Shulou(Shulou.com)11/24 Report--

Doubt about "A lot of money" Boss Wang runs a company called PTN (Packet Transport Network packet Transmission Network), which mainly uses optical fiber as a medium to provide transmission technologies for various voice and data services. With the advantages of high reliability and flexible expansibility of its product technology, PTN has gradually replaced its counterpart SDH (Synchronous Digital Hierarchy synchronous Digital Architecture) and has a place in the bearer network market. SDH is a company based on TDM (Time Division Multiplexing time Division Multiplexing) technology, which mainly transmits voice services. It's wonderful to host the business battles among companies in the Internet market, but this is another story. Please look forward to it later. Here is a short story about PTN.

One day, Boss Wang took the technical director to see a big client, "a lot of money" lady.

In the negotiation room, Boss Wang explained to Ms. Qian that their PTN technology could perfectly solve network bandwidth bottlenecks and other problems. After that, Boss Wang asked Ms. Qian if she was willing to use their company's products.

Ms. Qian began to look embarrassed: "Boss Wang, I am very interested in your company's products, but I have two questions to ask:"

We established the SDH backbone network in the early years, and there are many users using SDH services. After the newly established PTN backbone network, the cost of maintaining these backbone networks and corresponding access networks will be very high. Can we integrate the access mode of the SDH network with the PTN network without the need for the SDH backbone network?

Our users still have a lot of requirements for TDM services, and they need TDM services to be transmitted between PTN network and SDH network. How to carry TDM services in PTN network? "

02. Lao Li, the technical director of "Li Chenggong", said, "We already have a solution to these two problems. After the completion of the PTN backbone network, traditional networks such as SDH can be moved down to access networks. We perform" pervasion "on all received services and disguise them as what PTN knows. When they are about to leave the PTN network and arrive at users, they will remove the camouflage, so that your problem can be solved perfectly. We call this "cosmetic surgery" PWE3.

After hearing this, Ms. Qian could not help giving a thumbs up: "wonderful ~! I am very interested in your PWE3 technology. I hope this scheme can be landed quickly."

03. "Transfiguration" in the transmission network-- what is PWE3 Transfiguration PWE3? PWE3 (Pseudo-Wire Emulation Edge-to-Edge edge-to-edge pseudo-line simulation) is a two-layer service bearer technology, which imitates the basic behavior and characteristics of ATM, frame Relay, Ethernet, TDM / SDH and other services in PTN network as truly as possible. The core idea of this technology is to establish an end-to-end virtual channel between the service sender and the receiver, in which the transmission of different services is realized. In the process of transmission, it does not care about what business is transmitted, but is only responsible for encapsulation and transmission.

What does PWE3 rely on to change its appearance? Before introducing PWE3 in detail, let's give you a brief introduction to the key elements of PWE3.

CE1, CE2 (Customer Edge): client side edge device, which is used to interface with the edge device of PTN network.

PE1, PE2 (Provider Edge): edge devices on the network side, used for encapsulation and unencapsulation.

AC (Attachment Circuit): access circuit for connecting CE and PE.

VC (Virtual Circuit): virtual circuit for an one-way logical connection between two PE devices.

Tunnels: used to carry PW, providing end-to-end connectivity.

PW (Pseudo Wire): pseudowire, consisting of a pair of reverse virtual links, used to carry customer services. Different customer services are carried by different pseudo-wires.

PW signaling Protocol (PW Signal): creates and maintains PW through parameter negotiation through signaling protocols. LDP (Label Distribution Protocol label Distribution Protocol) is generally used as signaling to transmit VC information.

Inner tag: used to identify PW, containing VC Type, VC ID and other VC information.

Outer tag: used to identify PE2.

How does the business run amok across all networks? What is the business transmission process of PWE3? Combined with the introduction of the components of PWE3 above and the picture below, we can use cross-city express delivery as an analogy. Compare the business to express parcels, CE is equivalent to express stations in the area, PE is equivalent to municipal transit centers, and PW is equivalent to air, water, land and other means of transport.

1. Xiaoming in City A wants to send a parcel to Xiao Hong in City B. Xiaoming calls the courier to collect the parcel.

2. The courier delivers the package to the nearest express site, CE1.

3. The staff of the express delivery station is responsible for loading all the parcels arriving at the station and sending them to PE1, the transit center of A city.

4. After the parcel arrives at the transfer center, the staff affix the inner label to each package, and then distribute it according to the weight, volume, receiving address and delivery service level of the parcel. The parcels with the same attributes are uniformly sealed in a large box dedicated to the express delivery company, and affixed with an outer label.

5. Large parcels are transported to PE2, a municipal transit center in B city, by train, car and other suitable transportation methods.

6. After receiving the large package, the B city express transfer center unpacked the package, tore off the two layers of labels, and distributed it to the express site CE2 in the area according to the express information table in the logistics system.

7. The parcel was delivered by the courier, and Xiao Hong got the package sent by Xiaoming smoothly.

What is the secret to the practice of cosmetic surgery? The secret weapon of PWE3 training is to use PW signaling protocol to establish PW. After the establishment of PW, various services can be transmitted in their own simulated virtual links. Here, taking the mainstream LDP signaling protocol as an example, describes how to use PW signaling protocol to establish and delete PW. Let's use two diagrams to introduce.

Create a pw schematic

1. PE1 sends a Request message and a Mapping (tag Mapping) message (which contains VC tags, VC Type, VC ID, interface parameters, etc.) to PE2.

2. Immediately after receiving the Request message, PE2 sends a Mapping message to PE2 to compare the received Mapping message with the local VC information. If the information is consistent, PE2 accepts the label mapping message, and the one-way VC1 is established successfully. At the same time, PE2 knows the inner tag of PE1.

3. PE1 does the same check after receiving the Mapping message from PE2, and the VC2 is successfully established. At this point, two reverse VC, PW, are established successfully, and PE1 and PE2 notify each other of their status through Notification messages.

Delete pw schematic

When PE1 detects that the status of AC or tunnel is Down, PE1 sends Withdraw and Release messages informing PE2 to remove the label.

When PE2 receives the message, remove the VC1 tag and remove the VC1. Send a Release message to PE1 after the demolition is completed, and the response tag to PE1 has been removed.

After receiving the Release message, PE2 removes the VC2 tag and removes the VC2. At this point, the PW deletion is complete.

04. Summary of the work of "Li Chenggong" the PWE3 makeup program landed smoothly, and PTN Company got a large order from Ms. Qian. Director Li combed and summarized the highlights of this program at the project review meeting.

PWE3 can realize the transmission of different services and the interworking of different networks in some special scenarios. For example, an operator has established a national backbone network, and users have two branches in Shanghai and Beijing. The Beijing branch accesses the backbone network through ATM, and the Shanghai branch accesses the backbone network through FR. Operators only need to establish an PWE3 connection between Beijing and Shanghai to provide users with cross-domain WAN point-to-point services.

The key of PWE3 technology is to establish PW.

PWE3 workflow: encapsulation-transport-unencapsulation.

PWE3 networking mode is divided into single-hop and multi-hop, and its transmission mechanism is the same.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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