We assume that a client requesting to establish a channel from a
source 
is given a route by the routing subsystem. It
then issues an establish request message that travels along that
route to all d receivers 
. In the
first pass, the traffic parameters of the connection, such as
, are passed along the given route as part of
the establish request message, which is replicated at each
branch node it encounters on its path, and sent down each of the
branches of that subtree.
At each node, admission tests are performed based on the parameters in the establish request message sent from the source. For the case of RCSP, the admission control decision is based on Equation (1). In this first pass, the connection is assigned the highest available priority. In a branch node, the admission tests are performed for each subtree separately. So the allocated priority level may be different for the different outgoing links of a node, according to the resource availability. If all priority queues are full, the connection request is rejected. We note that, in this case, the available bandwidth of the link would be exceeded.
To determine whether enough buffer space is available at the local node, the following equation can be used,
where 
is the local delay bound of the priority level
assigned to the connection on the predecessor, and 
is the
local delay bound on the current node. If 
exceeds the
currently available buffer space, the connection is rejected.
If any of the tests fails, a channel-reject message is sent back
upstream nodes, and the tentative resource reservations for this
connection are canceled. If all tests are successful, the
establish request message is forwarded down the multicast route until
it arrives at a receiver. Every node keeps track of the
cumulative delay, which is the sum of the local delays from the
source to the node. If 
is the local delay of output
link from 
to 
, the cumulative delay at Node
can be represented as follows:
During the request pass, each node on the route is passed the cumulative delay of its predecessor in the route as part of the establish request message. This allows the node to calculate its own cumulative delay, which is then forwarded to the descendants.
When the establish request message reaches a destination, a
final acceptance test is performed. As part of it, the cumulative
delay is compared against the end-to-end delay bound D. If
at a destination node 
,
the connection is accepted, otherwise rejected, in which case the
establishment process is aborted by sending a establish reject
message sent upstream to the sender.