Computer Networks

Tutorial #15

1. What information can the network manager obtain from the ping command? Give at least 3 answers. What does ping actually do?

2. What does the traceroute command tell the network manager? Why is traceroute not recommended for use in regular network monitoring? (Hard research question:How does traceroute work?)

3. The ASN.1 APPLICATION-specific data types of SNMP mostly use the sub range feature of ASN.1, which we didn't actually mention in our introductory ASN.1 lecture. What is the significance of the sub range values for the SNMP ASN.1 APPLICATION types Counter and Gauge?

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

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

   What are the numeric OBJECT IDENTIFIERS of the objects ipForwarding, icmpInEchoes and tcpMaxConn.

5. (Extension Question) One interesting aspect of the ASN.1/BER is the way in which OBJECT IDENTIFIERS are encoded for transmission. In general, the integers which specify the OBJECT IDENTIFIER are simply encoded in BER as a SEQUENCE of single byte values. However, the first two integers (let's call them a and b) are encoded in a compact form, taking only a single byte, of the form 40a + b. So, for the Internet, the first two integers are 1.3, therefore they are encoded as the single byte value 43. Can you imagine a reason why this is done? What does it say about the values of these first two integers?

6. (Extension Question) Marshall T. Rose^[1] espouses the fundamental axiom of network management, which is: The impact of adding management to managed nodes must be minimal, reflecting a lowest common denominator. Discuss.