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ASSA ABLOY Hospitality
66 1100 005-11
above, but this time requests the IP address offered by the
DHCP server.
9. The DHCP server sends a
DHCP ACK packet
, confirming that the Ethernet
module may start using the new IP address. Unlike the ACK in
this ACK packet must be sent to IP destination address 255.255.255.255
(
IP broadcast
), since the Ethernet module has not got any confirmed
IP address yet.
10.The Ethernet module performs gratuitous ARP (
Address Resolution Protocol
)
to ensure that no other host has got the same IP.
11.If IP collision is detected, the Ethernet module sends a
DHCP Decline packet
which refuses the assigned IP address and restarts the IP acquirement
procedure for the Ethernet module.
12. If there is no DHCP server available on the subnet, the Ethernet module
self-assigns an IP address from the IPv4 Local Link address space
(169.254.0.0/16), and sends gratuitous ARP to ensure that no
other host has got the same IP.
13. The Ethernet module reads the most recently used Visionline server
IP address and tries to open a TCP connection to the server.
14. If the TCP connection attempt fails, the Ethernet module will continue
to try connections to the same IP over and over again – unless it detects
that the network/subnet setup has changed, e.g. the Ethernet module may
have been moved to a new location. Then it will send an application specific
service discovery request (
announcement broadcast
) with IP destination
address 255.255.255.255;
IP broadcast
. Even if the network/subnet setup is
unchanged, but long time (one hour) has elapsed without any successful TCP
connection with the Visionline server, the Ethernet module will start sending
service discovery requests.
15. If a Visionline server is on the same subnet - or if another Ethernet module
with a valid TCP connection to the server is on the subnet - it will send a reply
to the querying unit, letting it know the IP address and TCP port of the
Visionline server. The Ethernet module then tries TCP connection to that IP.
From the payload supplied in the reply (the reply is sent with IP destination
address 255.255.255.255,
IP broadcast
), the querying unit can determine if
its own IP address properties are correct with respect to network class, default
encoder IP and subnet mask. If required, it will self-assign a new IP address
within the subnet specified in the reply, and then send gratuitous ARP to
ensure that no other host has got the same IP. Then it goes on and tries
TCP connection to the received server IP address.
16. Prior to sending the service discovery request, the Ethernet module tries
to contact a DNS server (d
omain name system
), with a request for resolving
the most recently used
Server Host Name
. If that name is unknown to the
DNS, the encoder tries to resolve the factory default Server Host Name.
If any of the two names renders a successful DNS reply, the encoder uses
the IP address received from the DNS server, and tries TCP connections to that
address. If the factory default name is unknown too, or if a DNS server is not
available at all, the Ethernet module sends a service discovery request.
Note:
14, (15) and 16 will go on in a round robin way until the Ethernet module
has reached the server.