Transition Networks, Inc.
S4224 Web User Guide
33595 Rev. C
Page 658 of 669
QCL
QCL (QoS Control List) is the list table of QCEs, containing QoS control entries that classify to a specific QoS
class on specific traffic objects. Each accessible traffic object contains an identifier to its QCL. The privileges
determine specific traffic object to specific QoS class.
QL
QL, in SyncE, is the Quality Level of a given clock source. This is received on a port in a SSM indicating the
quality of the clock received in the port.
QoS
QoS (Quality of Service) is a method to guarantee a bandwidth relationship between individual applications or
protocols. A communications network transports a multitude of applications and data, including high-quality
video and delay-sensitive data such as real-time voice. Networks must provide secure, predictable, measurable,
and sometimes guaranteed services. Achieving the required QoS becomes the secret to a successful end-to-
end business solution. QoS is the set of techniques to manage network resources.
When discussing QoS features:
• "Packets" carry traffic at Layer 3.
• "Frames" carry traffic at Layer 2 (Layer 2 frames carry Layer 3 packets).
• "Classification" is the selection of traffic to be marked.
• "Marking" (per RFC 2475) is the process of setting a Layer 3 DSCP value of a packet.
• "Policing" is limiting bandwidth used by a flow of traffic; policing can either mark or drop traffic.
R
R-APS
R-APS is an acronym for Ring APS. Per G.8032v1, in ERPS there is a central node called the ‘RPL Owner
Node’ which blocks one of the ports to ensure that there is no loop formed for the Ethernet traffic. The link
blocked by the RPL Owner node is called the Ring Protection Link or RPL. The node at the other end of the
RPL is known as RPL Neighbour Node. It uses R-APS control messages to coordinate the activities of switching
on/off the RPL link.
Any failure along the ring triggers an R-APS(SF) (R-APS signal fail) message along both directions from the
nodes adjacent to the failed link after these nodes have blocked the port facing the failed link. On obtaining this
message, RPL owner unblocks the RPL port. Note that a single link failure anywhere in the ring ensures a loop
free topology.
During the recovery phase when the failed link gets restored, the nodes adjacent to the restored link send R-
APS (NR) (R-APS no request) messages. On obtaining this message, the RPL owner blocks the RPL port and
then sends a R-APS (NR,RB) (R-APS no request, root blocked) messages. This causes all other nodes other
than the RPL Owner in the ring to unblock all of the blocked ports.
This protocol is robust enough to work for unidirectional failure and multiple link failure scenarios in a ring
topology. It allows mechanism to force switch (FS) or manual switch (MS) to support field maintenance
scenarios.
R-APS virtual channel
The Ring Automatic Protection Switching (R-APS) channel connection between two interconnection nodes of a
sub-ring in (an)other Ethernet ring(s) or network(s). Its connection characteristics (e.g., path, performance, etc.)
are influenced by the characteristics of the network (e.g., Ethernet ring) providing connectivity between the
interconnection nodes. From ITU-T Rec.G.8032/Y.1344 (03/2010).
RARP
RARP (
R
everse
A
ddress
R
esolution
P
rotocol) is a protocol used to obtain an IP address for a given hardware
address, such as an Ethernet address. RARP is the complement of ARP.
RADIUS
RADIUS (
R
emote
A
uthentication
D
ial
I
n
U
ser
S
ervice) is a networking protocol that provides centralized access,
authorization and accounting management for people or computers to connect and use a network service.
