Computing 205/406 & IT8

Tutorial #14

1. In the lecture, the concept of abstract versus concrete representation of data types was introduced. Explain briefly the meaning of each of these terms.

2. Why are the Basic Encoding Rules (BER) needed for ASN.1?

3. Express the following ASN.1 specification in terms of an imperative language such as C or Pascal with which you are familiar:

   name ::= OCTETSTRING -- or IA5String
   married ::= BOOLEAN
   yrsWithCompany ::= INTEGER
   

4. Describe how each of the specifications in Q.3 would be encoded using BER. Note that we don't have actual values for the data items, so you'll have to make some up.

5. The following is a record declaration in the Pascal language. Express this in terms of ASN.1

   personnelRecord = record
   	name : array[1..100] of char;
   	yrswithCompany : integer;
   	married : boolean
   end ;
   

6. Which of the following ASN.1 syntactic elements would you expect to be keywords, types and variables?

   AP-Title
   ipInReceives
   ENUMERATED
   ObjectDescriptor
   OCTET STRING
   sysDescr
   

7. You receive the following string of BER-encoded octets, values given in hexadecimal. What does it mean?

   30 08 02 01 03 04 03 48 69 21