A method of measuring network performance comprising: (a) receiving a packet at a first routing device ; (b) inspecting, by the first routing device , a packet header of said packet; (c) determining, by the first routing device , if the packet is associated with a specific network service or application; (d) determining, by the first routing device , that the packet is to be selected for sampling based on the inspecting, and further based on said determining if said packet is associated with a specific network service or application; (e) sampling, by the first routing device , the packet to produce first information; (f) transmitting, by the first routing device , the first information to a measurement server ; (g) before said transmitting the packet by the first routing device , adding an additional header to the packet, wherein the additional header uniquely identifies the packet; (h) transmitting, by the first routing device , the packet towards a destination according to routing information; (i) receiving the packet at a second routing device ; (j) determining, at the second routing device , that the packet is to be sampled, wherein the determining at the second routing device that the packet is to be sampled comprises determining a value in the additional header; (k) sampling, by the second routing device , the packet to produce second information; (l) transmitting, by the second routing device , the second information to the measurement server ; (m) before transmitting, by the second routing device , the second information to the measurement server , removing the additional header associated with the specified network service or application from the packet; and (n) determining, by the measurement server , a performance measurement based on the first information and second information. (a) receiving a packet at a first routing device ; (b) inspecting, by the first routing device , a packet header of said packet; (c) determining, by the first routing device , if the packet is associated with a specific network service or application; (d) determining, by the first routing device , that the packet is to be selected for sampling based on the inspecting, and further based on said determining if said packet is associated with a specific network service or application; (e) sampling, by the first routing device , the packet to produce first information; (f) transmitting, by the first routing device , the first information to a measurement server ; (g) before said transmitting the packet by the first routing device , adding an additional header to the packet, wherein the additional header uniquely identifies the packet; (h) transmitting, by the first routing device , the packet towards a destination according to routing information; (i) receiving the packet at a second routing device ; (j) determining, at the second routing device , that the packet is to be sampled, wherein the determining at the second routing device that the packet is to be sampled comprises determining a value in the additional header; (k) sampling, by the second routing device , the packet to produce second information; (l) transmitting, by the second routing device , the second information to the measurement server ; (m) before transmitting, by the second routing device , the second information to the measurement server , removing the additional header associated with the specified network service or application from the packet; and (n) determining, by the measurement server , a performance measurement based on the first information and second information. <EOS>