3 - Network Performance

• Computing
• Further Education (Key Stage 5)

Network Performance

Network Topologies

In networking, topology refers to the physical or logical arrangement of devices in a network. It describes the way in which devices, such as computers, servers, routers, switches, and other network components, are connected to each other and how they communicate and exchange data.

What are the different Topologies?

Star Topology

What is a 'Star' Topology?

A star network (probably the most commonly used today) has a central computer or server that is directly connected to all workstations, while each workstation is connected indirectly to every other through the central computer.

Mesh Topology

What is a 'Mesh' Topology?

In a mesh topology, devices are connected to each other in a complex, interconnected network. Data can be transmitted between devices in multiple paths, making the network highly resilient and fault-tolerant.

What is a Network Topology?

Privately owned network environment

Small geographical area

Large geographical area

WAN

LAN

Leased Lines 

Used at homes

Used in businesses with many sites.

Uses VPN's for secure connectivity.

Can devices communicate directly with each other in a 'Star' topology?

1. No, all communication goes through the central hub or switch
2. Yes, devices can communicate directly with each other
3. Yes, but only if they are connected to the same central hub or switch
4. It depends on the type of devices being used

What is the advantage of a Mesh Topology?

1. Easy to set up
2. Requires less cabling
3. No single point of failure
4. Highly reliable and fault-tolerant

Bandwidth

• Bandwidth is the amount of data that can be moved from one point to another in a given time. Higher bandwidth = more data per second
  

• The greater your bandwidth the more devices you can have connected at the same time. 

• Netflix would use a high amount of Bandwith while reading the school website would use a small amount. 

How much Bandwith would the following activity use?
Reading a news article.

1. Light
2. Medium
3. High

How much Bandwith would the following use?

A vlogger uploading videos to YouTube daily

1. Light
2. Medium
3. High

How much Bandwith would the following use?

Using social media

1. Light
2. Medium
3. High

Measuring bandwidth

• Bandwidth is measured in bits per second.

• Data transfer rates are now so good that bandwidth is usually measured in Megabits per second (Mbps)

Which do you think has the highest bandwidth?

1. 4G
2. 3G
3. Bluetooth
4. 5G

Bandwidth compared

The typical download speeds are:

• 3G: 3 Mbps
  
• 4G: 20 Mbps
  
• Broadband: 46 Mbps
  

• We have 2 kinds of speed, download speed and upload speed. 

Upload speeds are always slower than download speeds.

Why might this be the case?

The majority of the spectrum is allocated to downstream traffic to maximize download speeds. In many broadband technologies, users share bandwidth within a local network segment, prioritizing download speeds over upload speeds to prevent congestion. Asymmetric networks are less expensive to deploy and maintain, allowing ISPs to offer competitive pricing. Businesses often require symmetrical connections for higher upload speeds. Overall, most residential internet connections have slower upload speeds due to network design choices, consumer demand, and technical limitations.

Answer:

• Internet service providers (ISPs) configure our connection based on the most popular activities.

• Most users spend much more time downloading than they do uploading.

 

Test the performance of the schools connection.
Look at your download speed
Look at your upload speed. You can go online to www.speedtest.net to do this

What does this symbol mean?

Answer: Buffering

• Data is arriving at your device at a rate that is slower than it is being processed.
• Example: when you are watching a film on Netflix and it pauses, and you have to wait for a period of time before it starts again

Why do we use Subnetting?

Subnetting segregates the network into smaller, discrete segments, reducing the overall broadcast traffic within each subnet. This strategy limits the number of devices competing for bandwidth, potentially decreasing network congestion and improving performance during periods of high user activity.

Network segregation, reduced broadcast traffic, improved bandwidth management

Introduce the concept of subnetting and explain how it can be used to break down large networks

Privately owned network environment

Small geographical area

Large geographical area

WAN

LAN

Leased Lines 

Used at homes

Used in businesses with many sites.

Uses VPN's for secure connectivity.

Can devices communicate directly with each other in a 'Star' topology?

1. No, all communication goes through the central hub or switch
2. Yes, devices can communicate directly with each other
3. Yes, but only if they are connected to the same central hub or switch
4. It depends on the type of devices being used

Collision Domains

All devices interconnected by one or more hubs hear all signals generated by all other devices. 

The extent to which signals in an Ethernet bus topology network are propagated is called a collision domain.

All devices in a collision domain are subject to the possibility that whenever a device sends a frame, a collision might occur.

Broadcast Domain

A broadcast domain is a restricted area in which information can be transmitted to all devices in the domain. More specifically, Ethernet LANs are broadcast domains. Any device attached to the LAN can transmit frames to any other device because the medium is a shared transmission system. Frames are normally addressed to a specific destination device in the network. While all devices detect the frame transmission in the network, only the device to which the frame is addressed actually accepts it.

Collision Domain

A collision domain is a group of Ethernet or Fast Ethernet devices in a CSMA/CD LAN that are connected by repeaters and that compete for access in the network. Only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network to avoid data collisions. A collision domain is sometimes referred to as an Ethernet segment.

Ping (Packet Inter-Network Grouper)

Function: Ping tests the connectivity between two network devices by sending ICMP echo request packets and waiting for echo reply packets.  Measures the round-trip time and packet loss.

How to conduct a Ping test using the CLI

1. Open the command-line interface on the computer.

2. Type ping followed by a website or IP address

 eg. ping google.com

3. Analyse the output

Example

The output will show: Number of packets sent, received, and lost.  Time taken for each packet to travel to the destination and back (latency).

Here's what each part of the output means:

Pinging google.com [172.217.6.206] with 32 bytes of data: This line indicates that the host google.com is being pinged, and its IP address is 172.217.6.206. The 32 bytes of data specifies the size of the packets being sent.

Reply from 172.217.6.206: bytes=32 time=14ms TTL=53: This line indicates that a reply was received from the host 172.217.6.206. It shows the size of the packet received (bytes=32), the round-trip time it took for the packet to travel to the destination and back (time=14ms), and the Time to Live (TTL) value of the packet (TTL=53). The TTL value indicates the number of hops (routers) the packet can pass through before it's discarded.

The subsequent lines follow the same format, showing replies from the destination host with their respective round-trip times and TTL values. In this case, each reply was received successfully with low round-trip times, indicating a good connection to the destination host (google.com).

Try it yourself.

google.com.au - 172.217.3.99                                          news.com.au - 23.5.231.214

domain.com.au - 99.84.104.23                         woolworths.com.au - 13.236.63.82

realestate.com.au - 13.236.96.12                                 ebay.com.au - 66.135.211.132  seek.com.au - 52.64.36.246                                gumtree.com.au - 193.243.130.171  smh.com.au (The Sydney Morning Herald) - 104.64.221.46

abc.net.au (Australian Broadcasting Corporation) - 203.2.218.214

Traceroute

Traceroute is a network diagnostic tool used to trace the route taken by data packets to a destination. Its functions include identifying network hops, measuring latency, troubleshooting connectivity, and mapping network topology. Traceroute is valuable for diagnosing network issues, optimising performance, and understanding internet structure.

Performing a Traceroute Test

1. Open the command-line interface on the computer.

2. Type  tracert followed by a website or IP address

 eg. tracert google.com

3. Analyse the output

Explain the output:

.

Example

The output will show the path that packets take from your computer to the destination.  Each line represents a hop, showing the IP address of the device at that hop and the time it took for the packet to reach that hop.

Traceroute Command Line:

Tracing route to google.com [172.217.6.206] over a maximum of 30 hops:: This line indicates that the traceroute command is tracing the path to the destination IP address 172.217.6.206 (google.com), and it will attempt to trace up to 30 hops.

First Hop:

1 <1 ms <1 ms <1 ms 192.168.1.1: This line shows the first hop from your computer to the first device in the route, which typically is your local router. The times (<1 ms) represent the round-trip time for packets to travel to this device and back, indicating that the router is very close (usually on your local network).

Second Hop:

2 2 ms 2 ms 2 ms 10.0.0.1: The second hop is to the next device in the network path, often a device in the local ISP network or another local network device. The round-trip time here is 2 milliseconds, showing a slightly longer delay but still very fast, indicating it's nearby.

Third Hop:

3 4 ms 3 ms 3 ms 192.168.100.1: The third hop continues to another device in the network path. The times (3-4 ms) indicate a slightly longer but still relatively quick travel time, showing it’s still within a local or nearby network.

Fourth Hop (Final Destination):

4 14 ms 14 ms 13 ms 172.217.6.206: The fourth hop is the final destination, google.com, with IP address 172.217.6.206. The round-trip time is around 13-14 milliseconds, indicating that this is the time taken for the packets to reach the Google server and return.

Try it yourself.

google.com.au - 172.217.3.99                                          news.com.au - 23.5.231.214

domain.com.au - 99.84.104.23                         woolworths.com.au - 13.236.63.82

realestate.com.au - 13.236.96.12                                 ebay.com.au - 66.135.211.132  seek.com.au - 52.64.36.246                                gumtree.com.au - 193.243.130.171  smh.com.au (The Sydney Morning Herald) - 104.64.221.46

abc.net.au (Australian Broadcasting Corporation) - 203.2.218.214