This page provides different sort of data analysis using ping and traceroute data.
Goals
To find the minimum buffer size along a network path.
To utilise existing measurements if they already exist.
Non-goals (at this time)
To determine where the bottleneck queuesize exists in a network path.
To deploy new measurement infrastructures.
Delays:
There are three types of delays a packet can have during its transmission from source to destination.
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Yee: Maybe specify:
- Propagation Delay (T _ p ): The time it takes for a packet to transfer across the network path when the queuing and transmission delays are zero.
- Transmission Delay (T _ d ): The time it takes for a packet to be processed and transfered through the network nodes.
- Queuing Delay (T _ q ): Variation in the end-to-end delay because the packet had to be serviced by deviced due to queuing.
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As such, the one way latency along a network path is composed of
T = T _ p + T _ d + T _ q
Bearing in mind that the transmission and queuing delays may be at both ends of the peer link, for a single hop, we have
T _ i = T _ p + ( T _d)_i di + ( T _d)_i di+1 + ( T _q)_i qi + ( T _q)_i qi+1
And the complete end-to-end one way latency is defined as
T = Sum _ n i of T _ i
where n is the total number of nodes along a route.
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Let's say, we have to find minimum buffer sizes along the path. Practically, it is very difficult to measure the exact buffer size of each hop along the path. We can somehow easily estimate the queing delay along the path using ping and traceroute tools. From queing delay, we can estimate congestion, buffer overflow, incoming and outgoing data rate. If we take the difference of incoming and outgoing datarate that will give us the queue occupancy. From queue occupancy, we can roughly estimate the buffer size of that specific router. In the following sections, I am going to explain how we can measure the average queing delay using ping, and queing delay at each and every hop along the path using traceroute.
Ping and Delays:
In a network world, ping basically helps us to measure round trip time(RTT) from source to destination using ICMP Echo Messages. It doesn't provide, what path the packet takes to each router and the no. of routers the packet have traversed. Normally network engineers provides the no. of attempts e.g. 10 in PingER for each probe. From these 10 attempts, they measure four or five different metrics. Min Rtt, Max RTT, Avr RTT, Packet loss and sometimes the standard deviation of the RTTs. Using these metrics, we can measure the average queing delay along the whole path by subtracting MaxRTT from MinRTT.
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It is practically, impossible to get a very good estimate of Queing delay at each hop along the path using ping. Yee: Why???
Traceroute and Delays:
The default traceroute basically provides us with following metrics:
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