You are the network administrator of an enterprise with a main site and multiple remote sites. Your network carries both VOIP and data traffic. You agree with your service provider to classify VOIP…

Question

Options

• Adata marked with DSCP AF21, VOIP marked with DSCP EF
• Bdata marked with DSCP AF51, VOIP marked with DSCP EF
• Cdata marked with the DE-bit, VOIP marked with the CLP-bit
• Ddata marked with DSCP EF, VOIP marked with DSCP AF31
• Edata marked with IP precedence 5, VOIP marked with DSCP EF

• A
  90% (27)
• C
  7% (2)
• E
  3% (1)

Explanation

RFC 4594 ('Configuration Guidelines for DiffServ Service Classes') defines the standard per-hop behaviors for traffic classification. VoIP bearer (real-time) traffic should be marked with DSCP EF (Expedited Forwarding, value 46), which guarantees low latency, low jitter, and low loss - defined in RFC 3246. Standard data traffic is typically marked with DSCP AF21 (Assured Forwarding class 2, drop precedence 1), which provides a committed rate with some protection against drops. (B) is wrong because AF51 does not exist - the AF classes only go from AF11 to AF43. (D) is wrong because EF is reserved for real-time traffic, not data. (E) is wrong because IP Precedence 5 and DSCP EF are not the same, and mixing marking schemes is non-standard.

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