System information

FCD 901 48
Issue R2A, 07.2009
XMP1 Release 5.5 System Description
Ethernet Functions
Page 4-4 Proprietary Information Aastra
4.3 Ethernet Functions
The Ethernet expansion of the XMP1 system supports the following
functions:
• EPL (Ethernet Privat Line)
• Transparent transmission via SDH (VC-12, VC-3)
• Data rates up to the maximum velocity of the Ethernet interface
• Virtual Channel Concatenation (VCAT)
• GFP-F Framing Procedure
• Link Capacity Adjustment Scheme (LCAS)
• Link Loss Forwarding (LLF)
• Pause
• Auto-Negotiation
• Auto-MDIX
Ethernet Private Line (EPL)
Ethernet traffic signals are transported via the SDH network over an
Ethernet Private Line (EPL). In its simplest form, this can be a simple
point-to-point connection between two physical Ethernet interfaces.
Although an Ethernet interface is assigned a certain bandwidth (10Mbit/s,
100Mbit/s) on a permanent basis, the traffic volume to be transported via
the corresponding port is much smaller most of the time. In contrast to PDH
systems, the signals are not permanently assigned to a certain VC type at
the physical interface. Instead the Ethernet traffic is typically transported in
a group of concatenated VCs via the SDH network, the number of VCs and
VC types being sufficient for transmitting the Ethernet traffic bandwidth
agreed.
Generic Framing Procedure (GFP)
The Generic Framing Procedure (GFP) provides an 'Encapsulation'
mechanism for Ethernet MAC frames in compliance with IEEE 802.3 and
their transmission via an SDH carrier.
LCAS
The Link Capacity Adjustment Scheme (LCAS) controls the link capacity
using virtual concatenation. The capacity is reduced automatically as soon
as one or several VCs in the group detect an error in the network. The
capacity is in turn increased again automatically as soon as this error is
eliminated. The LCAS procedure permits an error-free and hitless addition
and deletion of VCs in a concatenated group.
Link Loss Forwarding (LLF)
Link Loss Forwarding is a mechanism with alternative routing processes
offering protection in the data equipment connected.
Pauses
In Ethernet transmission, pause frames provide a so-called flow-control
mechanism slowing down the Aggregate transmission rate of the frames
sent by the far end.