Networks

Question 1

Operating Systems Role

Answer 1

Manage the computer’s resources
Memory management
Scheduling
Access Controls

Question 2

Characteristics of Network Topologies

Answer 2

# of connections
# of “hops”
Addition of new nodes
Fairness
Collisions and points of failure

Question 3

Protocol defined parameters

Answer 3

Type of error checking
Data compression method
Mechanisms to signal reception of a transmission

Question 4

DNS Port

Answer 4

53

Question 5

Static Routing

Answer 5

Static: entries entered once and not updated

Question 6

Routing Information Protocol (RIP):

Answer 6

entire tables shared on a periodic basis. Not very efficient or secure.

Question 7

Open Shortest Path First (OSPF):

Answer 7

Table maintained to determine what the shortest path is to specific destinations. Tremendous overhead.

Question 8

Border Gateway Protocol (BGP):

Answer 8

Peer routers (neighbors) exchange routing information. Entire table initially loaded but subsequent changes limited to updates.

Question 9

ICMP performs the following controls:

Answer 9

• Flow Control
  
  • Detecting unreachable destinations
  • Redirecting routes
  • Checking remote hosts (e.g. ping)

Question 10

Types of DOS attacks

Answer 10

Flooding – sending more data than the target can process
Crashing – sending data, often malformed, designed to disable the system or service
Distributed – using multiple hosts in a coordinated attack effort against a target system.

Question 11

IPv4 vs. IPv6

Answer 11

scalability:IPv6 uses 128bit address space. Address length is 4 times longer than IPv4.
security:IPv6 basic specification includes security. It includes packet encryption (ESP:Encapsulated Security Payload) and source authentication (AH:Authentication Header). [confidentiality and authentication]
real-time:To support real-time traffic such as video conference, IPv6 has “Flow Label”. Using flow label, routers can know which end-to-end flow a packet belongs to, and then find out the packet which belongs to real-time traffic. [needed to allow for prioritization of traffic]
autoconfiguration:IPv6 basic specification includes address autoconfiguration. So, even a novice user can connect their machine to network.
specification optimization:IPv6 keeps good parts and discards old and useless parts of IPv4.

Question 12

Two major modes of IPSec

Answer 12

Tunnel: encrypts both the data and header portions of the packet.
Transport: encrypts the data portion of the packet.

Question 13

provides authenticity guarantee for packets, by attaching strong crypto checksum to packets. If you receive a packet with AH and the checksum operation was successful, you can be sure about two things :
The packet was originated by the expected peer. The packet was not generated by an impersonator.
The packet was not modified in transit.

Answer 13

IPSec Authentication Header (AH)

Question 14

provides confidentiality guarantee for packets, by encrypting packets with encryption algorithms. If you receive a packet with ESP and successfully decrypted it, you can be sure that the packet was not wiretapped in the middle.

Answer 14

Encapsulating Security Payload (ESP):

Question 15

ESP provides encryption service to the packets. However, encryption tends to negatively impact compression on the wire. IPcomp provides a way to compress packets before encryption by ESP (Of course, you can use IPcomp alone if you wish to).

Answer 15

IP payload compression (IPcomp):

Question 16

AH and ESP need shared secret keys between peers. For communication between distant locations, we need to provide ways to negotiate keys in secrecy. IKE will make this possible.

Answer 16

Internet Key Exchange (IKE):