Resolve MPLS technology: converged routers and ATM switches (1)

Source: Internet
Author: User

During the development of IPOA technology, the classic IPOA (traditional lP on ATM), lane lan simulation), and MPOAATM multi-protocol transmission have gradually emerged) 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.

MPLS network consists of labeled edge router LER) and labeled switched router LSR) 1 ). In LSR, the MPLS control module is IP-centric. The forwarding module is based on the tag switching algorithm and uses the tag Distribution Protocol (LDP) to send Tag Information and Related Signaling between nodes. 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 the packet and establish a specific tag exchange 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.

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.

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