Computer  Science 826
                        Quiz 8  -  Name ________________________

We identified two possible strategies that could be used by
an EGP router when it received an "I can reach network N" message
from neighboring AS "A"

   Strategy 1: If this is the first such message pertaining to network
               "N" add it to the routing table and propogate it. Else
               ignore and discard it.

   Strategy 2: Always use and propogate the most recently received
               "I can reach N" message -- replacing any existing
               information if it exists.

1. Which strategy is most likely to lead to routing loops:

   a. 1                          b.  2

   c. both equally likely        d.  neither

2. Which strategy provides a better capability to respond to
   changes in topology.

   a. 1                          b.  2

   c. both equally likely        d.  neither

3. The receipt of multiple "I can reach N" messages is not a
   problem in (circle all that apply)

   a. Linear networks            b. tree networks

   c. general graph networks

4. Although tree networks have certain nice properties they
   have one very UNDESIRABLE property when compared to more
   richly connected graphs ... what is this problem??






5. The transport used by OSPF is:

   a. IP packets with a private        b. ICMP
      protocol number

   c. UPD                              d. TCP

6. A routing update generated by an OSPF router propogates (we are talking
   about the actual packets themselves -- not indirectly derived information)

   a. Across the entire internet       b. Across an entire AS

   c. Across a single network          d. Only to directly attacted routers

7. In the cost matrix used to create OSPF routing tables the
   row and column indices are:

   a. IP network addresses             b. AS numbers

   c. Router ids                       d. Link state ID's

The next three question relate to Paxson's Paper:

8. The basic mechanism used by Paxson to detect routing pathologies
   was

   a. ping                             b. traceroute

   c. TCP connect requests             d. e-mail messages

9. The basic thrust of Paxson's paper was to characterize

   a. the cause of routing loops       b. the frequency and duration
      in the internet                     of routing loops

   c. all causes of dropped packets    d. (a) and (b) apply equally

10. Near the end of the paper Paxson presents a short discussion
    on routing asymmetry. He lays part of the blame for asymmetries
    on competing ISP's using a "Hot Potato" strategy. Exactly
    how does this lead to routing assymetry.













11. An OSPF advertisement whose  link-state ID is that of a network
   carries link ID's of

   a. directly attached networks        b. directly attached OSPF routers

   c. directly or indirectly attached
      networks or routers.

12. An OSPF advertisement whose  link-state ID is that of a router
    carries link ID's of

    a. directly attached networks        b. directly attached OSPF routers

    c. directly or indirectly attached   d. directly attached OSPF routers
       networks or routers.                 or networks

13. The transport used by BGP is:

   a. IP packets with a private        b. ICMP
      protocol number

   c. UPD                              d. TCP