Exam 350-801 topic 1 question 165 discussion

As Omitted explains: default for voip Dial-peer is G.729, which suits all other dial-peers have same value, but use different codecs, which consume more bandwith

The problem is, if include 802.1Q tag or not in the ethernet header. g729 Without 802.1q tag: [20 bytes(payload) +40 bytes (ipheader) + 22 bytes (ethernet)] * 50 pps * 8bits/byte = 31200 g720 with 802.1q tag [20 bytes(payload) +40 bytes (ipheader) + 22 bytes (ethernet)] * 50 pps * 8bits/byte = 32800 ILBC without 802.1Q tag: [ 38 bytes (payload) + 40 bytes (ipheader) + 18 bytes (ethernet)] * 50 pps * 8bits/byte = 38400 bps ILBC with 802.1q tag: [ 38 bytes (payload) + 40 bytes (ipheader) + 22 bytes (ethernet)] * 50 pps * 8bits/byte = 40000 bps it is there the homework, with or without 802.1q: I do not know if A or B

If the correct answer points to ILBC, shouldn't B be the correct answer?

A. is correct answer.

If you refer to Cisco's Ethernet Bandwidth table, only ilbc mode 30 would be able to run 5 concurrent calls on that link so answer should be A. As noted 5 x 31.2 = 156kb. Source: https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/7934-bwidth-consume.html

https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/7934-bwidth-consume.html G.729: 31.2×5= 156kb ilbc: 38.4×5= 192kb so its A for me

iLBC is correct and acceptable answer - The internet Low Bit Rate Codec (iLBC) is designed for narrow band speech and results in a payload bit rate of 13.33 kbits per second for 30-millisecond (ms) frames and 15.20 kbits per second for 20 ms frames. When the codec operates at block lengths of 20 ms, it produces 304 bits per block, which is packetized as defined in RFC 3952. Similarly, for block lengths of 30 ms it produces 400 bits per block, which is packetized as defined in RFC 3952. The iLBC has built-in error correction functionality to provide better performance in networks with higher packet loss mode frame_size—The iLBC operating frame mode that will be encapsulated in each packet. Valid entries are 20 (20ms frames for 15.2kbps bit rate) or 30 (30ms frames for 13.33 kbps bit rate). Default is 20

Each call must be equal or less than 32 kbps, so iLBC is the correct

mode frame_size—The iLBC operating frame mode that will be encapsulated in each packet. Valid entries are 20 (20ms frames for 15.2kbps bit rate) or 30 (30ms frames for 13.33 kbps bit rate). Default is 20.•bytes payload_size—Number of bytes in an RTP packet. For mode 20, valid values are 38 (default), 76, 114, 152, 190, and 228. For mode 30, valid values are 50(default), 100, 150, and 200