Application of MPLS Technology

In the course of the development of IPOA technology, CIPOA (Classic IPOA, that is, traditional lP on ATM), LANE (LAN simulation), and MPOA (Multi-Protocol Transmission on ATM) emerged one after another) IP address switching, CSR (cell Switch Router technology), ARIS (Integrated IP address switching technology), TapSwitching (Label Switching Technology), MPLS and other technologies. These IPOA technologies can be divided into two types: overlapping models and integration models.

The integration mode uses MPLS technology as a solution. MPLS is a new network standard, which has been widely recognized. The starting point of this technology is to integrate routers and ATM switches to improve the transmission speed of IP packets, simplify the network, and serve as an international standard for L3Switching (layer-3 Switching) technology.

The MPLS network consists of the labeled edge router (LER) and the labeled exchange router (LSR) (1 ). In LSR, the MPLS control module is IP-centric. The forwarding module is based on the tag switching algorithm and sends Tag Information and Related Signaling between nodes through the tag Distribution Protocol (LDP. LDP signaling and tag binding information are transmitted only between neighboring MPLS nodes. Standard routing protocols need to be run between LSR or between LSR and LER to obtain topology information. With this information, LSR can clearly select the next hop of a message and establish a specific tag switching path (LSP ). MPLS uses the control drive model, that is, it initializes the allocation and forwarding of tag binding information used for creating LSP Based on the topology drive mode. The LSP is a one-way transmission path. Therefore, two LSPs are required for the full-duplex service, and each LSP is responsible for the business in one direction.

Figure 1 MPLS network diagram

The following four steps can be taken to transfer data in an MPLS network.

Step 1: The network can automatically generate a route table because the vro or ATM switch can be used in internal gateway protocols such as OSPF/ISIS information exchange. LDP uses the information in the route table to establish the tag value of adjacent devices. This standard creates LSP and sets the correspondence with the final destination in advance, unlike the permanent virtual circuit of ATM, you need to manually set VPI/VCI. MPLS labels are automatically assigned.

Step 2: when a data packet enters the edge LER, it will be processed to determine which layer-3 services are needed, such as QoS and bandwidth management. Based on the routing and policy requirements, edge LER selectively adds a tag to the data packet header and then forwards it.

Step 3: The LSR at the core of the network reads the mark of each packet and replaces a new one based on the switch table. This action will be repeated among all the center devices.

Step 4: remove the tag and read the data packet header from the LER at the egress edge and forward it to the final destination.

MPLS integrates IP routing and ATM switching technology to realize router intelligence and use the efficient hardware exchange of ATM switches. The perfect combination of ATM and IP can be better than any other technology.

MPLS technology can improve the forwarding capability of routers, thus improving the performance of the entire IP network. In addition, you only need to upgrade the software on your existing vro to fully support the MPLS technology, this ensures your original investment.

The MPLS solution provides intelligent IP Application Services for the ATM network, which is different from the ATM/FR transmission service. Compared with the IP-OVER-ATM solution, IP data streams and ATM data streams are processed in the same way, which limits the ability to implement end-to-end IP services. MPLS enables service providers to maintain the current turnover of ATM and FR services by using IP and ATM properties. In addition, commercial IP services such as Internet and ExtranetVPN are provided on the same network to increase the output value and profit.

MPLS is only a technology of Multi-Service ATM networks. network operators can still provide existing FR, voice, and Multi-Service ATM Transmission Services. Through the IP + ATM platform, a variety of network services such as IP, FR, and ATM can be supported through a single network using the Virtual Switching port (VSI) technology. VSI is a new standard for Multi-Service Forum (MSF). It is used to separate layer-2 switching and layer-3 Control for fast mode design, improving the flexibility and scalability of switches. VSI allows you to explicitly control the network resources allocated to each service. Therefore, each virtual network is independent of each other. VSI supports both MPLS, PNNI, and other control platforms because it allows different protocol stacks to run simultaneously on the same IP + ATM switch.

Without MPLS, IP address transmission through ATM requires a complex protocol translation process. The IP address routing corresponds to the ATM address and route, and is placed in the ATM exchange table. In this case, the ATM network requires the PNNI routing protocol and the ATM Address Resolution Protocol (ATMARP) to map the IP network segment to the ATM network segment, and then implement inter-network routing through NHRP. On the contrary, MPLS omits the complexity of ing IP addresses and routes to an ATM switch table. MPLS tag switching is the same as that of an ATM switch.

Through MPLS, IP unicast, and multicast information integration with the existing ATM system, service providers can not only provide IP services to users, but also bring benefits to the growing Internet: by ing the IP priority level with the queues of different service levels in the ATM switch, the end-to-end QoS is provided for users. The bandwidth allocation of each MPLS priority can be adjusted as needed; you can use the Bandwidth Reservation and allocation functions of Opticlass to meet different bandwidth, priority, and latency requirements.

In addition, the TrafficEngineering function enables service providers to allocate and adjust bandwidth and provide value-added services such as VPN (Virtual Private Network) as required by Traffic. The rich and powerful functions of MPLS allow service providers to build their own large and scalable business service networks, while at the same time being more competitive in the market.

MPLS has high scalability. The combination of traditional IP addresses and ATM relies on the translation of intermediate layers. This method has brought about a series of consequences, such as the "N square" problem of virtual circuits. MPLS effectively solves these problems and improves the scalability of ATM.

MPLS mainly solves the scalability problems caused by the combination of IP and ATM in the following ways:

VC merge: to reduce the number of virtual circuits and reduce system overhead, A VCMerge technology is adopted. It can compress multiple virtual circuits into a group and use a tag together. In this way, the virtual circuit is equivalent to a virtual circuit.

Supports CIDR: Both EdgeLSR and LabelSwitchingController support standard IP routing protocols, such as BGP4 on the INTERNET backbone network and the internal routing protocols adopted by most telecom carriers, standard IP Routing protocols such as OSPF and IS-IS support CIDR (Classless Inter-Domain Routing) defined in RFC1519 ).

The main function of CIDR is to reduce the total number of class c cidr blocks in the routing table. Therefore, in today's international Internet backbone network, there are only 600,000 CIDR blocks, not 2,000,000 CIDR blocks. Because of the decrease in the total number of Route tables, the query speed of the router is greatly improved, and the Memory and CPU requirements of the router are also reduced. This function is completed by the flag router. Because of the CIDR function, the total number of LVC instances required for the flag switch is greatly reduced.

Support for IPCoS (ClassofService): MPLS provides interworking with the Class of Service (IP CoS), enabling telecom operators to provide CoS of different levels to the general public with higher scalability, communication with RSVP is provided, or specific QoS is provided through Traffic Engineering. Therefore, the total number of TVC instances is also reduced to a considerable extent.

Avoid end-to-end Rerouting (Rerouting): Each switch has layer-3 intelligence and can be re-selected for connection. Therefore, even if the backbone network fails, the service will not be interrupted. When a route in the middle fails, the system does not re-build the chain as it used to (this takes a long time), but uses a roundabout method of re-selecting the path. This not only improves connectivity, but also minimizes system overhead. In the traditional IP technology, the IP address space is very large, and indexing and searching cannot achieve hardware. This will greatly reduce the network speed. However, the advantage of ATM is that, after marking and virtual circuits are used, tags are used for indexing to avoid long searches in the route table. Therefore, it allows IP addresses to directly drive hardware and achieve ultra-high-speed query indexes. In this way, no cell-based processing is required. Therefore, cell buffers in large routers are saved, saving costs.

In addition, MPLS also supports IPVPN services, which will be the Business Growth Point of telecom operators.

For the newly added IP business service, the most significant benefit of MPLS is the ability to allocate tags, which has a special significance. Different tags can distinguish routing information, application type, and service level. The MPLS flag is similar to the pre-calculated switch table in the central device and contains the layer-3 Information. Each switch is allowed to automatically assign each packet to the correct IP service. The table is pre-calculated, therefore, there is no need to reprocess data packets at each hop. This not only makes data traffic classification possible, for example, separating the best-effort data stream from the data stream based on important tasks, but also provides high scalability.

MPLS reduces the time required for data forwarding and Analysis of IP headers, because it uses the tag switching mechanism, marking is only limited by local limitations, so there is almost no possibility of using up the tag, this feature is the basis for implementing value-added IP services, such as QoS and VPNTracfficEngineering.

To sum up, MPLS integrates the advantages of IP and ATM technologies, uses a layer-3 routing mechanism combined with LDP to establish route tables and forward tables, and uses layer-2 ATM technology for fast exchange, it provides a superior technical foundation for a new generation of telecom networks. It can achieve three layers of flexibility and scalability, as well as two layers of fast switching, traffic management, security, and QoS assurance mechanisms. MPLS has proved to be the best solution for large-scale network scalability.