Possible questions for the examination
These
questions are given as example questions for the exam. Most exam questions will
be based on these examples. However, this is not an exhaustive list.
PSTN/ISDN
- What is routing, and what
are its possible goals?
- What are the main functions
of routing and their main characteristics?
- What are the advantages and
disadvantages of centralizing and distributing routing?
- Spell out and explain
briefly FHR, AAR, DAR, DNHR, LLR, RCAR,
and DCR.
- Describe briefly the
following concepts related to circuit-switched networks: fixed
hierarchical routing (FHR), adaptive routing, crankback.
- Describe the principle and
the algorithm of fixed hierarchical routing (FHR).
- Explain the principle of
number analysis in a telephone exchange.
- Explain the relationship
between routing and (subscriber) number portability. Describe the
architecture realizing number portability in Finland.
- What is meant by routing in
circuit-switched networks? What is meant by dimensioning the network?
- Compare the use of global
and local information in routing. Give an example of a PSTN routing
algorithm that uses only local information. Give also an example of a routing
system in the circuit switched network that uses global information.
- Show the taxonomy of the
routing systems in circuit switching.
- Compare the use of local
and global information in routing.
- Describe the operating
principle of alternative routing. Use an example.
- What is meant by an optimal
route? Explain the interest conflict between one user and all users
concerning optimality.
- Describe the principle of
fixed hierarchical routing and the algorithm for routing.
- Explain the principles of
originating office control and sequential office control using a routing
tree.
- The nodes A, B, C and D
form a completely looped network. Node E connects to A and C. Describe,
from the user’s point of view, optimal routing from B to D using the
augmented routing tree.
- For what is an influence
graph needed? Give an example of the use of the influence graph.
- Provide an example on cross
overflow and analyze the case using an influence graph.
- Explain the principle of
adaptive routing
- Explain the principle of
DAR routing. Explain also the use of trunk-line reservation parameters in
DAR.
- Explain the principle of
DAR. What variations of the algorithm exist?
- Describe the DAR routing
algorithm used by BT. Give also the algorithm of general sticky principle.
- Describe BT’s routing
algorithm based on DAR.
- Explain the routing
algorithm of the general sticky principle (yleinen
tartuntaperiaate).
- Describe the routing
principle of the long-distance network of Canada.
Internet
- What information of the IPv4
protocol headers does the Internet routing utilize?
- Explain the basic method
for the Internet to recover from routing loops. How does the network
recover from black holes?
- What are the current
principles of Internet addressing?
- Considering routing (addressing),
explain how the IP protocol is adapted to the underlying network.
- Explain how IP routing is
adapted to a situation where there are several routers in one LAN segment.
- Compare the headers of IPv4
and IPv6. Which are the main differences? How are extensions implemented
in IPv6?
- Stateless autoconfiguration in IPv6.
- How did CIDR change
Internet routing?
- Define the autonomic
system. Describe the structure of Internet on the level of autonomic
systems.
Distance-vector routing protocols
- Describe the reception
algorithm of distance vector protocol.
- Describe the functioning
principles behind RIP using a little example network. (There are no faults
in the network and all links weights are 1).
- Using an example, describe
how RIP recovers from losing a link. (The link weights are all equal).
- Routing loops – how
do they appear, what problems do they cause, how can they be prevented?
- Show the birth of a
transient routing loop in a RIP-network using an example.
- Show using an example that
the RIP-network recovers from a transient routing loop.
- When does the use of RIP
lead counting infinity?
- What countermeasures for
routing loops can be built into distance vector protocol?
- Show, that a routing loop
is possible even if the distance vector protocol uses poisonous vectors.
- When does it pay off for
the DV-protocol to send?
- Evaluate the applicability
of the distance vector protocol to Internet routing.
- Give the Bellman-Ford
algorithm.
- Enumerate the basic
characteristics of RIP.
Link-state routing protocols
- Compare distance-vector and
link-state routing protocols. What are the advantages of link-state
routing compared to distance-vector routing?
- Illustrate the principle of
Internet routing based on the link state approach.
- Illustrate the algorithm for
distributing the link states in link-state routing.
- How is the fractioned
network re-united in link-state routing?
- What actions can be taken
to ensure the integrity of the link-state databases in link-state routing?
- Illustrate the Dijkstra algorithm of shortest-path-first without
alternative paths.
- Illustrate Dijkstra’s shortest-path-first algorithm that
can also detect alternative paths.
- The pros and cons of
distributing packet traffic to alternative paths.
- What are the protocols used
with OSPF? Explain the concept of neighborhood in OSPF.
- Explain the OSPF flooding
protocol in broadcast networks and in point-to-point networks.
- Explain the concept of area
in OSPF.
- Illustrate the principle of
recovery from internal (to an area) failure in OSPF. How can virtual links
be used in the recovery?
- Explain the concepts of
stub-area and not-so-stubby-area in OSPF.
- Illustrate the algorithm
with which the OSPF chooses the designated router and the Back-up
designated router.
- Present the types of state
records and their usage in OSPF.
- Explain the actions
relating to the age of the state record in OSPF.
- Illustrate the use of OSPF’s network-LSA in reducing the size of the
link-state database.
- Present the suitable
network topology models of OSPF for ATM and Frame Relay networks.
- Describe the contents of
the link state database and the routing table of an OSPF router. How are
these constructed?
Multicast
- Multicast applications and
intended uses in the Internet. How does the communication based on
multicast differ from the typical communication model of the
point-to-point communication?
- Define the graph-related
concepts: graph, neighbor, simple graph, multigraph,
path and loop.
- Define the graph-related
concepts: connected graph, directed graph, tree, spanning tree and forest.
- Present the data structures
that are used to describe graphs.
- Give the algorithm that
creates the minimal spanning tree from a given graph.
- Why the minimal spanning
tree (MST) is not used in the practical solutions of multicast in the
Internet? How does the RPF multicast routing differ
from the MST based solution?
- RPF algorithm and its
characteristics.
- What are the two different
ways that the multicast can be limited to a changing group of receivers?
- Compare the advantages and
disadvantages of the center-based tree algorithm and the “flood and
prune” algorithm.
- Present IGMPv2 and v3.
- Present the principles of
DVMRP.
- What is a dependent
downstream router in DVMRP? What is a designated forwarder?
- How are
the neighborhood relations handled in DVMRP?
- The construction and
updating of source trees in DVMRP.
- The multicast algorithm of
DVMRP in a router.
- Explain the use of cached
information in DVMRP to minimize the multicast trees.
- The handling of Prune and
Graft messages in DVMRP.
- The principle of MOSPF
multicast routing.
- How does the MOSPF use Dijkstra’s algorithm?
- How can MOSPF be introduced
gradually in an OSPF domain?
- The effects of hierarchy to
multicast routing in MOSPF.
- How do dense and sparse
multicast groups differ? Which protocols are best suited for these groups
and why?
- Why does PIM-DM delay
before executing a prune on a broadcast network? What happens if two
routers forward the same multicast group to a broadcast network?
- What is the rendezvous
point (RP) in PIM-SM? How is a RP selected for a group is there are
several?
- Describe how packets are
sent to a multicast group in PIM-SM.
- Assume two neighboring
networks connected by two routers. One network uses DVMRP and the other
uses PIM-SM. How is a multicast transferred between them?
Mobile IP
- Describe the elements
involved in mobile IP (IPv4 assumed). How is a packet routed to and from a
mobile host?
- Explain the discovery and
registration procedures in mobile IP (IPv4 assumed).
- How can a mobile host
determine that it is visiting a different network than before?
- A mobile host wants to
participate in a multicast conference in its home network. How does it
join the conference? How are the multicast packets transferred to the
host?
- Why is source address
filtering used? How does it decrease the performance of mobile IP? How is
the problem solved in IPv6?
- What does triangle routing
mean? Why must the packets be tunneled in both directions sometimes? How
can the path to a mobile host be shortened in IPv6?
- The function of the Foreign
Agent in Mobile IPv4 and Mobile IPv6.
- Compare encapsulation in
Mobile IPv4 and Mobile IPv6.
Routing in Ad hoc networks
- What characteristics are
typical to mobile ad hoc networks? How do these properties affect routing?
- What is the difference
between proactive and reactive routing? Describe the main methods of
obtaining routes for both types. Give examples of some protocols of both
types.
- Describe the operation of
the DSR (Dynamic Source Routing) protocol.
- Describe the operation of
the AODV (Ad-hoc On-demand Distance Vector) routing protocol.
- The use of sequence numbers
in AODV (Ad-hoc On-demand Distance Vector).
- How does the Zone Routing
Protocol (ZRP) combine proactive and reactive routing? What function do
the peripheral nodes have?
- Present a classification of
routing protocols for ad hoc networks. What are the main features of each
class?
- How can geographical
information be utilized for routing in Ad hoc networks?