MPLS Label for Egress Router
Question
Your RSVP network is being designed to support end-to-end class of service (CoS) using best practices.
Which MPLS label should be advertised by the egress router in this situation?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.A
MPLS label 0, or explicit null, should be used so that the label is popped at the egress router.
In an RSVP (Resource Reservation Protocol) enabled network, the egress router advertises a specific MPLS (Multiprotocol Label Switching) label to indicate the requested class of service (CoS) for a particular traffic flow. This label is used by the RSVP signaling messages to reserve resources and establish end-to-end QoS for the traffic flow.
To answer the question, we need to understand the MPLS labels used in RSVP networks for QoS. In general, there are four types of MPLS labels used for QoS:
Label 0: This is the default label and is used for best-effort traffic. No QoS is applied to traffic with this label.
Label 1: This is the label used for traffic with the Expedited Forwarding (EF) PHB (Per-Hop Behavior), which provides low-latency, low-jitter, and assured bandwidth for delay-sensitive traffic such as VoIP.
Label 2: This is the label used for traffic with the Assured Forwarding (AF) PHB, which provides a differentiated level of service for traffic based on four classes (AF1 through AF4) with different drop priorities.
Label 3: This is the label used for traffic with the Best Effort PHB, which provides no guarantee of service, but is used for traffic that does not require QoS.
Based on the above information, we can conclude that the correct answer is either B or C, depending on the specific QoS requirements of the traffic flow.
If the traffic flow requires the EF PHB, which is often used for real-time applications such as VoIP, then the egress router should advertise MPLS label 1. This will ensure that the traffic is given priority treatment throughout the network and is delivered with low latency and low jitter.
If the traffic flow requires the AF PHB, which is often used for different classes of traffic that require different levels of service, then the egress router should advertise MPLS label 2. This will ensure that the traffic is given the appropriate level of service based on its class.
In general, it is best practice to use the appropriate MPLS label based on the specific QoS requirements of the traffic flow to ensure that end-to-end QoS is achieved.
