Two MPLS Label Characteristics

CD.

Sure, I can explain the two MPLS label characteristics that are correct.

A) The label edge router swaps labels on the received packets: MPLS (Multiprotocol Label Switching) is a technology that enables the forwarding of packets based on labels instead of IP addresses. Label Edge Router (LER) is a device that attaches an MPLS label to incoming packets and forwards them into the MPLS network. When the labeled packet reaches another LER, it removes the existing label and adds a new label to the packet before forwarding it to the next hop. This process is called "label swapping," and it occurs at each LER as the packet traverses the MPLS network. Therefore, the correct answer is A.

B) An MPLS label is a short identifier that identifies a forwarding equivalence class: An MPLS label is a 32-bit identifier that is attached to a packet to identify the packet's forwarding path through the network. The MPLS label is inserted between the Layer 2 and Layer 3 headers of the packet, creating an MPLS header. This MPLS header is used by the MPLS routers to switch packets through the network based on the label, rather than performing a lookup on the destination IP address. The MPLS label represents a Forwarding Equivalence Class (FEC), which is a group of packets that are forwarded in the same way through the network. Therefore, the correct answer is D.

C) LDP uses TCP for reliable delivery of information: Label Distribution Protocol (LDP) is a protocol used to distribute labels in an MPLS network. LDP uses the TCP protocol for reliable delivery of information between LDP peers. However, this is not a label characteristic, and therefore the answer is incorrect.

E) A maximum of two labels can be imposed on an MPLS packet: MPLS supports the imposition of multiple labels on a packet. In fact, the number of labels that can be imposed on a packet is not limited, and it depends on the network requirements and the number of MPLS labels that are configured on the routers. Therefore, the answer is incorrect.

In summary, the two MPLS label characteristics are:

• The label edge router swaps labels on the received packets.
• An MPLS label is a short identifier that identifies a forwarding equivalence class.