Broadband Remote Access Server
Encyclopedia
A broadband remote access server (BRAS, B-RAS or BBRAS) routes traffic to and from broadband remote access devices such as digital subscriber line access multiplexer
s (DSLAM) on an Internet service provider
's (ISP) network.
The BRAS sits at the core of an ISP's network, and aggregates user sessions from the access network
. It is at the BRAS that an ISP can inject policy management and IP Quality of Service
(QoS).
The specific tasks include:
A DSLAM
collects data traffic from multiple subscribers into a centralized point so that it can be transported to a switch or router over a Frame Relay, ATM, or Ethernet connection.
The router provides the logical network termination. Common link access methods include PPP over Ethernet (PPPoE), PPP over ATM (PPPoA) encapsulated sessions, bridged ethernet over ATM or Frame Relay (RFC 1483/RFC 1490), or just plain ethernet. In the case of ATM or Frame Relay based access, individual subscribers are identified by Virtual Circuit IDs. Subscribers connected over ethernet-based remote access devices are usually identified by VLAN IDs or MPLS tags. By acting as the network termination point, the BRAS is responsible for assigning network parameters such as IP addresses to the clients. The BRAS is also the first IP hop from the client to the Internet.
The BRAS is also the interface to authentication, authorization and accounting systems (see RADIUS
).
Digital subscriber line access multiplexer
A digital subscriber line access multiplexer is a network device, located in the telephone exchanges of the telecommunications operators. It connects multiple customer digital subscriber line interfaces to a high-speed digital communications channel using multiplexing techniques...
s (DSLAM) on an Internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
's (ISP) network.
The BRAS sits at the core of an ISP's network, and aggregates user sessions from the access network
Access network
An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...
. It is at the BRAS that an ISP can inject policy management and IP Quality of Service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS).
The specific tasks include:
- Aggregates the circuits from one or more link access devices such as DSLAMDigital subscriber line access multiplexerA digital subscriber line access multiplexer is a network device, located in the telephone exchanges of the telecommunications operators. It connects multiple customer digital subscriber line interfaces to a high-speed digital communications channel using multiplexing techniques...
s - Provides layer 2 connectivity through either transparent bridging or PPPPoint-to-Point ProtocolIn networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
sessions over EthernetEthernetEthernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
or ATMAsynchronous Transfer ModeAsynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
sessions - Enforces quality of service (QoS) policies
- Provides layer 3 connectivity and routes IP traffic through an Internet service providerInternet service providerAn Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
’s backbone network to the Internet
A DSLAM
Digital subscriber line access multiplexer
A digital subscriber line access multiplexer is a network device, located in the telephone exchanges of the telecommunications operators. It connects multiple customer digital subscriber line interfaces to a high-speed digital communications channel using multiplexing techniques...
collects data traffic from multiple subscribers into a centralized point so that it can be transported to a switch or router over a Frame Relay, ATM, or Ethernet connection.
The router provides the logical network termination. Common link access methods include PPP over Ethernet (PPPoE), PPP over ATM (PPPoA) encapsulated sessions, bridged ethernet over ATM or Frame Relay (RFC 1483/RFC 1490), or just plain ethernet. In the case of ATM or Frame Relay based access, individual subscribers are identified by Virtual Circuit IDs. Subscribers connected over ethernet-based remote access devices are usually identified by VLAN IDs or MPLS tags. By acting as the network termination point, the BRAS is responsible for assigning network parameters such as IP addresses to the clients. The BRAS is also the first IP hop from the client to the Internet.
The BRAS is also the interface to authentication, authorization and accounting systems (see RADIUS
RADIUS
Remote Authentication Dial In User Service is a networking protocol that provides centralized Authentication, Authorization, and Accounting management for computers to connect and use a network service...
).