Internet Technology
NETW902
Final Exam
11th Jan. 2011
Please read carefully before proceeding:
1. This is an Open Book exam
2. The Exam duration is 2 hours
3. The exam booklet contains Pages including the cover page.
Viel Erfolg;
Problem 1
Question
Max. Pt.
Grade
Q1
Part I
Q2 Q3 Q4
Q5
Q1
12
30
20
6
20
6
Part II
Q2 Q3
19
27
Problem 2
Total
Q4
Q1
Q2
Q3
Q4
Q5
8
20
18
34
25
28
273
Problem 1 Internet Routing
Note:
Parts 1 and 2 can be solved independently of each other.
Part 1
Routing Algorithms
In Figure 1, the topology is sketched of an Internet Service Provider (ISP) network.
In the following tasks, various routing algorithms will be studied.
Question 1
Adjacency Matrix
a) Give the cardinality |V| and the size |E| of the graph G in Figure 1.
b) Construct the adjacency matrix A = (aij) of the graph G.
c) Interprete the connectivity of the nodes and their reflection within A.
Question 2
Distance Vector Routing Algorithm
a) Construct the routing table for the Distance Vector Algorithm hosted
in
a1) node 1
a2) node 8
b) Consider the case that link number 15 is interrupted due to an outage
of the transmission facilities.
Construct the Routing Table for node 8.
c) Describe shortly how the Routing Tables are kept up to date due to
events like equipment outages (links, nodes).
d) In the basic Distance Vector Routing Algorithm, nodes have only a
partial knowledge of the network state. Describe shortly how the
source-to-destination route is found.
e) How could the Distance Vector Routing Algorithm be upgraded to
follow estimates for the source-to-destination packet transfer delay?
Question 3
Link State Routing Algorithm
a) Construct the routing table for the Link State Algorithm.
A1) Which information contains the Link State Algorithm?
A2) Construct the Routing Table.
b) Describe how the source-to-destination route is found.
Question 4
Policy-Driven Routing Algorithms
Describe possibilities by which the source-to-destination path is found by policies rather
than routing tables.
Question 5
Autonomous Systems
Consider now the case where the network given by the graph of Figure 1 is subdivided
into 3 Autonomous Systems (AS) containing the following nodes:
AS 1: nodes 2, 3, 4
AS 2: nodes 1, 5
AS 3: nodes 6, 7, 8
a) Subdivide the graph of Figure 1 such that the 3 Ass are completely
separated where the links within each of the Ass are maintained from
the graph G.
b) Interconnect the Ass such that no AS remains isolated and that there
exist at least two different paths to interconnect any two of the three
Ass. Define Edge Routers for each AS accordingly.
c) Which routing protocol is adequate for the routing between Ass? Give
reasons for the idea of this routing protocol.
d) Which routing protocols can be applied?
D1) within an AS?
D2) between Ass?
e) Which information is exchanged between Ass and how is this
accomplished?
Part 2
Interworking between IPv6- and IPv4-Networks
As the IPv4 address space will soon be exhausted a strategy has to be developed for the
interworking between IPv6 islands across the IPv4-network.
In the following the case outlined in Figure 2 will be studied:
N3
IPv4
N1
IPv6
ER
1
H1
N2
IPv6
ER
2
Figure 2: Interworking between IPv4 and IPv6
Hosts H1 and H2 are connected to IPv6-networks N1 and N2 which are interconnected
by the IPv4-network N3 through Edge Routers ER1 and ER2, respectively. The Edge
Routers perform functions of a Gateway between the different network types. ER1 and
ER2 host the complete protocol stacks for
IPv4 and IPv6. H1 and H2 should be able to communicate between each other
exclusively through IPv6-packets and should not even be aware of trans-passing the
IPv4-network N3.
Question 1
Protocol Architectures
Sketch the principal layered protocol architectures of N1(N2) and N3 by
a) their protocol stacks
b) their packet formats.
Three principal methods are considered for the exchange of IPv6-packets between H1
and H2 across N3:
- Tunnelling
- Packet Header Translation
- Dual Protocol Stacks.
H2
Question 2
Tunnelling
a) Describe the method of Tunnelling by a sketch of the packet structure
used within N3 for the considered communication between H1 and H2.
b) Are there any changes required in the Routing Tables of the Edge Routers ? Give
reasons for your answer.
c) Are there any effects on the transport layer protocols UDP and TCP running within
H1 and H2 ? Give reasons for your answer shortly.
Question 3
Packet Header Translation
By 'Packet Header Translation' IPv6-packets will be translated packet-by packet into
IPv4-packets to be routed and forwarded through N3.
a) Identify the principal problems arising with this method.
Hint:
Consider the main elements of the packet headers for IPv4 and IPv6.
Discuss which functions are candidates for a translation and, as a result of it, whether
there exists a full equivalence at all.
b) Discuss shortly the problem of routing and forwarding of packets.
Question 4
Dual Protocol Stacks
By 'Dual Protocol Stacks' all routers in the networks would have to be upgraded such that
they can handle both types of packets and protocols.
With the increasing degree of maturity of the change from IPv4 to IPv6 the
IPv4 stacks could be taken out of operation.
A simple looking, but more expensive, solution would be a complete duplication of all
routers in hardware and software, i.e. a one-to-one overlay of IPv4 and IPv6 networks.
a) Discuss this solution with respect to the assignment of IP addresses.
b) At which layers can both networks be integrated and at which layer do they have to
be separated ?
Problem 2
Flow, Congestion, Traffic and QoS Control
In this problem main control aspects will be studied which are used in the internet and
other services integrated networks.
Note: Questions 2,3,4 and 5 can largely be solved independently of each other.
Question 1
Purposes of Control Actions
a) Define shortly the purpose of
a1) Flow Control (FC)
a2) Congestion Control (CC)
a3) Traffic Control (TC)
a4) Quality of Service Control (QoSC)
b) Identify
b1) the instances (such as source host, destination host, network)
being involved in the respective control actions
b2) the criteria upon which the control action is initiated.
Question 2
Mechanisms for Flow Control
a) Name principally different mechanisms used for FC actions.
b) Which FC mechanisms are used in TCP ?
Identify the parameters used in TCP for FC and illustrate the control action by a
generic temporal signalling diagram.
c) To utilize network resources more effectively ISP's use Load-Balancing mechanisms
by which the packet load is more evenly distributed across various links. Discuss the
effect of Load Balancing on Flow Control.
Question 3 Mechanisms for Congestion Control
a) Name principally different mechanisms used for CC actions and classify them with
respect to the identified instances (c.f. Question 1, b1).
b) Which CC mechanisms is used for TCP ?
Identify the parameters used in TCP for CC and illustrate the control action by a
generic state transition diagram and a temporal signalling diagram.
c) Which other CC mechanisms are used where the network is involved?
In which sense does 'Load Balancing' belong to CC?
Question 4 Mechanisms for Traffic Control
a) Name principally different mechanisms for TC actions.
b) Which TC mechanisms are used in:
b1) ATM networks
b2) the internet ?
Identify the parameters which are applied in these TC methods.
c) Example:
A traffic stream of cells (ATM network) or of packets (internet) shall be controlled
with respect to the conformance with parameters of a "Traffic Contract" (i.e.,
quantitive metrics for the peak cell or peak packet rate, and a limited tolerance with
respect to some "burstiness").
Which algorithms are used:
c1) for ATM?
c2) for the Internet?
Give the name and the parameters of both algorithms.
Question 5 Mechanisms for Quality of Service Control
a) Which parameters characterize Quality of Service on the network layer in
a1) ATM networks?
a2) The Internet?
b) Name principally different mechanisms/protocols to enhance QoS and which are
applied in
a1) ATM networks
a2) The Internet.
Describe these mechanisms shortly.