Mobile Tutorials, Satellite And IPTV tutorials, PC And Automotive Tips

What Exactly is a Broadband Remote Access Server (BRAS)?

Home » Technology » What Exactly is a Broadband Remote Access Server (BRAS)?

Published on at > Last Updated by .- Leave a Comment

English students might find the term ‘BRAS’ confusing, as it sounds like ‘bras’ (a type of female underwear). However, today’s article isn’t about underwear. Instead, we are discussing a different BRAS: the Broadband Remote Access Server, also known as the Broadband Access Server. This article will provide an in-depth understanding of what BRAS is.

 

Understanding Broadband Remote Access Server

 

 

As the name suggests, BRAS is related to our broadband Internet access services. Without it, our home broadband would not work properly, and we would not be able to surf the Internet.

Understanding Broadband Remote Access Server (BRAS)?

Before introducing BRAS in detail, let us first lay some foundation. What is a transmission network? The transmission network is the foundation of our entire communication network and connects home users, government and enterprise users, and data centers worldwide. It is also the backbone of the Internet.

The transmission network consists of the backbone/core and metropolitan area networks.  As the name suggests, a metropolitan area network is a communication network within a single city (abbreviated as MAN, Metropolitan Area Network).

The metropolitan area network is subdivided into three layers: core, aggregation, and access. Most people now use fiber optic Internet access, and every household has an optical modem.

The scientific name of “optical modem” is ONT, which belongs to the PON (Passive Optical Network) system. The PON system is part of the metropolitan area network’s access layer.

Simply put, PON transforms one optical fiber into N optical fibers, thus realizing “optical connection” for thousands of households. You may think of routers. Routers also have the function of distribution and aggregation, turning one network cable into N network cables.
|

So, is PON a “fiber-optic version ” of a router?

The precise answer is no.
PON (Passive Optical Network) is the underlying system that manages and delivers the optical fiber connection to your home. In other words, it’s like connecting a water pipe to your home without water flowing through it. PON provides the infrastructure, but an active service provider needs to supply the data (like water).

So, we need BRAS .
If you have tinkered with wireless routers or optical modems, you must be familiar with the following interface:

PPPOE dial-up interface

After entering your username and password and clicking ‘Dial,’ you can access the Internet if the connection is successful. This PPPoE dial-up process is like providing your broadband account information to the operator and requesting they ‘turn on the water pipe’ to deliver service to your home.

This is a typical authentication process, and authentication is one of the main functions of a BRAS. Simply put, operators cannot identify users, determine user permissions, or manage billing without a BRAS.

Where is the Broadband Remote Access Server’s position in All Of This?

BRAS is the core router CR of the backbone network
CR: Core Router, SR: Service Router. SW： Switch
As shown in the figure above, BRAS is generally deployed at the core layer of the metropolitan area network. As can be seen from the network diagram, BRAS is the bridge between the access network and the backbone network. It is a gateway that controls the user’s data in and out of the backbone network. In other words, it is like a toll station on a highway, managing and charging users.

Understanding Broadband Remote Access Server

In addition, the backbone network’s core router (CR) serves as the entry and exit point for all metropolitan area network traffic.For a user to access the Internet, the optical path of the PON must first be functioning properly. Then, a PPP (Point-to-Point Protocol) session is established between the optical modem (which can also be a wireless router) and the BRAS. PPP is a data link layer protocol. Once the PPP session is established, users can access the Internet via the backbone network.

The PPPoE we mentioned earlier is PPP over Ethernet (there was also PPPoA, which is PPP over ATM in the past).
The process of establishing a PPP session is shown in the figure below. These are all protocol flows, so I will not introduce them in detail. You can check the relevant information.

BRAS and PPP session

 

BRAS completes authentication and billing functions by cooperating with the authentication and billing systems. It is worth mentioning that another important network element, the RADIUS server (Remote Authentication Dial-In User Service), is needed to complete the authentication. In the above figure, after the BRAS receives the username and password from the terminal side, it will look for RADIUS authentication.

In addition to authentication, authorization, and billing, BRAS can also be used for QoS, security management, multicast, and VPN.
 As the control center of the broadband network, it is the core network of the broadband network. It is combined with the operator’s operation support platform and can also carry out many imaginative value-added services, making it a veritable “big housekeeper.”

Development and Evolution of BRAS

BRAS (Broadband Remote Access Server) was introduced during the ADSL era when broadband users surged dramatically. It streamlined network architecture and enabled centralized management, laying the groundwork for broadband services’ rapid expansion.

Later, BRAS expanded its support beyond xDSL to include Cable Modems, Ethernet access (LAN), wireless broadband data access (WLAN), FTTx (fiber optics to buildings and homes), and other network types. It supports data access for broadband IP and ATM networks, becoming a preferred choice for operators, government, and enterprise customers.

Around 2017, BRAS Began a New Evolution.

I mentioned earlier that BRAS is like the mobile network’s core network. More than ten years ago, the core network had an obvious evolution. The separation of control and forwarding. In other words, the equipment is decoupled, and the control plane and data forwarding plane are separated, each taking its path. 
Traditional BRAS, as a gateway, is responsible for both user management and data flow forwarding. The burden is heavy, and it isn’t easy to improve performance.

Moreover, there are a large number of BRAS devices. As the network scale continues to expand and new services are launched, the maintenance workload of BRAS is increasing. The speed of deploying new services is also prolonged, affecting the network’s long-term development.

Therefore, BRAS began to decouple, extract, and centralize the user management functions on multiple BRAS devices to form the control plane (CP). On the BRAS device, the control plane of the router and the forwarding plane of the BRAS were retained to form the forwarding plane (User Plane, UP).

Like the mobile core network, virtualization (cloudification) forms vBRAS and centralizes the control plane. The benefits are the same as those of the cloud core network, which can flexibly expand and shrink capacity, simplify operation and maintenance, unify standard interfaces, and improve equipment performance.

In addition to using vBRAS, the forwarding plane has also become flexible.

High-traffic services, high-performance hardware, and distributed deployment can be used to meet forwarding performance requirements. For large-session and low-traffic services, x86 cloud devices can be used for centralized deployment to save costs.

The emergence of vBRAS reflects the cloudification trend of metropolitan area networks. Its underlying evolution logic is the same as that of 4G/5G mobile communication networks.

It is worth mentioning that the positioning of BRAS has also changed in addition to the morphological changes.

As equipment performance improves, the BRAS and SR (service router) that we saw earlier are gradually integrated into MSE (Multi-Service Edge) or BNG (Broadband Network Gateway). This is also a form of integration.

Well, that’s all about BRAS. BRAS is crucial for fiber broadband services. If it is not working, we cannot access the Internet and enjoy a smooth network experience.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.