Network Carriers and business organizations are constantly seeking new ways to scale up and improve their service abilities. GMPLS is one such technology that has emerged from the business’s need for merging the worlds of optical and IP (internet network) networking.
GMPLS or Generalized Multiprotocol Label Switching is primarily a protocol suite that extends from the larger concept of MPLS in order to manage more classes of interfaces as well as switching technologies. These can include Layer-2 switching, time-division multiplexing, fiber switching, wavelength switching, etc. Due to the common origin of the 2 terminologies, GMPLS vs MPLS is an oft-cited debate point.

What is MPLS & GMPLS?

At a very basic level GMPLS differs from the traditional MPLS setup because it is capable of extending support to different types of switching. In order to support these additional types of switching, GMPLS has not just added functionality but also extended certain base functions of the main MPLS. in order to understand the concept of GMPLS and MPLS, it is important to first get to know these two terminologies function.

How Does MPLS Work?

MPLS is designed to bring in the speed of a layer 2 switching to a layer 3 network. Further, this technology also helps resolve the issues of IP (internet protocol) over ATM (asynchronous transfer mode). These issues can be related to the scalability or complexity of management and control. But most importantly, MPLS is capable of supporting various layer 2 technologies. It is important to note that based on the labels, the data packets are ‘switched’ and not routed.

Benefits of MPLS

MPLS is extremely popular as it is able to take into consideration QoS (Quality of Service) attributes while assigning traffic. The technology works with the label system, thereby, allowing clients to determine the prioritization levels.

Secondly, MPLS traffic is far more efficient and intelligent than any other traditional networking method. The setup is scalable as well as affordable as you can incorporate different low-cost network connections while still achieving smooth traffic flow.

How Does GMPLS Work?

GMPLS is the next step of MPLS technology. As the name suggests, GMPLS ‘generalizes’ MPLS by defining the labels for switching different types of Layer 1, 2, or 3 traffic. This is because the nodes in this technology are capable of having links with different switching capabilities including FSC (Fiber-switched capable), LSC (Lambda-switched capable), PSC (packet-switched capable), and TSC (Time-division Multiplexing switched-capable). However, the LSCs or label switched paths must begin and end on links having the same switching capability. This extension allows the technology to include a vast number of devices that can be included in label switching.


The generalization of MPLS for supporting circuit-switched and optical networks is not an easy one to execute. Therefore, GMPLS is the perfect answer that offers a control solution based on IP to dynamically drive such a network that can still be managed by centralized traffic engineering tools.

Benefits of GMPLS

One of the most prominent benefits of GMPLS is that it allows the participation of Layer 3 devices within the signaling circuits. These devices stand to benefit from path protection as well as the reestablishment of MPLS within the circuit. The technology is created to bring together the infrastructure and traditional transport with the internet protocol layer. GMPLS, essentially, extends the network intelligence from the network edge to the core and then back to the network edge. And it performs all this under a unified control plane.

Understanding MPLS and GMPLS Routing and Signaling Protocols

MPLS improves the quality of service and IP scalability by creating virtual LSPs or label-switched paths, across a network of label switching routers or LSRs. GMPLS’s main contribution or enhancement to MPLS is seen in its ability at establishing connections in layer 1 as well. MPLS only defines the forwarding mechanisms; it actually uses completely other protocols for establishing the LSPs. Therefore, 2 different protocols are required to perform this activity – a routing protocol and separate signaling protocol.

Routing Protocols

Routing protocols are responsible for distributing information pertaining to network topology all through the network. This is done to ensure that the route of the LSP can be automatically calculated. Interior gateways like IS-IS (Intermediate System to Intermediate System) or OSPF (Open Shortest Path First) are usually used in the case of MPLS since MPLS networks are normally designed to cover a single administrative domain. Although, it is important to note that these routing protocols are only programmed to distribute network topology. You will be required to use traffic engineering extensions to these protocols if you require traffic engineering in order to establish LSPs with assured QoS characteristics and also backup LSPs for avoiding any one single point of failure.

Signaling Protocols

The signaling protocols in MPLS and GMPLS inform the switches along the route as to which links and labels to be used for each LSP. This particular information is then used for programming the switching fabric.
Depending on the application, MPLS mainly uses LDP for transport where traffic engineering is not required. MPLS also uses RSVP-TE (Resource Reservation Protocol with Traffic Engineering) where traffic engineering is required. MPLS also uses BGP as a signaling protocol for specific services like BGP/MPLS layer 3 VPN environments.
GMPLS set up consists of 3 main protocols including, RSVP-TE, OSPF-TE, and LMP (link management protocol).

The Major Differences Between GMPLS and MPLS

GMPLS vs MPLS is a rational debate, especially if organizations are trying to decide between the two or if they are looking at upgrading from MPLS to GMPLS. At the surface, there may not seem any substantial differences between the two. However, having understood what each technology stands for, we are now in a better position to highlight the key areas where there 2 differentiate from each other.

  1. The difference in handling data and control planes is often cited in a GMPLS vs MPLS debate. With regard to data and control planes, they are the same channel in an MPLS environment. However, the data and control plans in a GMPLS setup is a dedicated signaling channel or channels.

  2. Secondly, GMPLS supports various types of interfaces including PSC, L2SC, TDM, LSC, and FSC. MPLS only supports cell or frame (L2SC) and Packet-based (PSC). This is another one of the core differences between the 2 technologies and highlights GMPLS’s enhanced capabilities over a traditional MPLS setup.

  3. GMPLS is bidirectional, however, the network packets have to flow on the same type of interfaces at both ends. MPLS, on the other hand, is entirely unidirectional and is label defined.

  4. Talking of labels, MPLS supports a unique label format. It is also one of its distinguishing characteristics. The label format in GMPLS depends solely on the interface type. In other words, it is a more generalized label concept when compared to the handling of labels in MPLS.

  5. Label processing in GMPLS is only used in the control plane in LSC, FSC, TDM. In MPLS, label processing is used in the data plane for packet forwarding and in the control plane for executing an LSP setup.

  6. With respect to label restrictions in GMPLS, upstream can restrict labels that are used in the path and suggest labels as well. Whereas, in MPLS, there are absolutely no constraints with respect to label allocation and there are no label suggestions as well to the downstream nodes.

  7. MPLS works on a continuous bandwidth allocation. GMPLS, on the other hand, functions on a discreet bandwidth allocation. While this may not be a critical difference, it is still a significant point of distinction in a GMPLS vs MPLS discussion.

  8. With respect to signaling awareness of the physical layer, the label packets are presumed in MPLS. In GMPLS, it is media-specific signaling..

  9. MPLS contains fewer parallel links and there are many labels per link. GMPL is capable of including hundreds of parallel links including link bundling and common labels.

  10. Fault notification in MPLS is purely in-band. In GMPLS, fault notification is in-band, i.e. a failure in the control plane, and out-of-band, i.e. data plane failure.

  11. No LSP protection information is conveyed in an MPLS environment. GMPLS setup is capable of indicating the LSP link protection type. All link protection capabilities in GMPLS are advertised by means of routing.

In Conclusion

The demand for GMPLS has grown as IP traffic and IP services have increased all over the world. This technology has proven its potential by helping service providers dynamically provision capacity and bandwidth while improving their abilities to restore the network. Overall, GMPLS has further helped in reducing the operating expenditure. Having said that, MPLS is still as relevant as it was a decade back and the introduction of GMPLS is in no way a threat to its existence. Depending on your business and application requirements, our experts at CarrierBid can help you decide which network technology is more applicable to your environment. You can reach us directly or fill in the form below with your details and we will connect with you for an initial consultation. Our services are completely free of charge so we can be a “risk-free” addition to your IT team.

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