our networks run at a predefined speed for example a 1,00 Bas T gigabit Network operates and sends traffic at 1 gbit per second this network cannot pass traffic faster than 1 gabit per second but what if you have multiple 1 gig links plugged into a switch and both of those connections are sending traffic at 1 gbit per second to the same destination obviously we can't fit 2 gbits per second into a 1 gabit per second link and in those cases we run into congestion this contention of both networks trying to send information at the same time we'll certainly queue up some packets into a buffer but eventually we will fill up that buffer and have congestion these buffers that are in a switch or a router are relatively small and they're not going to hold a lot of packets So eventually packets are going to need to be discarded so that we can keep the system running this means that we're going to lose information that we're sending between one station and another so to resolve that we will need to either increase the size and speed of the network or we will need to decrease the amount of traffic that's going over that Network often people will say the network is slow and what they're really saying is that there's some type of bottleneck on the network that is causing a Slowdown unfortunately this can be very difficult to troubleshoot because the problem might be with a number of different Technologies it might be related to the bus of the system that you're you're using maybe the speed of a CPU inside of a switch or a router perhaps you're using a hard drive or an SSD which would be very different in the speeds of that storage drive and of course we have different networks with different speeds that are sent across different locations we have to look at all of these different parameters between one device and another to really understand where the bottlenecks might be on a network sometimes it might be very obvious what's causing this bottleneck but often you need to drill down into the det details of these systems to be able to understand what resources are being used or slowing down that's causing this problem for everyone else here's an example of a web transaction response time you can see transactions on this network were running somewhere around 1500 1750 milliseconds that's almost 2 seconds of delay when somebody requested data notice that there was a lot of time that was being used by the database in this particular example it seemed obvious that our problem was somehow located in the database server itself and by making some configuration changes to this database server we were able to eliminate this bottleneck and you can see the response times went down to around 500 milliseconds if you want to know how much a network is being used you might want to look at the bandwidth percentage this is a measure of how much a network is being used over a particular amount of time usually this is a percentage that's being presented so that we can understand how much of this network network is in use during that time frame we might also want to measure throughput which tells us how much data we were able to move through that Network during that time frame this gives us information about what size of data we're able to move and in what time frames we're able to move it there are different ways to monitor bandwidth statistics you may be able to gather these directly from a switch or you may use SNMP or netf flow to be able to gather this over time and if you're looking at bandwidth usage over a number of different links between two devices you'll find that the slowest link is the one that probably is holding up the throughput for all of the other networks latency is calculated as the delay between the request and the response whenever we're measuring latency we want to know how fast or how slow is this transaction occurring there will always be some type of latency on a connection because it takes time to move that information from one device to another but ideally we would want to measure these respon times at every stop along the way this allows us to understand just how quickly we can move data from one segment to another and we can break it down into its smallest parts to get a true measurement of this we would need some type of measuring tool in every single Network link along that path so this could be rather involved to be able to set up all of those devices but once you do you'll be able to capture the packets and determine what the true latency is of that connection because you're capturing packets you have microsc granularity so you're able to know exactly how long a packet stayed in a device how long it took to Traverse that Network and how long it took to forward to the next segment one of the problems a network administrator would like to avoid is packet loss if we're sending traffic across the network the ideal situation is for all of that traffic to make it across the network all of the time but there will be scenarios where that information simply can't make it across the network for one reason or another a packet loss or a discard means that there weren't any errors with the packet but some other reason caused us to discard that packet instead of sending it to its destination this may be due to an outage on the network or it could be that we have contention we simply don't have enough bandwidth to send all of that traffic across the network sometimes we're on a bad wireless network maybe we have a bad cable and the information we're sending across the network becomes corrupted when that corruption occurs during the transmission of that data it's identified when it reaches the other side and because that data is corrupted it is completely discarded and we have to resend that traffic across the network this takes additional time and resources and could cause significant delays to your application talking on a Voiceover IP phone call or watching live video streams are very sensitive to any type of delay you might put on the network we would like these packets to arrive at regular predictable intervals and as long as that's happening we can continue to have our phone call or watch our live stream and everything is working as expected but if we have congestion on the network or the packet is corrupted we have to discard that packet we can't rewind our conversation or rewind the live stream we simply have to discard that packet and continue forward this might cause a delay or a clicking noise on the phone call or we might see a small stutter on our live stream to be able to see if we're receiving frames at regular intervals we can measure the Jitter on the network Jitter is the time between those frames and we would like that Jitter value to be a consistent value all the time this is what we would like to see which has a relatively small amount of Jitter because there's a small amount of delay between each of these packets there is a little bit of variability between each of these packets but they are being received at regular intervals if we're having high Jitter values then we might have three of those packets come through and then a long delay and then three more packets very quickly and then another delay it's these high Jitter values that give you problems hearing on a phone call or give you that stutter during a live video feed