Principle of universal Multiprotocol label switching

Operators are seeking to improve service efficiency and develop advanced services through the integration of IP and optical network technologies. First, however, they need to overcome the extremely complex multi-tier architecture. That is, the IP from the third layer extends to the first layer of the optical transport layer.

Universal Multiprotocol Tag Switching (GMPLS) is designed to meet the above needs, using the same method: Under the unified control plane, let the network intelligence extend to the network edge through the network core.

The working principle of GMPLS

GMPLS is a proposed IETF standard that is still under development and is not expected to be deployed in a large scale within two years. But this is not a new technology, because it relies on the many results achieved by the development and standardization of Multiprotocol tag switching (MPLS). MPLS replaces the ATM and Frame relay devices that monitor traffic engineering, simplifying the network architecture.

MPLS improves IP scalability and quality of service by establishing a virtual tag switching path (LSP) on a network of labeled switching routers (LSR). Gmpls's improvement of MPLS is mainly to add the ability to establish a connection at the first level.

There are two ways to deploy GMPLS: The overlay model (overlay models) and the Peer-to-peer model (peer models). In the overlay model (also known as uni), the router is a client of the relative optical domain, which is only associated with the directly adjacent optical nodes. In the overlay model, the optical network, not the router, determines the actual physical light path. In the Peer-to-peer model, the IP/MPLS layer is fully equivalent to the optical transport layer. Specifically, the IP router can determine the entire path to the connection, including the path through the optical device.

Regardless of the Peer-to-peer model or the overlay model, the purpose of GMPLS is to extend the range of MPLS from the router to the light domain. In a light field, forwarding decisions are based on time slots, wavelength, or physical ports (called "implicit tags" in gmpls terminology) rather than group boundaries. GMPLS enables such cross-domain peer-to-peer functionality by supporting new LSR, including dense wavelength division multiplexing, plug-in multiplexer, and optical crossover connectors.

The most important aspect of GMPLS is that it affects the way that requests and distributes tags, allocates bandwidth, and notifies network failures. GMPLS uses Internal Gateway Protocol (IGP) extensions to support a variety of links: normal, ungrouped, and forwarding, all of which are entered into the link state database. If the nodes at both ends of the link can send and receive packets, GMPLS treats them as normal links. If not, they are not grouped links. If a LSR can create and maintain a token exchange path, it is possible to declare to IGP that the LSP is a forwarding adjacency.

The key of this method is that GMPLS defines the layered system of LSP. This enables the nesting of LSP to support the establishment of the traffic backbone. This feature is similar to the MPLS support for markup stacking, and many of the smaller LSP can be clustered into a larger LSP. Gmpls is very similar to LSP, which represents the physical path in a virtual way.

Under the layered system established by GMPLS, the LSP at the beginning and end of the packet switching node is at the bottom, from bottom to top: the LSP connected to the TDM switching node, the LSP connected to the optical wavelength switching node, and the LSP connected to the optical switching node.

GMPLS is expected to help service providers dynamically supply bandwidth and capacity, enhance network recovery capabilities, and reduce operating costs. Gmpls is also likely to bring optical VPNs to these new revenue-generating services. Another expected benefit comes from GMPLS support for open standards, which will allow operators to use the best equipment when expanding their networks.

With the increase of IP traffic and services, the demand for GMPLS will grow with the market. However, challenges remain. Manufacturers need to build business cases that support the introduction of GMPLS. If an enterprise wants maximum efficiency, it must overcome the organizational barriers that cause optical transmission to be isolated from IP management domains.