By Douglas Cruz – Sales Engineer
Although MPLS is increasingly present in transport networks today, many providers (ISPs) still do not benefit from this technology that is highly widespread in the world of telecommunications (mainly in large operators).
In the universe of Brazilian providers there are ISPs in various stages of service: From small providers, which have 1,000, 2,000 ... subscribers, to providers with the size to serve tens of thousands of users offering multiple connectivity services. Each ISP has an infrastructure and equipment that allows it to operate within its own service reality, however many providers in the growth phase do not know exactly how to take the next technological step in their network.
This is the eternal dilemma of the cost-benefit balance: On the one hand, we have customers / subscribers who need high-speed connectivity, reliability for the transmission of their data and affordable prices. On the other hand, network operators who need to make more and more investments to meet these demands and at the same time having to worry about remaining competitive.
Obviously, the expansion investment in provider networks involves a multitude of themes. In this article we are going to address a technology that can directly influence the choice of your ISP's transport network elements.
Before talking about the advantages, it is worth going over some concepts about MPLS.
The “MPLS- Multi-Protocol Label Switching”, as the name implies, is a technology that involves a set of protocols that are responsible for the distribution of labels throughout a network infrastructure, making the switching of the transported services to be carried out through these labels and no longer via routes.
But what set of protocols? Well, there are several protocols that implement MPLS, the presence of the word multi-protocol refers to the capacity of integration that this technology has, since it is compatible with several layer 3 protocols, as well as the technologies involved in layer 2 (many bibliographic references position it as a layer 2.5 technology). In order not to extend too much on technical concepts, it is worth calling attention to two protocols: The infrastructure protocols responsible for defining the LSP (Label Switch Path), which is basically the way MPLS packets will travel between network elements. We are talking about LDP and RSVP. In summary, LDP aims at simplicity of network configuration and RSVP aims at analyzing bandwidth and rapid convergence in case of failures.
The combination of these multiple protocols mentioned in the paragraph above allows an MPLS infrastructure to be used to meet the main applications assigned to WAN networks. That is, through an MPLS network it is possible to create different types of VPNs (L2VPN and L3VPN), ensuring redundancy, fast convergence and optimized traffic balancing. The main services that are implemented by an MPLS network are "VPWS", "VPLS" and "L3VPN".
Service layers on top of the MPLS infrastructure
VPWS – Virtual Pseudowire Service
This service allows a point-to-point connection between sites of a given customer. VPWS has the ability to transport data transparently over the ISP's network. In practice, as there is no learning of MACs in the elements of the transport network, it is as if the provider delivered to the end customer an “ethernet cable” or an “optical fiber” emulating a dedicated connection between sites located in different regions. Some manufacturers call this technology VLL (Virtual Leased Line).
Representation of a VPWS service
VPLS – Virtual Private LAN Service
This service allows the multipoint connection between sites in a simplified way. VPLS emulates a classic L2 service transparently (TLS) to the user / subscriber. In practice, it is as if the provider delivered to the end customer an “L2 switch” with N ethernet ports for connecting multiple sites. Some manufacturers call this technology VSI (Virtual Switching Instance).
Representation of a VPLS service
L3VPN – L3 Virtual Private Network
This type of VPN allows the L3 multipoint connection between sites. L3VPN provides the sharing of services, such as the internet, as well as the isolation of traffic (Security) between different subscribers. L3VPN makes use of virtual routing tables (VRF) to emulate private IP networks. In practice, it is as if the provider delivered a “router” to the end customer, providing exclusive instances of the routing table for the service in question. Some manufacturers call this technology IPVPN.
Representation of an L3VPN service
The idea of the article is not to address the details of the technology, but to present some points to help in the following reflection: “After this explanation, should I invest in an MPLS infrastructure for my provider”? Below 5 advantages.
1. Low implementation cost
At first, comparing the value of purely L2 equipment with L3 / MPLS equipment, it may seem appropriate to choose the cheapest equipment. However, if your business is expected to grow, it is worth thinking in the medium / long term and investing in the most complete alternative.
Because it is a widespread technology, many switch / router lines bring this feature natively on the hardware, just by purchasing the software license to enable the protocols later (See MPLS DATACOM line of switches).
Think about it, for a very affordable value your network will be able to provide multiple connectivity services in a secure manner, in addition to simplifying the connection of your POPs (Points of presence).
2. No network loop problems
One fact: L2 networks are much more susceptible to loops than IP / MPLS networks. In the case of L2 networks, there are several specific protocols for preventing loops, such as xSTP, EAPS and ERPS, which can work very well depending on the size and complexity of the topology. EAPS and ERPS, for example, are protocols specifically aimed at ring topologies, but often this scenario is not reflected in the ISP's reality. Although they work very well, these L2 loop preventing protocols end up limiting the growth and performance of your network.
On the other hand, native features of an IP / MPLS network avoid loop problems without depending on a specific protocol for this. IP / MPLS networks have smaller broadcast domains and the protocols involved in the technology bring native mechanisms, such as TTL, to eliminate a possible L3 loop.
As already mentioned, it is very important to design a transport network foreseeing its evolution. The evolution of the network may undergo topological changes, so having MPLS equipment makes it easier at this point, because unlike an L2 network, MPLS can be used in the most diverse network scenarios, such as “ring”, “partial-mesh” and “full-mesh” topologies.
Another point that can interfere with the scalability of a network is the size of the routing tables for the equipment involved. In terms of tables, an L2 transport network is dependent on learning the MAC addresses of the devices connected to it, that is, the size of the MAC table of its equipment can directly interfere with the performance of its infrastructure. In an IP / MPLS network, in certain scenarios, the transport of L2 services is transparent, making it unnecessary to learn MAC on network elements, for example.
4. Traffic Engineering
In the conceptual paragraphs of MPLS, I mentioned LDP and RSVP as the protocols responsible for defining the LSP. Using RSVP it is possible to implement in your network what the market calls MPLS-TE (MPLS Traffic Engineering).
For a number of technical issues, which is not the focus of the article, traditional IP routing may have some limitations when defining the best route. Often, by using dynamic criteria for defining the best cost routes, a traditional IP network overloads links while much of the traffic could be routed through underutilized paths.
With MPLS traffic engineering, it is possible to control how data is routed on the network, define protection with rapid convergence to the paths and manage the quality of service and prioritization of flows. (RSVP will be available in DmOS from version 5.6)
Example of an application with MPLS-TE
5. Operation Simplification
The bigger your transport network gets, the more evident the benefits of an IP / MPLS network are. I left one of the main advantages for last, because everything that simplifies your operation has a direct impact on your pocket (OPEX).
After defining all the network infrastructure requirements, that is, configuring all the elements of the topology, the activation of services starts to be done in a much more agile way than in a purely L2 network.
In an L2 network, the activation of services would involve the configuration of all transport network equipment, whereas in an IP / MPLS network there is a need for configurations only in the PEs (Provider Edge) that participate in the service. That is, you will need to configure the service to be activated only at the ends of the link.
Activation of services only in the EP
The number of acronyms and protocols that an IP / MPLS network presents may seem complex, and although you have to consider implementing a new technology at your provider, the benefits will be worth it in the short term.
MPLS will provide your ISP with an optimized and secure way to share the same network infrastructure with its various customers, bringing benefits to both sides. Subscribers will have access to affordable transportation services and the ISP will have a significant reduction in their operational cost (OPEX), in addition to being able to make services more flexible and improve SLAs due to the numerous resources present in the technology.
Datacom has a complete portfolio of switches that implement MPLS, from access paths (EDD) for access, such as DM4370, to equipment with multiple 100GE ports for aggregating and transporting data, such as DM4270. In addition, Datacom has network specialists who can train and assist your team of technicians.
It is worth remembering that Datacom has a complete structure in its headquarters where on-site training is offered. In the training it will be possible to manipulate the equipment, make configurations of different topologies and application scenarios in a complete laboratory environment, in addition to being able to count on the help of our professionals in a series of good practices that will help a lot in the operation of your network.
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