L-INX User Manual
194
LOYTEC
Version 4.0
LOYTEC electronics GmbH
Whether enabled or disabled, out-of-sequence packets are never sent to the CEA-709
channel. Please refer to Section 4.2.7 on how to enable or disable escrowing.
7.5.5 SNTP Time Server
Small IP networks like LANs have a small propagation delay for packets traveling in these
networks. In this case it is not necessary to specify an SNTP server.
In larger IP-852 networks like the Internet with possibly long packet delays, one must
specify an SNTP server to synchronize the local clocks of the CEA-852 devices. The local
clocks must be synchronized to a common notion of time in order to make CEA-852
protocol features like Escrowing (Channel Timeout) work properly.
The SNTP timeserver can be specified on the IP-852 channel level in the configuration
server, which distributes the timeserver address to all CEA-852 devices on the IP-852
channel.
A primary and a secondary SNTP server can be defined please refer to Section 4.2.7 and
Section 4.2.9 on how to enable the SNTP server.
7.6 Advanced Topics
7.6.1 Aggregation
Aggregation (or packet bunching) is a technique that collects multiple CEA-709 packets
into a single larger IP packet. Aggregation improves overall system performance since one
IP-852 packets, now carries multiple CEA-709 packets und with the same number of IP-852
transactions, more CEA-709 packets can be exchanged between CEA-852 devices thus
reducing protocol overhead. The Aggregation Timeout defines the time period in ms in
which the transmitting device collects the CEA-709 packets before it transmits the CEA-852
packet over the IP-852 channel. Please refer to Section 4.2.7 on how to enable aggregation.
Note, that aggregation adds a delay to the transactions but dramatically improves the
throughput of your IP-852 channel. Use aggregation if you have a high channel load but can
tolerate some additional propagation delay given by the aggregation time value.
7.6.2 MD5 Authentication
MD5 authentication is a method of verifying the authenticity of the sending device. Only
devices that have MD5 enabled and use the same MD5 secret can share information with
each other. If the configuration server has MD5 enabled, only devices that have MD5
enabled and use the same MD5 secret as the configuration server can join the logical IP-852
channel. Please refer to Section 4.2.7 and 4.2.9 for details.
7.6.3 Dynamic NAT Addresses
A common practice for Internet providers is to assign addresses on a per-session basis to a
client. Each time a connection is established (e.g., an ADSL link is set up), the Internet
provider may choose an IP address from a pool. Since this address will be the public
address of a NAT router, the NAT address configured in the device would need to be
updated. The Auto-NAT feature in the device permanently monitors the current NAT
address. When the device detects a change in the NAT address it re-registers with the
configuration server using this new address. This feature requires a LOYTEC configuration
server (e.g., LINX-101, L-IP) and ―Roaming Members‖ enabled on that CS.
A consequence of this monitoring process is that the device contacts the CS every 45
seconds to probe for the NAT address. This causes a small amount of additional traffic on
the Internet link. The Auto-NAT feature also causes any shut-down connection to be re-
established. The NAT monitoring functions as a keep-alive for the connection. If neither the
additional traffic nor the automatic initiation of a new connection is tolerable, the Auto-
