Data Analysis

This page provides different sort of data analysis using ping and traceroute data.

Delays:

There are three types of delays a packet can have during its transmission from source to destination.

1. Propagation delay(PD): A time required to send a single bit from one hop to another along the path.
2. Transmission delay(TD): A time required to transmit whole packet from a hop along the outgoing link.
3. Queing delay(QD): A time required by the packet to wait in the buffer before being ready for transmission into an outgoing link.

Total delay is the sum of all PD,TD and QD along the path. Round trip time(RTT) is equal to 2 * total delay, considering reverse path takes the same route and delays. Note: PD is normally taken as 0, compared to other delays.

Lets 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 different metrics. Min Rtt, Max RTT, Avr RTT and Packet loss. Using these metrics, we can measure the average queing delay along the whole path by subtracting MaxRTT from MinRTT.

Lets L = size of the packet and R = data rate of the whole path.   

Average QD= MaxRTT - MinRTT.

Average TD = L/R

It is practically, impossible to get a very good estimate of Queing delay at each hop along the path using ping.

Traceroute and Delays:

 Traceroute basically provides us with following metrics:

1. No. of hops from source to destination
2. IP and names of hops.
3. Three times measured RTTs from source to each hop along the path.

In my own personal point of view, we can measure a good estimate of buffer size at each hop using traceroute measurement. The following sections describe the steps to figure out estimate of buffer size at each hop.

Lets say we have two hops(R1,R2) between source A and destination B.  Traceroute measure three different RTts from A to R1 and R2 respectively. and lets denote those rtts by (RTT1, RTT2, RTT3) for R1 and (RTT1, RTT2,RTT3) for R2

Now get the Max and min rtt from the two sets separately. and denote it minRTT1, maxRTT1 for R1 and minRTT2 and maxRTT2 for R2.
It is simple to find queing delay at R1 which is:
Queing Delay at R1 (QD1) = maxRTT1 - minRTT1

As the packet goes, the latency from A to R2 is mainly affected by the queing delay of R1.  Hence we need to subtract the queing delay at R1 from the difference of maxRTT2 and minRTT2.
Queing Delay at R2 (Qd2) = maxRTT2 - minRTT2 - Qd1
 Hence, Queing Delay of nth hop router (Rn) is given below: