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csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_csn_1_vs_asn_1.html

CSN1 vs ASN.1. CSN1 vs ASN.1. Although their acronyms are similar, CSN.1 is substantially different from ASN.1. ASN1 defines an abstract data structure: in other words, an ASN.1 specification tells you, for example, that we have a structure with some fields in it, or a union, an array and so on. In ASN.1 we describe our data structure as we do when we are declaring C structs. My data : = 1 x: bit(8) 0 y: bit(4) 0;. In other words, it generates code that will say to you: hey, I found the 1 followed by the...

csn1.info

CSN.1 Explained

http://www.csn1.info/index.html

CSN1 vs ASN.1. Welcome to the csn1.info. Website. This site contains a description of the CSN.1 (Concrete Syntax Notation 1) language widely used by ETSI and 3GPP for the encoding of 2G/3G messages. The information here reported are taken from official documents and integrated by the long experience made by Dafocus. In the encoding/decoding field. Which is sponsoring this site, is the maker of Encodix. Basic concepts of CSN.1. The Bx rules of CSN.1. The Ax rules of CSN.1. Other even more advanced rules.

csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_other_rules.html

CSN1 vs ASN.1. The send construction can be used to differentiate a string to be used when decoding with the one to be used for encoding. The send construction has the following syntax:. The send construction is used for example to force a stricter encoding and allow a more relaxed decoding. In this example, the data is 5 bit long (. The remaining three bits are always encoded as 000; however, when decoding, the decoder reads, accepts and discard any three bits it will find:. Bit bit = 00;. Is the same of.

csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_advanced_rules.html

CSN1 vs ASN.1. The label allow assigning a name to a defined substring inside a CSN.1 definition. In this way, it is possible to mark where the message information is and to distinguish it from the other support bits. The format for a label is:. In the next example, our goal is to define a string that transports a 1-bit value or a 3-bit value; in order to distinguish the two cases, the protocol uses a control bit:. Followed by the 1-bit value, or. Followed by the 3-bits value. Label : foo bar. Foo bar : ...

csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_pitfalls.html

CSN1 vs ASN.1. As explained in the introduction. The CSN.1 language was designed to make life easier by giving a formal and unambiguous definition of the message structure. However, due to the difficoulty of writing the encoding with such a language, 3GPP definitions are often wrong. In this chapter shows some CSN.1 pitfalls that can be found on 3GPP standards. Often the errors are due to wrong precedencies. Wrong use of sendconstruction. In the example below, the bold part shows the error location.

csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_introduction.html

CSN1 vs ASN.1. The CSN.1 formal language has been introduced by 3GPP at the end of the 90's to describe mostly the encoded format of GSM L3 messages. Before that, those encoding were expressed only by mean of various unformal tables and text parts, describing the meaning of each bit. The goals of CSN.1 were to:. Have a unified language for all the description;. Describe the encoding formally;. Encourage the creation of automatic encoding/decoding generators;. Message escape : 1 bit (*) = no string }!

csn1.info

CSN.1 Explained

http://www.csn1.info/csn1_core_rules.html

CSN1 vs ASN.1. The CSN.1 strings are built up using operators like math formulas. The various operators have precedencies. In order to control the exact sequence of the operators, CSN.1 uses the curly braces (. The same way mathematics uses the parenthesis. Foo bar : = 10 {. The most basic symbols available to CSN.1 are those related to the values. A CSN1 string can match. There are only two values that can be matched: 0 or 1. Therefore:. These two statements match a 1-bit long string. 001 1 0 001. The u...