PCoIP Technology User Guide
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endpoints can advertise to the primary CMS
first, and in the event of a transmit failure,
advertise to a secondary CMS.
Unlike Service Location Protocol, DNS-SRV
discovery does not use multicast IP traffic. As a
result, it works across subnets. Routers are
typically configured to block multicast IP traffic
by default, so the CMS cannot use SLP to
discover endpoints located on different subnets.
DNS-SRV provides a standardized approach for
the endpoint to query the DNS server for a CMS
service.
Requirements
DNS-SRV discovery requires that:
•
DNS zone data must have a DNS-SRV RR in
the format described by RFC 2782:
_Service._Proto.Name TTL Class
SRV Priority Weight Port Target
where:
_Service=_pcoip-broker,
_Proto=_tcp,
Name = hierarchical domain name
•
Endpoints must have access to a DHCP
server in order to get the domain name and
hostname (to get DHCP options 15 and 12,
respectively).
•
The DHCP server must support either DHCP
option 12 (hostname), 15 (domain name), or
both. If the server supports only option 12, the
hostname string must contain the domain
name.
Discovery Using SLP (Service
Location Protocol)
The endpoint can be configured to use SLP
(Service Location Protocol) discovery. How the
endpoint uses SLP discovery depends on
whether the deployment is managed or
unmanaged.
In unmanaged deployments:
•
Host and Portal advertise services so that
another network SLP-aware entity can
discover the endpoint.
•
When host discovery is enabled on a Portal,
the Portal dynamically discovers Hosts.
In managed deployments:
•
The Host and Portal advertise services so the
CMS can discover the endpoint.
The endpoint uses the Service Location Protocol
SLPv2 as defined in RFC2608. The endpoint
advertises a service to either an SLP directory
agent or an endpoint/CMS (if a Directory Agent
is not present).
SLP over Multiple Subnets
When endpoints, CMS (if present), and Directory
Agent (if present) are on the same subnet, SLP
uses multicast/broadcast SLP messaging to
register and discover service locations.
However, when any endpoint or CMS is on a
different subnet, routers must be configured to
allow packets destined for the SLP multicast
group 239.255.255.253 to pass.
Multicast reduces network congestion by
directing SLP messages to endpoints registered
with the standard SLP multicast group. The
endpoint uses IGMP (Internet Group
Management Protocol) to “join” the standard
SLP multicast group. Packets sent to IP address
239.255.255.253 are multicast to the endpoints
registered with the group.
A User Agent multicasts a service request (to
the SLP multicast group) and a Service Agent
responds via a unicast connection. If the PCoIP
System is deployed over multiple subnets, the
multicast-enabled routers must not filter packets
destined for the SLP multicast group.
