IIoT (Industrial Internet of Things) follows IEEE 802.11n specification that defines the standard for Medium Access Control(MAC) and Physical (PHY) layers which supports enhanced data transmission with reduced overhead and multiple spatial stream data transmission with different data rates. The downward compatibility of 802.11n specification with 802.11b and 802.11g allows co-existence of devices with different physical layer specifications i.e Different data rates across hops over a path in non-pure 802.11n based networks. Due to the downward compatibility of 802.11n and the support for multiple radios it allows the nodes with different physical layer specifications such as 802.11b and 802.11g to send and receive data. The variation in data rate introduces several challenges to ensure QoS (Data rate, Queuing delay, Transmission delay, Bit Error Rate and Jitter) guaranteed transmission of multimedia content. We analyse such a non-pure 802.11n network with different data rate and propose Multi Metric based Routing protocol for streaming QoS guaranteed multimedia over non pure 802.11n based network. Multi metric refers to transmission delay, buffer size and buffer service rate at each node. We propose a system model to represent the scenario and analyse the benefits through simulation in MATLAB. In contrast to COARP (Cache Optimized Adaptive routing Protocol) a well-known approach to predict path in pure 802.11n, we consider non pure 802.11n which consists of nodes with different physical layer specifications such as 802.11b and 802.11g. In addition we consider buffer servicing rate at each node. We evaluate the performance of the proposed algorithm in identifying and calculating path metrics such as data rate, queuing delay and jitter for supporting QoS guaranteed transmission in non-pure 802.11n network. We prove the efficiency of the proposed algorithm in finding a route that satisfies the QoS requirements of multimedia data in heterogeneous physical layer scenario and nodes with different queue servicing rate compared to the COARP that considers only pure 802.11n. © 2019, Research Trend. All rights reserved.