Computer Networks

Tutorial #17

1. How would you request a router to return the actual values of the objects ipForwarding, icmpInEchoes and tcpMaxConn? Give solutions using each of the get and get-next commands. Use a command syntax of your choice, although the CMU SNMPlib syntax given in the lecture notes would be the most appropriate.

2. The following is a diagrammatic view of portion of a table (ifTable) in the interfaces portion of the standard MIB, edited to fit the page. The table consists of a sequence of ifEntry elements. Values shown are from the router r-bgowan at Bendigo.

   

   1. Describe interface 3 on this router.
   2. What would be the structure of an SNMP get-request to discover the speed, in bps, of interface 1.
   3. What value would be returned by get-next(...ifSpeed.2)?

3. Why do SNMP proponents use the expression "powerful get-next"? In other words, what problem does the get-next operation solve very elegantly?

4. (Philosophical question) What is the purpose of the SNMP portion of the MIB?

Practical exercises:

• Use tkined to discover routes to selected Internet hosts and display the network map. Investigate some of the (very powerful and fully industrial strength) functions available in tkined.

• Use the CMU SNMP utilities in the directory /usr/local/snmp on our Unix systems. Try fetching the MIB variable system.sysDescr.0 from various departmental systems, and thus learn which are running SNMP.

• One of the current Big New Things is the integration of SNMP, and network management in general, with the WWW. You can see an excellent example of this at the URL http://ironbark.bendigo.latrobe.edu.au/information/mrtg/ Have a look. Of particular interest is the ATM (microwave) link between Bendigo and Bundoora!