Alstom DS Agile H38 Series, Инструкция по установке и эксплуатации

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H38x/EN GL/D11 Global Documentation
Page 14/53 DS Agile H38x
The figure below shows an example of a PRP network. The doubly attached nodes DANP 1
and DANP 2 have full node redundancy, while the singly attached nodes SAN 1 and SAN 4
do not have any redundancy. Singly attached nodes can, however, be connected to both
LANs, via a device that converts a singly attached node into a doubly attached node. This
product does that. A device that performs this function can be referred to as a RedBox (a
contraction of redundancy box).
Devices with single network cards such as personal computers, printers, etc., are singly
attached nodes (SAN) that may be connected into the PRP network via a RedBox as shown
in the figure below. This is the case for SAN2 and SAN3. Because these SANs connect to
both LANs, they can be considered as Virtual Doubly Attached Nodes and described as
VDANs.
LAN A Switch LAN B Switch
DANP 2 RedBox DANP 1
SAN 1 SAN 4 SAN 2 SAN 3
S1031ENa
FIGURE 2: EXAMPLE PRP REDUNDANT NETWORK
To achieve high-availability configuration the first interface is connected to LAN A and the
second to LAN B. The topologies of LAN A and LAN B are open and the networks could be
applying other redundancy approaches. A DANP transmits its packets on both interfaces and
hence over both networks. In an error-free environment a second DANP receives the same
packets on both interfaces, possibly with a time delay between them. The receiving DANP
will use the first of these packets, ignoring the second. PRP networks do not need
reconfiguration nor path switching.
The two LANs are identical in protocol at the Media Access Control (MAC) level, but they
can differ in performance and topology. Transmission delays may also be different. The
LANs have no direct connection between them and they are assumed to be fail-independent.
3.2 Base-Tx Ethernet Switch function
The Base-Tx Ethernet Switch function manages three Ethernet ports presented for user
connection using RJ45 connectors. These are qualified by LED indications of link activity.
If a cable is not connected to a port, most of the circuitry for that port is disabled to save
power.
Using auto-negotiation, the product automatically determines the speed of transmission on
the 10/100 Base-Tx ports according to the IEEE 802.3u standard. It also determines
whether communication is half-duplex or full-duplex, and adapts accordingly.
Each Ethernet device inserts its unique “MAC address” into each message it sends. The
receiving port automatically recognises the MAC address in a received frame and stores it.
Once an address is recognised and stored, the switch will forward frames to the appropriate
port. Up to 1024 MAC addresses can be stored and monitored at any time.