User guide
Release9.5ReleaseNotes
Issue2,October2009 Page17
2.4 AP‐DHCPRELAY/OPTION82
The AP can now act as a DHCP relay for SMs and CPEs underneath it. The AP will make use of
the DHCP Option 82 (DHCP Relay Agent Information) from RFC 3046 when performing relay
functions. In this RFC, there are two sub options defined for DHCP Relay Agents to use to pass
useful information along to the DHCP server to identify from where the DHCP request is coming.
The sub options defined are used as follows:
1 – Circuit ID – This will contain the MAC address of the AP acting as the DHCP relay.
2 – Remote ID – This will contain the MAC address of the SM from or through
which the DHCP request was generated.
Also, in order to accommodate setting up pools or classes for different VLANs, the Option 82 field
will also include information to tell the server what VLAN the client is on. This Option 82 sub
option is adapted from the Vendor-Specific Information Sub-option in RFC 4243. This sub option
for Option 82 has the following format:
Figure 5: DHCP Relay Agent via Configuration => General on AP.
Configuring the DHCP Full Relay Operation will take broadcast DHCP packets and send them to
a Unicast server in unicast mode. This way the DHCP requests and replies can be routed like any
other UDP packet. A second configuration is to select Only Insert Option 82 which leaves the
DHCP request on its broadcast domain as opposed to DHCP Full Relay Operation which will turn
it into a unicast packet.
2.5 SM/BH–LARGEVCDATAQUEUE
Certain applications such as video Surveillance cameras operate by sending bursts of IP
traffic upstream. Some systems will send short bursts of packets at over 50 Mbps and then be
idle for some period of time and then send another burst of data.
In order for the RF interface of a radio to accommodate these bursts of traffic, there is now an
configurable parameter on SM radios as well as BH Master and Slave radios to operate with a
large input queue at the radio’s data VC. This large queue allows packets which arrive at a rate
greater than the radio link capacity to be stored in this deep queue until the radio is ready to
transmit them. The queue size has been optimized to allow large packets to be stored just long
enough so that there is always data available to be transmitted, but not large enough to cause
packets to sit in a queue for a second or more.
Configuration of this parameter is shown on the Configuration => Radio web page on the SM,
BHM and BHS. Operators should enable Large VC data Q on the BHM for downlink traffic or
enable it on the BHS for uplink traffic.