Frequently Asked Questions (FAQ)

1:	What is the status of the MPLS standard?
A1:	Most MPLS standards are in the "Internet Draft" phase, although several have moved into the RFC-STD (RFC Standard) phase. For more information on the current status of various Internet Drafts, see the IETF's MPLS Working Group home page at www.ietf.org/html.charters/mpls-charter.html.
2:	What other protocols does MPLS support besides IP?
A2:	By definition, MPLS supports multiple protocols. At the Network Layer, MPLS supports IPv6, IPv4, IPX (Novell), and AppleTalk. At the Link Layer MPLS supports Ethernet, Token Ring, FDDI, ATM, Frame Relay, and Point-to-Point Links. MPLS can essentially work with any control protocol other than IP and layer on top of any link layer protocol.
3:	What are the differences between MPLS and ATM?
A3:	MPLS brings the traffic engineering capabilities of ATM to packet-based networks. MPLS works by tagging IP packets with "labels" specifying route and priority. MPLS combines the scalability and flexibility of routing with performance and traffic management of Layer 2 switching and can run over nearly any transport medium, such as ATM, Frame Relay, Packet over SONET (PoS), and Ethernet.
4:	Does MPLS replace ATM?
A4:	No, MPLS does not replace ATM but rather complements it. MPLS eliminates the complexity of mapping IP addressing and routing information directly into ATM switching tables. The MPLS label-swapping idea is the same that ATM switches use to forward ATM cells.
5:	Are MPLS-VPNs secure?
A5:	VPNs are considered to be "encrypted" tunnels across a public network. Because MPLS-VPNs do not require encryption, many network engineers have expressed concern over using MPLS to tunnel non-encrypted traffic over a public IP network. There are a couple of points to consider: MPLS-VPN traffic is isolated by the use of tags, much in the same way ATM and Frame Relay PVCs are kept isolated in a public ATM/Frame Relay network. This implies that security of MPLS-VPNs is equivalent to that of Frame Relay or ATM public network services. Interception of any of these three types of traffic would require access to the service provider network. MPLS-VPNs do not prohibit security. If security is an issue, traffic can be encrypted before it is encapsulated into MPLS by using a protocol such as IPSec or SSL. Customers comfortable with carrying their traffic over public ATM or Frame Relay services should have the same level of comfort with MPLS-VPN services. Customers requiring additional security should employ encryption in addition to MPLS.
6:	What is "Generalized MPLS" or "GMPLS" (formerly MPL(ambda)S)?
A6:	Generalized MPLS extends MPLS to encompass time-division (such as SONET ADMs), wavelength (optical lambdas) and spatial switching (such as incoming port or fiber to outgoing port or fiber). GMPLS represents an extension of MPLS to enable MPLS to be used as the control mechanism for configuring both packet-based paths and paths in non-packet based devices such as optical switches, TDM muxes, and SONET/ADMs (Add/Drop Multiplexers). With GMPLS, providers can provision resources dynamically and provide the redundancy for implementing various protection and restoration techniques across the network backbone.