Page 15 - EngineerIt January 2021

IoT

protocol, performs end-to-end error checking of
data transmission for reliable and sequential Transport Control Protocol/Internet
exchange of data.
Back in the 1970s, when the protocol was Protocol (TCP/IP)
invented, latency wasn’t an issue, but that’s all
changed now, and the protocol itself is a limiting In terms of the Open Systems Interconnection model, IP is a low level protocol
factor. Keep in mind that while the primary job of on which TCP is built. The most important aspect of IP is that it provides a
the internet’s routers and that of your ISP is to mechanism for addressing network nodes, for splitting data into packets and
route IP packets, it’s the end-user’s devices and appending addresses to these packets.
applications and content providers’ servers that Being connectionless, IP does not take into consideration the failure
choose to use a protocol (TCP) that now to deliver packets. However, TCP addresses this by managing, organising
constrains throughput performance to levels and auditing all packets. To demonstrate this technique, consider the
lower than the link capacity. There is nothing your following scenario:
ISP can do to fix this. A file is transmitted as 90 packets of data, numbered sequentially
1,2,3 ... 88,89,90. During its transmission, the 45th packet is temporarily
Bigger highway, but the same car stored at a node which loses power and shuts down. This causes the
Think of it this way. Your car is constrained destination device to receive all packets except the 45th.
through its design, aerodynamics and engine TCP is responsible for re-ordering the received packets to match the
performance to achieving a top speed of say, order in which they were sent. It therefore discovers the missing 45th packet.
200 km/h when driving down a road with a TCP then requests that the packet be resent. When the 45th packet finally
single lane. If we now upgrade that same road arrives at the destination, the document is re-assembled, and its transmission
to four lanes, can your car now do 800 km/h? is complete. n
No. It can still only achieve 200 km/h.
But you can now have four cars, each driving at
200 km/h driving down the road at the same
time. The same situation occurs over fast
internet links.
Most consumers are totally unaware of the
above factors and do not understand that the
‘results’ they get when using one of the many
speed testing websites, will vary significantly
based on server selection, the mathematical
algorithm, process and protocol used to
calculate the speed, browser or app technology
being used. It is important that internet users
have at least a basic understanding of these
factors, instead of reading too much into speed
tests, which will almost always be misleading
and inaccurate.

So, is there even any point in getting a
higher capacity fibre link?
Actually yes! Many applications establish multiple
concurrent connections to get round the
limitations of the TCP/IP protocol. YouTube, for
example, fires up 12 connections when you click
on a video. As the number of user devices and
use cases just keeps on increasing over time,
links eventually become congested at certain
times of the day and then users start
experiencing the effects, such as video quality
degradation or buffering, slow browsing or
downloading, and more.
On higher capacity links however,
applications are much more responsive as they
don’t step on one another and users can
complete certain activities without having to wait
as long as they would otherwise have to. n

For more information visit www.vox.co.za

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