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Networks > Network Layer > Flashcards

Network Layer Flashcards

1
Q

What are the main network protocols?

A

IPv4
IPv6
ICMP - Internet Control message protocol (e.g. ping)
IPSEC - Adds authenication datagram to header.

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2
Q

What are the features of IPv6?

A

128-bit addresses.
Colon-hex format
Leading 0s can be replaced with “::”

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3
Q

How are subnets represented?

A

CIDR - Classless Inter Domain Routing

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4
Q

What are the 6 address scopes of IPv6?

A 
Loopback 
Link-Layer (used only on link layer)
Multicast 
Unqiue Local (used within a site)
Global Unicast
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5
Q

What replaces ARP and ICMP Routing Advertisement in IPv6?

A

ICMPv6

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6
Q

Whatare the 5 packet types of ICMPv6?

A 
Router Solicitation
Router Advertisment
Neighbour Solicitation (ARP equiv)
Neigbour Advertisment (ARP reply equiv)
Redirect (when 'better' first hop found)
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7
Q

What is router advertisement?

A

A router sending out its address and other data in reponse to a Router Solicitation or as part of its periodical functionality (every 600 seconds).

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8
Q

What does a Router Advertisement message contain? (3)

A

Network prefix
Router address
DNS information (optional)

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9
Q

When and why does fragmentation occur in IPv6?

A

At the client when the packet is greater than the MTU.

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10
Q

What is the MTU?

A

Maximum Transmission Unit

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11
Q

What are the security issues of IPv6?

A

Privacy issues when using MAC address (basis) to generate IPv6 addresses.
Sheer number can make scanning less feasible.
Undiscovered flaws.
Transition mechanisms can bypass network security.

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12
Q

Why is the network layer unreliable?

A

It is connectionless (reliablity dealt with by Transport layer).

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13
Q

What can be done to ease traffic?

A 
Splitting into subnets to reduce global traffic.
Using ARP (sending some requests over the link layer only).
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14
Q

What are IPv4 subnets?

A

Logical division of a network.

Each division is localised behind a router.

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15
Q

What are the special addresses of a subnet?

A

Subnet Network address: First address
Broadcast address: Last address
Router IP address: First/last available addres

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16
Q

What is CIDR?

A

Classless Inter Domain Routing

17
Q

Which subnets size should be allocated for each situation?

Interrouting Links, Home/small business, Site

A

IRR: /127
Home/Small Business: /56
Site: /48

18
Q

What does a router do?

A

Forward IP datagrams to other LANs.

19
Q

How are loop paths prevented?

A

Using spanning trees to discard any links that create loops.

20
Q

What is the default router?

A

The router on a network that connects that network to the internet.

21
Q

What are global addresses used for?

A

Being accessible via the internet.

22
Q

What are the 2 methods for assigning global addresses for IPv4?

A

DHCP

NAT - Use one public address.

23
Q

What are the 2 methods of assigning global addreses for IPv6?

A

SLAAC - Stateless Address Auto Config : Use network prefix (64) and MAC address (64) based host part.
SIIT - Uses translated IPv4.

24
Q

What does the Border Gateway Protocol do?

A

Send packets outside the network.

25
Q

What is a distance vector protocol?

A

A type of routing protocol that uses shortest distance as metric for routes.

26
Q

What is RIP?

A

Routing Information Protocol.

Use shop count as metric.

27
Q

What is the process for RIP?

A

Maintain a routing table.
Each router sends its table to its directly connected neighbours.
If the received table has smaller distances for routes, update your own table.

28
Q

What are the limitations of RIP?

A

Max hops is 15, anything further is unreachable.
Uses UDP - can loose packets.
Routers have no knowledge of network topology.

29
Q

What is the process of link-state routing?

A 
Discover router's neighbours.
Calculate cost metric to the neighbours.
Generate a LS information packet with this information.
Flood this to all routers in the area.
Build up topology knowledge.
30
Q

What is used to find the shortest paths for a network?

A

Dijkstra’s Algorithm

31
Q

What are examples of Link State Routing?

A

Open Shortest Path First

IS-IS

Networks (4 decks)

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