Atm Service Types; Cbr; Rt_Vbr; Nrt_Vbr - H3C SR6600 Configuration Manual

ATM Service Types

ATM supports four service types: constant bit rate (CBR), unspecified bit rate (UBR), real-time variable
bit rate (rt_VBR) and non-real-time variable bit rate (nrt_VBR). They are used for the QoS purpose.

CBR

CBR provides ensured, constant bandwidth. The bandwidth assigned to the CBR service is decided by
the peak cell rate (PCR). For a station using the CBR service, ATM cells are sent at PCR continuously
with assured QoS.
Usually, CBR is suitable for jitter-sensitive real-time applications such as audio and video.

rt_VBR

The rt_VBR service is provided for applications that have strict restrictions on delay and jitter, such as
audio and video.
An rt_VBR connection is described by the PCR, sustainable cell rate (SCR) and maximum burst size
(MBS). A station using the rt_VBR service is allowed to send burst traffic at PCR with the maximum
traffic size being MBS without packet loss while the average cell rate being SCR.

nrt_VBR

The nrt_VBR service supports non-real-time applications with burst traffic. An nrt_VBR connection is
described by PCR, SCR and MBS. The nrt_VBR service is suitable for applications that are sensitive to
cell loss but not to delay.

UBR

The UBR service does not make any service quality commitment, guaranteeing neither CLR nor cell
delay. When traffic congestion occurs, cells of the UBR service are always dropped first. The UBR
service is suitable for applications that have low requirements for delay and bandwidth.

Introduction to InARP

On an ATM PVC connection, you can use the Inverse Address Resolution Protocol (InARP) to obtain
the IP address of the remote end connected to the PVC. Thus, you do not need to manually configure
the IP address of the remote end. The following figure shows how InARP works:
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