MPLS - what is it?

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MPLS - what is it?
MPLS - what is it?

In modern enterprises, when building the infrastructure of a corporate network, MPLS technology can be used. What are its features? What advantages does it have over traditional routing technologies?

MPLS what is it
MPLS what is it

Technology overview

What is the specificity of MPLS? What is this technology? MPLS is a concept in which computer networks perform packet forwarding. Its main feature is that it offers an alternative to IPLP-type routers analyzing headers for all packets, which is carried out in order to determine the direction for forwarding them to the next infrastructure component. If the technology under consideration is used, then the analysis of the header is carried out once when entering the MPLS network, and then a check of the correspondence between the packet parameters and the properties of the stream is initiated.

MPLS development features

MPLS was developed by professionals interested in implementing a universal data exchange protocol that would be suitable for both circuit-switched infrastructure and packet-based applications. In MPLS networks, a variety of types of traffic can be transmitted -IP, ATM, Ethernet, SONET, SDH. The development of the concept was carried out taking into account the advantages and disadvantages of earlier protocols of a similar purpose. At the same time, in some aspects, MPLS involves the implementation of simpler algorithms in comparison with the approaches used in traditional solutions. According to experts, network equipment that supports MPLS technology is able to displace traditional solutions from the market, which indicates that the MPLS developers have done a good job of optimizing and universalizing this concept.

MPLS network
MPLS network


So, we know the basic principles of the MPLS concept, what kind of technology it is. In conventional networks that use the TCP-IP protocol, packet routing is implemented using the IP address of the computer to which the packet is sent. In the network, all routers have information about which interface is used for data transfer, as well as about which computer the current packet needs to be redirected to.

In the case of using MPLS, a different approach is taken. It, as we already know, involves the implementation of switching using labels. They are tied to a specific packet that is transmitted on the network. Routers, having received it, simultaneously have information about how to transfer data further - based on the specific value that the MPLS label has. It can be noted that it is located within the MPLS header placed between the frame and the packet, in accordance with the accepted format. It is noteworthy that on oneA package can contain multiple labels. In order to indicate that this or that label is the last one in the group, special flags are used.

It will be useful to consider in more detail the advantages of the technology in question over traditional solutions.

MPLS Mikrotik
MPLS Mikrotik

Key Benefits of MPLS: Efficiency of Data Processing

The biggest advantage of MPLS is that it takes less time to process data than IP address matching. Moreover, MPLS technology reduces the time it takes to forward a packet using core routers. In fact, switching can be carried out using several protocols, in which special labels are used within the packets of transmitted network data. Due to this, separate switched flows are formed.

MPLS benefits: versatility

Another important property of the concept is versatility. Virtually any network IP MPLS can be implemented. The technology under consideration is well supported at the hardware level. In principle, it is possible to use affordable solutions for the implementation of MPLS - Mikrotik, for example. The principles of bringing infrastructure into working condition are universal. However, when designing an MPLS network, the configuration of the equipment must be done by experienced professionals. First of all - competent in understanding the features of the network architecture, the characteristics of its hardware components.

MPLS label
MPLS label

MPLS Advantages:scalability

MPLS infrastructure is characterized by scalability and a high degree of autonomy in relation to the various protocols through which data is transmitted. The specifics of specific standards implemented at the data link layer do not matter. When implementing an MPLS network, there is no need to ensure the functioning of networks at the second level, which are optimized for the transmission of certain types of traffic. From the point of view of network classification by the type of switching, MPLS can be legitimately attributed to the infrastructure in which packet switching is carried out.

MPLS architecture: basic devices

Let's study what devices are supposed to be used in networks where the MPLS concept is used, what kind of infrastructure it is in terms of using hardware resources. The main devices that are used within the framework of the relevant technology can be called:

- a router compatible with the MPLS concept, as well as with conventional data transfer protocols;

- a router that interacts with devices on which label switching is not performed (including due to the lack of MPLS support);

- a group of network devices that are used for label switching within the overall administration and routing system.

In fact, devices of the first type form a corresponding group, which, in turn, forms a domain. MPLS routers of the second type form the border area of this domain.

MPLS routers
MPLS routers

Basic Principles of MPLS Switching

Let's study on the basis of what principles switching is carried out within the framework of the technology in question. As we already know, the key component of MPLS is the label. Their exchange is the basis of the corresponding technology. All packets that are transmitted on the network are associated with a certain type of network layer. Each of them is identified with a specific label. Its value is unique only when considered within a specific section of the path that runs between network nodes located in the neighborhood, that is, routers of the first type (according to the classification discussed above). Any packet will thus include the label. However, how it is associated with a packet will depend on the technology used within the network link infrastructure.

IP MPLS networks
IP MPLS networks

Communication between routers

A particular router can query the network using some MPLS-compliant algorithm - BGP, for example. The main function of the device in this case is to provide data exchange with neighboring devices through the distribution of labels, which are subsequently used for switching purposes. Direct exchange of them can be carried out in different ways. For example, the LDP protocol may be involved, or modified versions of other routing standards used by the network administrator.

Component table

In the process of label distribution, when different devices communicate, separate transmission paths are formeddata. Each of the routers used uses a table that matches the components associated with the ingress interface and the sections that reflect the characteristics of the egress infrastructure. The router, having received this or that packet in accordance with the interface number, and also after reading the value of the label, sets a specific output interface for the transmitted data. In this case, the previous value within the label is corrected and replaced by a new one, which is reflected in the part of the table where the output labels are fixed, after which the packet is sent to another element of the network infrastructure.

MPLS setting
MPLS setting

The MPLS protocol assumes a one-time identification of individual field values located in one row of the table used. This is the reason for the fact that the concept under consideration allows for faster data transfer compared to the methods used in conventional routing, when the IP address of the source device has the longest prefix within the routing table.

MPLS structure

Let's consider in more detail the features of the structure of the network concept in question. MPLS has two main components:

- kernels;

- border area.

There are devices in the kernel structure that must support MPLS. They are used as infrastructure components for routing traffic within a switched protocol. Thus, the main function of the devices present in the kernel is switching.

In turn, the boundary area is responsible for classifying packets according to established criteria, for implementing related services - for example, those related to filtering during data transmission, for managing network traffic. The specified distribution of functions between the core and the border area allows you to configure the MPLS network, taking into account the specifics of the location of specific devices within the network.

Methods of marking packages

Let's study in more detail how data transmission packets are marked using MPLS-tags. First of all, it is worth noting that the label has the following main characteristics: fixed length, uniqueness in the context of a single connection that is made between neighboring routers.

In fact, a label with the same value can be used in different parts of the network, but only within the framework of communication between separate pairs of routers. True, in this case, the devices must determine where exactly the data packet came from, labeled with the appropriate label. In practice, the simplest network connections can use the same set of MPLS labels within an interface.

In more complex infrastructures, a separate set of labels is expected to be used within a separate module or device. Immediately before being included in the packet, the MPLS label is encoded in accordance with the established algorithm. If the network uses the IP protocol, then the label is placed within the packet header. In other cases, it is reflected in the header of the protocol.already at the channel level. It can also be encoded in a specific value.

Apply label groups

In the process of data transmission using the considered network concept, the packet structure may contain, as we noted above, groups of labels - stacks. Each of them can reflect the operation of adding or removing certain labels. In this case, only in the topmost one a specific switching result is specified. This feature of data transmission in MPLS networks makes it possible to implement tunnel communications. The stack contains components that are 32 bits long. In this case, 20 is assigned to the label, 8 - to the packet lifetime counter, 1 - reflects the lower limit in the label group, 3 - are not used in practice. In general, any label value is possible - except for a number of reserved ones.

Switch path structure

To understand in detail the principles of the MPLS network, what kind of technology it is, it will be useful to study the features of the structure of the switched path, which is built within the network infrastructure. Its main feature is that it consists of a set of sections - on the same level. On them, switching is carried out using labels for a specific level.

The structure of one or another level assumes the use of input and output routers. We noted above that the LDP protocol can be used in MPLS networks. Let's explore how a switched path can be built when LDP is enabled.

The first step in the distribution of UDP packets, in whicha large number of addresses can be involved, routers establish their own location on the network - using LDP. Links can also be defined between routers that are not on the same link. This feature of the network structure is important from the point of view of implementing data transmission in the tunnel format.

After the location of the routers is established, the LDP protocol starts the connection outside of TCP, that is, on top of it. Within it, requests are generated to initiate the binding, as well as information about it. Test messages can also be sent between different devices to verify that the network is working.

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