System information

8 Special Implementations
The physical layer is part of the OSI model which is an abstract description for network
protocol design. Normally, the bus interface has a higher throughput as the physical link
interface. Therefore, FIFOs are used to optimize the data traffic. The CHARM provides
an additional network interface to the host computer. This interface is used to establish
a network connection between the CHARM and the host computer without using a net-
work cable. The CHARM obtains additional information about the host computer via this
network connection the operating state or the CPU utilization of the host. Next section
illustrates the CHARM-Host network bridge. Additionally, the CHARM provides a fallback
network interface for the host computer. In case the network of the host computer fails, the
CHARM can provide a network route to the host computer. This approach is discussed at
the end of this chapter.
8.2.1 CHARM-Host Network Bridge
In principle, there is no internal network connection between the CHARM card and the
host computer. However, the CHARM card can access to the host computer by the aid of
the network interface of the CHARM card and the one of the host computer. Therefore, a
network route between the host and the CHARM card is required. It can be established,
for example, by using the same network switch.
Picture 8.5 illustrates a possible network connection from the CHARM to the host com-
puter. A direct network connection via the Ethernet interface from the CHARM card to
the host would not be appropriate. In the case of a direct Ethernet connection, you would
not be able to access the CHARM if the host computer fails.
CHARM Host
CHN
NIC
Intranet /
Internet
PCI
TCP/IP
TCP/IP
192.168.0.5
192.168.0.4
10.0.1.7
10.0.1.11
Management
Computer
NIC
Figure 8.5: CHARM-Host network communication. In principle, there is no direct network
connection between the host and the CHARM. But the PCI bus is used to
establish a network bridge between the CHARM and the host computer.
A framework was developed which enables a generic network interface from the CHARM
card to the host computer without using the Ethernet network interface [3]. In this case,
the PCI bus is the data link layer and the physical layer.
Figure 8.6 shows a block diagram of the implemented network function. The left part
of the picture shows the local system of the CHARM which is connected to the FPGA
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