CCNA R&S Article #2 – Networking Model
CCNA R&S Article #2-Networking Model
Today let’s talk about Networking Models – we’ll talk briefly about TCP/IP Networking ModelHave you ever thought about how networking equipment from
different vendors are able to talk to each other? I mean a Laptop from HP is
connecting to Wireless Modem installed by your Internet service provider manufactured
by some other company.
Networks work perfectly because they speak the common
language or follow the same rules. These common rules are defined as standards
and protocols. These standards are defined as network models. You can think of these
models as a blueprint for designing the network. Different networking companies
follow these blueprints during their product development. The final devices in a
network will function because follows the standard reference model or blueprint.
I hope you are with me and got a broad idea of why a network
model is required in the real world. Now let’s talk about the TCP/IP Networking
model. It is a pervasively used networking model in use.
Networking Model
The networking model is also known as the networking blueprint. It can be said to be a detailed document covering all aspects of the network. You can think of Reference Model as multiple blueprint documents that are used when building a house.
Everyone who is contributing to building the house with all facility whether it is an architect, electrician, carpenter, or plumber refer to the same document so that they build a house as it was outlined in the blueprint. Similarly, the network model breaks the functions into smaller categories called layers. Each layer contains the related protocols and standards.
Different companies build their products and follow the respective
layer. It ensures that the newly developed product does not cause any problems
with the already running network with other devices. This makes their product
compatible with others in the production environment.
Evolution of the Networking Model
Initially, when there was no Networking Model to refer each OEM
had its own proprietary networking model. Here I am talking about the 1970s
scenario. As you can imagine there used to be different networks talking to devices
from the same OEMs. The network team used to manage this different network separately.
Back in the 1980s International Organization for
Standardization (ISO) started to work on a project to standardize the
networking protocols to allow interoperability across the globe. This work is known
as Open System Interconnect (OSI) networking model.
In parallel, open and less-formal vendor-neutral, the project
was started by the US Department of Defense (DoD). Further, more volunteered researchers
at various universities joined and contributed to the efforts of DoD – and TCP/IP
networking model shaped up.
Initially, companies used both OSI & TCP/IP protocols together
in their networking development. However, by the end of the 1990s, TCP/IP
dominated and become the common choice.
TCP/IP Networking Model
The TCP/IP network model defines the protocols at various
layers that allow devices to communicate. TCP/IP uses the documents called
Request for Comments. These RFC documents highlight the protocols and their
implementation in detail.
Any device that is powered on and connected through the right
cable to a network will communicate with other devices on the network. This is because
the company that manufactured the device, implemented the TCP/IP functionality
when building the device.
TCP/IP breaks the networking functions into multiple layers
to understand the networking function.
Figure 1: TCP/IP Networking Model
The top 2 layers (Application and Transport) focus on the
applications that need to send and receive data. The bottom layers (Network,
Data-link, and Physical Layer) focus on how to transfer bits over individual
links. In this layered approach, each layer provides the services to the layer just
above that.
- Application Layer – defines protocols that provide services to the applications running on a device.
- Transport Layer – provides services to the application layer protocols like error recovery, end-to-end same-layer interaction, etc.
- Network Layer – includes one major protocol: Internet Protocol(IP). IP provides features like addressing and routing for packets in a
network.
- Data-Link & Physical Layer – both work closely and defines the protocols and hardware to deliver the data across the physical network. The physical layer defines cabling and energy flow over physical cable. As you know the network layer is more on the routing, data-link information is used by the network layer to perform the packet forwarding to the next-hop device.
I hope you find this informative. See you soon with detailed information on TCP/IP networking model.
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