a. Show the layered protocol architecture (i.e., how you would represent them using OSI layers) of both the Voice over IP (VoIP) phone, the router, the Ethernet switch and the SIP server. Note the following: Assume the VoIP phone is a regular host, just like a desktop computer. Make sure to show the peer interfaces between all devices. cosce EO Router E1 Ethernet switch SIP SIP Proxy A b. Assume the information is a 500-byte Session Initiation Protocol INVITE Request to initiate a call (SIP is an Application Layer protocol) generated by the VoIP phone. It is carried over Transmission Control Protocol (TCP). How does the Layer 2 frame look like at the router's EO interface? Please draw the frame showing all the sizes. Assume the following protocol headers are used: TCP header= 20 bytes IP header = 20 bytes Ethernet header = 14 bytes