A method of selecting paths in a wireless process control and/or automation network, the wireless process control and/or automation network including a tier of one or more wireless end devices for transmitting data and/or receiving data, and either a tier of one or more wireless intermediate devices for transmitting data and/or receiving data and routing received data and a tier of one or more wireless gateway devices for assigning data paths, transmitting data, receiving data and routing received data, or a tier of or one or more wireless intermediate devices or a tier of one or more wireless gateway devices, wherein a source-destination pair includes links between the one or more wireless end devices, and the one or more wireless intermediate devices and/or the one or more wireless gateway devices, the method of selecting paths comprising: a. designating a maximum allowable end-to-end delay and a maximum allowable tier delay for a selected source-destination pair and for each tier for a selected source-destination pair; b. determining possible paths between the selected source-destination pair; c. calculating an end-to-end delay for one of the possible paths; d. identifying a potentially acceptable path by comparison of the calculated end-to-end delay for the one of the possible paths with the maximum allowable end-to-end delay, wherein a path is deemed potentially acceptable if the calculated end-to-end delay is equal to or less than the maximum allowable end-to-end delay; e. calculating a tier delay for a link or set of links within one of the tiers in the potentially acceptable path; f. identifying an acceptable link or set of links within that one of the tiers by comparison of the calculated tier delay for that link or set of links with the maximum allowable tier delay for that one of the tiers, wherein a link or set of links is deemed acceptable if the calculated tier delay is equal to or less than the maximum allowable tier delay for that one of the tiers; g. repeating steps (e) and (f) for a link or set of links within each tier of the potentially acceptable path; h. assigning the potentially acceptable path for the selected source-destination pair to a routing table if all of the links or sets of links within the one of the possible paths are identified as an acceptable path; and i. repeating steps (c)-(h) for each of the possible paths identified in step (b). a. designating a maximum allowable end-to-end delay and a maximum allowable tier delay for a selected source-destination pair and for each tier for a selected source-destination pair; b. determining possible paths between the selected source-destination pair; c. calculating an end-to-end delay for one of the possible paths; d. identifying a potentially acceptable path by comparison of the calculated end-to-end delay for the one of the possible paths with the maximum allowable end-to-end delay, wherein a path is deemed potentially acceptable if the calculated end-to-end delay is equal to or less than the maximum allowable end-to-end delay; e. calculating a tier delay for a link or set of links within one of the tiers in the potentially acceptable path; f. identifying an acceptable link or set of links within that one of the tiers by comparison of the calculated tier delay for that link or set of links with the maximum allowable tier delay for that one of the tiers, wherein a link or set of links is deemed acceptable if the calculated tier delay is equal to or less than the maximum allowable tier delay for that one of the tiers; g. repeating steps (e) and (f) for a link or set of links within each tier of the potentially acceptable path; h. assigning the potentially acceptable path for the selected source-destination pair to a routing table if all of the links or sets of links within the one of the possible paths are identified as an acceptable path; and i. repeating steps (c)-(h) for each of the possible paths identified in step (b).