Overview of ipoa, ipoeoa, and eoa, Ipoa, Ipoeoa – H3C Technologies H3C SR8800 User Manual
Page 11: Atm service types, Rt_vbr
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Overview of IPoA, IPoEoA, and EoA
, and
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IPoA
IP over ATM (IPoA) enables ATM to carry IP packets. In an IPoA implementation, ATM serves as the data
link layer protocol for the IP hosts on the same network. To enable these hosts to communicate across an
ATM network, IP packets must be encapsulated in ATM cells.
By making full use of the advantages of ATM, IPoA delivers excellent network performance and
ubiquitous mature QoS assurance.
IPoEoA
IPoE over ATM (IPoEoA) adopts a three-layer architecture, with IP at the uppermost layer, IP over Ethernet
(IPoE) in the middle, and IPoEoA at the bottom.
IPoEoA is suitable where Ethernet packets are to be forwarded through ATM interfaces. A typical
application of IPoEoA is using ATM PVCs to connect your router to a remote access server over a long
distance for high-speed access to the Internet. In this application, you must configure IPoEoA on the
connecting ATM interfaces.
As for IPoEoA, you can associate multiple PVCs with one virtual Ethernet (VE) interface. PVCs associated
with the same VE interface can communicate at Layer 2.
EoA
Ethernet over ATM (EoA) adopts a two-layer architecture, with Ethernet at the upper layer and EoA at the
lower layer. It requires that Ethernet packets be forwarded through ATM interfaces.
With EoA, a router can implement Layer 2 unicast, broadcast, and multicast.
You can associate only one PVC with one virtual Ethernet bridge (VE-bridge) interface (also referred to as
a Layer 2 VE interface).
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 and 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.
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