Networks Flashcards
Describe client-server networking
Most computers are nominated as clients and one or more as servers. The clients request services from the servers.
name an advantage of client-server networking
-Efficient allocation of resources
Name a disadvantage of client-server networking
-A single server is a point of failure
What is included in a network access device (router/gateway)?
- WAP (wireless access point)
- Switch
- Router
- Modem (sometimes)
What is a WAN?
A WAN (Wide Area Network) is a telecommunications network that extends over a large geographic area for the primary purpose of computer networking.
Why are WANs no longer used?
Companies use VPNs and connect over the internet because it is cheaper.
What is data sent through the internet in?
Packets
What is connectionless communication?
Connectionless communication is a data transmission method used in packet switching networks in which each data unit is individually addressed and routed based on information carried in each unit.
Which packets are directed to the WAN interface and which are directed to the LAN interface?
All packets that are not for the local network are directed to the WAN interface.
How does the router decide on where to send a packet?
It uses a routing table to determine the best next hop for the packet.
What happens if part of the communications infrastructure fails?
The router chooses a different route and subsequent packets may be sent over a different path.
What happens if the router is too busy?
The packets are buffered in memory, causing high latency.
What happens if a router runs out of memory?
The incoming packets are discarded and they will need to be resent.
What happens if a packet contains a ToS (Type of Service) field in the packet header?
The packet is placed at a higher priority level and gets placed at the front of the queue of packets to be routed.
What is a TTL?
A TTL (Time to Live) determines how long a packet could loop between routers before being discarded.
What are the components of a packet?
Packets contain:
- Sender’s IP address
- Recipient’s IP address
- Protocol used
- Packet sequence number
- Payload (the data)
- Checksum
What is a router?
A router is a networking device that forwards data packets between computer networks.
What is a gateway?
A gateway is a hardware device that acts as a “gate” between two networks. This can be a router, firewall or server.
How is routing achieved?
The router receives a packet, the router calculates the optimal hop to the next router, then the packet is sent to that router.
How can a firewall be implemented?
A firewall can be implemented in hardware, software or a combination of both.
How does static filtering work?
A firewall will check the headers of packets against a set of rules or ‘packet filters’ defined by the network administrator.
What does the packet header field include?
- Source IP address
- Destination IP address
- Port number
- Protocol
Give an example of a commonly blocked protocol
SSH (secure shell) headers are typically blocked as they are used to remotely manage computers.
How does stateful inspection work?
Stateful inspection continuously monitors incoming and outgoing traffic after a connection is established, analysing packet types and looking inside the payload of the packet as well as the header.
