1. Release Source Code Building
2.2.2. Development Trunk Source Building

Ensure that the following requirements have been met before continuing with the install.

The Library doesn't change the Mobicents Hardware Requirements.

There are no specific software requirements.

  1. Downloading the source code

    Important

    Subversion is used to manage its source code. Instructions for using Subversion, including install, can be found at http://svnbook.red-bean.com

    Use SVN to checkout a specific release source, the base URL is http://mobicents.googlecode.com/svn/tags/protocols/asn, then add the specific release version, lets consider 1.0.0.BETA2.

    [usr]$ svn co http://mobicents.googlecode.com/svn/tags/protocols/asn/1.0.0.BETA2 asn-1.0.0.BETA2

  2. Building the source code

    Important

    Maven 2.0.9 (or higher) is used to build the release. Instructions for using Maven2, including install, can be found at http://maven.apache.org

    Use Maven to build the binaries.

    				    [usr]$ cd asn-1.0.0.BETA2
				    [usr]$ mvn install

    Once the process finishes you should have the binary jar files in the target directory of module.

Similar process as for Section 2.2.1, “Release Source Code Building”, the only change is the SVN source code URL, which is http://mobicents.googlecode.com/svn/trunk/protocols/asn.

Important

Be aware, Mobicents ASN Library is subject to changes as it is under active development!

Mobicents ASN Library has been designed as simple library which enables user to encode and decode streams according to ASN rules. It provides user with tools to process primitives and build more complex object according to definition in ASN.

Note

Mobicents ASN Library does not provide ASN compiler . It sole purpose is to avoid costly processing and allow user to implement desired functionality in optimal way.

4.1. Supported encoding rules
4.2. API
4.3. Examples

Mobicents ASN Library supports following encoding rules:

Mobicents ASN Library is stream oriented. User accesses ASN primitives by means of stream objects capable of proper decoding and encoding.

Following classes deserve explanation:

Simple decode integer primitive example: 



        

// integer -128

byte[] data = new byte[] { 0x2, 0x1, (byte) 0x80 }; //encoded form

ByteArrayInputStream baIs = new ByteArrayInputStream(data);

AsnInputStream asnIs = new AsnInputStream(baIs);

int tag = asnIs.readTag();

if(Tag.INTEGER==tag)

{

    long value = asnIs.readInteger();

    //do somethin

}


            

Simple encode Real primitive example: 



        

AsnOutputStream output = new AsnOutputStream();

output.writeReal(-3145.156d, BERStatics.REAL_NR1);  

        

Complex example how to decode some constructed data structure: 




// mandatory

    private Long invokeId;


    // optional

    private Long linkedId;


    // mandatory

    private OperationCode operationCode;


    // optional

    private Parameter parameter;

        

public void doDecoding( AsnInputStream ais )    

{

        

    int len = ais.readLength();

    if (len == 0x80) {

        throw new ParseException("Unspiecified length is not supported.");

    }

    

    byte[] data = new byte[len];

    if (len != ais.read(data)) {

        throw new ParseException("Not enough data read.");

    }

    

    AsnInputStream localAis = new AsnInputStream(new ByteArrayInputStream(data));

    

    int tag = localAis.readTag();

    if (tag != _TAG_IID) {

        throw new ParseException("Expected InvokeID tag, found: " + tag);

    }

    

    this.invokeId = localAis.readInteger();

    

    if (localAis.available() <= 0) {

        return;

    }

    

    tag = localAis.readTag();

    

    if (tag == Tag.SEQUENCE) {

        // sequence of OperationCode

    

        len = localAis.readLength();

        if (len == 0x80) {

            throw new ParseException("Unspiecified length is not supported.");

        }

    

        data = new byte[len];

        int tlen = localAis.read(data);

        if (len != tlen) {

            throw new ParseException("Not enough data read. Expected: " + len + ", actaul: " + tlen);

        }

        AsnInputStream sequenceStream = new AsnInputStream(new ByteArrayInputStream(data));

    

        tag = sequenceStream.readTag();

        if (tag == OperationCode._TAG_GLOBAL || tag == OperationCode._TAG_LOCAL) {

            this.operationCode = TcapFactory.createOperationCode(tag, sequenceStream);

        } else {

            throw new ParseException("Expected Global|Local operation code.");

        }

    

        if (sequenceStream.available() > 0) {

            tag = sequenceStream.readTag();

            this.parameter = TcapFactory.createParameter(tag, sequenceStream);

                

        } else {

            throw new ParseException("Not enought data to decode Parameter part of result!");

        }

    } else {

        throw new ParseException("Expected SEQUENCE tag for OperationCode and Parameter part, found: " + tag);

    }

}

        

Revision History
Revision 1.0Wed June 2 2010Bartosz Baranowski
Creation of the Mobicents ASN Library User Guide.

F

feedback, Provide feedback to the authors!