Psychz - Sharad
Votes: 0Posted On: Apr 07, 2017 11:30:28
Networking is all about the flow of data which is generally referred as network traffic. Large amounts of data flow in the network fragmented in small pieces called packets. Just like a river, a network also has “Upstream” and “Downstream” which mean the data would be following in a similar way. However, a direct comparison would incorrect because when applying these terms to networks, it is important to understand that it is all about perspective.
Understanding the intended perspective may be the most challenging aspect to understand the intent of the entity delivering the message.
The term “Upstream” and “Downstream” are very relative in its roots. Consider yourself throwing a ball to your friend. For you the ball is moving away from you, however, for your friend the ball is moving towards him. You can consider the ball moving upstream, whereas for your friend the ball is moving downstream. Similarly, in a network, upstream data for one device could be downstream for another device. The data packets are bidirectional in nature. The packets keep “flowing” in the network between two or more points. The packets sent by one network are the packets received by another. Consider yourself downloading a file from a device. The packets you download will be travelling downstream in relation to you. But with respect to the device it would be sending data upstream.
To make you understand this better let us discuss scenarios where the movement is actually happening
Server-Client Relation
The server-client relation refers to the connectivity between the server and client. The remote hosts called clients located at one part of the world can access and indulge in data transfer to and from the servers that are situated at large distances from them.
Imagine downloading files such as images, videos or mail on a daily basis from your preferred websites. These websites are hosted on a server located somewhere distant. Now, these files travel through the network in the form of packets. When you are extracting something from the server it is generally referred to a downloading or downstream traffic. On the other hand, if you are sending data to the server it is referred to as uploading or upstream traffic. In case of Server-Client paradigm, the terms “Upstream” and “Downstream” are used only with respect to the server.
Network Devices
Another way of looking at upstream and downstream is with reference to the network devices. There are a lot of network devices connected to each other in a network. The networks can be as complex as thousands of routers and switches or as basic as two computers. In a network, the terms upstream and downstream are used with respect to the position of the devices.
For instance, the flow of packets between three kinds of switches: access, distribution and core switches. The flow of packets from the access switches to the distribution and core switches is upstream. Whereas, from core level switches to access switches, the flow of packets is downstream traffic. With respect to distribution switches, the flow of packets to core switches is upstream traffic while the flow to access switches is downstream traffic.
Internet Service Providers (ISPs)
In the perspective of ISPs the upstream and downstream traffic is referred to the data coming in or going out of their network. If a user sends the data to another user belonging to some other ISP, then it is considered as downstream traffic. Whereas, if the data is coming from a user that belongs to other ISP, it is called upstream traffic.
The ambiguity pertaining to these terminologies will remain to most of the internet users. However, it is rarely used by general public. They are important to network administrators, who monitor the bandwidth usage of networks and individual systems.
