R2511-HP MSR Router Series Interface Configuration Guide(V5)

Configuring ATM and DSL interfaces

ATM and DSL interface

ATM and DSL

Asynchronous Transfer Mode (ATM) is a backbone network technology for transmission of audio, video,

and data. By virtue of its flexibility and support for multimedia services, ATM is regarded as a core

technology for implementing broadband communications.

Digital Subscriber Line (DSL) is a technology providing high-speed data transmission over copper wires.

It includes Asymmetric Digital Subscriber Line (ADSL), High-bit-rate Digital Subscriber Line (HDSL), Very

High-rate Digital Subscriber Line (VDSL), single-pair high-speed DSL defined in ITU-T Standard G.991.2

(G.SHDSL), and Symmetric Digital Subscriber Line (SDSL). These DSL technologies are different in signal

transmission speed and distance and uplink/downlink rate symmetric mode (whether uplink and

downlink rates are the same).

The ATM physical layer lies at the bottom of the ATM reference model. Though it involves specific

transmission media, its functionality does not rely on the transmission mechanism and speed of a specific

medium. Rather, it primarily delivers valid cells and the associated timing signals between the upper

layer and transmission medium. The speeds of physical access media are defined in international

standards such as ATM OC-3c/STM-1, ATM E3/T3, and IMA-E1/T1. Most DSL applications are

ATM-based, combining the advantages of ATM with the low transmission cost feature of DSL. So far, DSL

technologies have been widely adopted for broadband access.

ATM interfaces available on the low-end and mid-range routers

The low-end and mid-range routers provide the following ATM interfaces:

• IMA-E1/T1

• ATM E3/T3

• ATM 25.6 Mbps

• ATM OC-3c/STM-1 based on SONET/SDH

• ATM ADSL based on the ADSL technology

• ATM G.SHDSL based on the G.SHDSL technology

These interfaces support IPoA, IPoEoA, PPPoA, and PPPoEoA. For more information about them, see Layer

2—WAN Configuration Guide.

ATM interface features

The ATM interfaces of low-end and middle-range routers support:

• Nonreal-time variable bit rate (nrt_VBR)

• Real-time variable bit rate (rt_VBR)

• Constant bit rate (CBR)

• Unspecified bit rate (UBR)