INT21CN Computer Networks

Tutorial #22

1. What on earth does "disambiguate" mean?

2. In general terms, how is an ASN.1 object encoded for transmission in the BER? Give an example of a small-valued integer which has been encoded in this way. Then give an example of an OCTET STRING.

3. What is the significance of the sub-range values for the SNMP ASN.1 APPLICATION types Counter and Gauge? The answer may not be immediately obvious!

4. The following are some (highly edited) entries from the standard Unix MIB-II definition, from /etc/mib.txt.

   ipForwarding OBJECT-TYPE ::= { ip 1 }
   icmpInEchos OBJECT-TYPE ::= { icmp 8 }
   tcpMaxConn OBJECT-TYPE ::= { tcp 4 }
   

   What are the full numeric OBJECT IDENTIFIERS of the objects ipForwarding, icmpInEchoes and tcpMaxConn. Express each of them in the various "mixed" formats presented in the lecture.

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

   30 08 02 01 03 04 03 48 69 21