Network Management midterm study guide

Network Management Midterm Study Guide

Dordal

Here are the OpenFlow sections from An Introduction to Computer Networks that you should be familiar with:

2.7 Software-Defined Networking
- 2.7.1 OpenFlow Switches
- 2.7.2 Learning Switches in OpenFlow: This is important! The book was recently updated here, to include more detailed analysis of the OpenFlow pairs approach (l2_pairs.py) and the two-table approach (l2_nx.py).

Also the following, with the understanding that Python won't be on the exam:

18.8 The POX Controller
- 18.8.1 hub.py
- 18.8.2 l2_pairs.py
- 18.8.3 l2_nx.py

Here are the SNMP sections that may be covered, from the SNMP chapter:

21.1 Network Architecture: general stuff; won't be on the exam
21.2 SNMP Basics: basic background
21.3 SNMP Naming and OIDs: important, though only for the SNMP part of the OID tree
21.4 MIBs: Know what these are, and basically how to read them
21.5 SNMPv1 Data Types: Not important for the exam, but know what an octet string is
21.6 ASN.1 Syntax and SNMP: not very important
21.7 SNMP Tables: this is important! Table (col,row) format, table indexing, OIDs of table components
21.8 SNMP Operations: this is important too, in particular how Get() and GetNext() work (and GetBulk())
21.9 MIB Browsing: won't be on the exam as such
21.10 MIB-2: you should be familiar with the system, interfaces and maybe ip groups
21.11 SNMPv1 communities and security: not significant for the exam
21.12 SNMP and ASN.1 Encoding: not significant for the exam
21.13 SNMPv2: GetBulk(). Specific SNMPv2 MIBs might be mentioned, but if so they'll be explained to the level necessary.

Here's a summary of important SNMP-Table topics without reference to sections from the book:

how tables are represented as OID trees
how tables are indexed
how GET-NEXT can be used to traverse a tree
variants in use of SNMPv1 GET-NEXT:

retrieving an entire row
retrieving only the non-index column(s)

You will be given copies of the mib-2 system and interfaces group definitions from this slightly edited version of the RFC1213 MIB. (Actually, because this exam is online, I will most likely include a link to the full MIB as well).

The midterm covers up through SNMP version 2.

Answers are now here.

(For some of these examples, you may need to look at the answer to figure out what I'm talking about And remember that you will have some MIB file (probably part of RFC1213) to use as a syntax reference.)

For OpenFlow, see these exercises at intronetworks.cs.luc.edu/current/html/ethernet.html#exercises:

10.0
12.0
12.2
13.0
14.0

1. Suppose we want to create a new snmp table, called carTable. The prefix is vehicles::= 1.5.4.3.2. The carTable is to consist of sets of entries of form
   horsePower
   make (gm, chrysler, ford, nissan, toyota)
   modelNumber
   seating
The index is to be a field carNum.

Give an ASN.1 definition for carTable, carEntry, and the entry fields. Model it after ifTable.

(This is a general problem on how to define tables)

2. What is the problem with conventional switches and a loop topology, and how are OpenFlow/SDN switches able to accommodate this?

s1------s2
    |       |
    s4------s3

3. What is the simplest way, using SNMP, to
(a) retrieve a single row of a table (say row 3, where the columns are T.1 through T.7)
(b) retrieve a single column of a table (say column 5, with pseudo-header T.5, and 6 rows)

5. In the IP group, mib2.4, part of RFC1213-MIB, there are several tables:
   ipAddrTable
   ipRouteTable
   ipNetToMediaTable
The following apply to the last table.
(a). List the columns under ipNetToMediaEntry.
(b). Draw a table representing these entries. Create at least two rows. Make up plausible values.

7. Suppose you are on a subnet. One workstation on the subnet is also a router to the outside world. What SNMP tables might help you to determine which workstation is the router?

What if the workstation were a switch and not a router?

8. Account for the differences between TCP and UDP in the RFC1213-MIB (mib-2). That is, explain the differences and explain why they are there.

9. Consider a simplified version of the RFC1213-MIB Interfaces table (some columns described in M&S, p 349), with entries for ifIndex, ifDescr, and ifSpeed.
(a). Give the OIDs for the columns themselves.
(b). Suppose the table has the following data:

ifIndex	ifDescr	ifSpeed
1	eth0	10,000,000
2	eth1	100,000,000

Give the full OIDs for each of these six table entries.

You may express the OIDs as either 1.3.6.1.2.1._________ or as mib-2.________

10. Consider the ETHERLIKE-MIB for ethernet-like nodes, and
(a) identify how to find the number of collisions
(b) identify how to determine if any host is violating the 1500-byte maximum packet size
(c) identify how to determine the rate of collisions per good packet.

11. Be familiar with get-next traversal, and at least somewhat familiar with the get-bulk extension. In what order will values be retrieved from the following table?

                           |
                      +---------+
                      |         |
                      |    T    |
                      |         |
                      +---------+
                           |
                           |
                      +---------+
                      |         |
                      |    E    |
                      |         |
                      +---------+
                           |
                           |
         +-----------------+-----------------+
         |                 |                 |
    +---------+       +---------+       +---------+
    |         |       |         |       |         |
    | T.E.1.1 |       | T.E.2.1 |       | T.E.3.1 |
    |         |       |         |       |         |
    +---------+       +---------+       +---------+
         |                 |                 |
    +---------+       +---------+       +---------+
    |         |       |         |       |         |
    | T.E.1.2 |       | T.E.2.2 |       | T.E.3.2 |
    |         |       |         |       |         |
    +---------+       +---------+       +---------+
         |                 |                 |
    +---------+       +---------+       +---------+
    |         |       |         |       |         |
    | T.E.1.4 |       | T.E.2.4 |       | T.E.3.4 |
    |         |       |         |       |         |
    +---------+       +---------+       +---------+

12. Consider the network below, in which switches s1-s4 each have port numbers 1, 2 and sometimes 3 as shown

h1          h2          h3          h4
|         |         |           |
1         1         1           1
s1-2------2-s2-3------2-s3-3------2-s4

Give flow-table entries for S1-S4 (or just S1 and S2) that match any traffic between the hosts using the l2_pairs approach. For example, s1 will include the following rules:

src=h1,dst=h2: forward out port 2
src=h2,dst=h1: forward out port 1
src=h1,dst=h3: forward out port 2
src=h3,dst=h1: forward out port 1
src=h1,dst=h4: forward out port 2
src=h4,dst=h1: forward out port 1

(this is all for s1, because any traffic not involving h1 will not pass through s1.)

13. Do the same as in 12 above, except give the forwarding entries if the l2_nx approach (two tables, T0 and T1) are used. Assume T0 is used to match destination addresses and T1 is used to match source addresses. The default rules for each table are as follows:

T₀: match nothing: flood, send to T₁

T₁: match nothing: send to controller