Juniper CTP Series User Manual

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In a serial both-ended Y-cable redundancy configuration (software-based Y cable link
protocol), removal of Y cable leg from the CTP port of the online bundle must be able
to force a switch to the standby bundle.
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In a T1/E1 both-ended Y cable configuration (software-based Y cable link protocol),
removal of Y cable leg from the CTP port of the online bundle must be able to force a
switch to the standby bundle.
The T1/E1, CTP, and SAToP bundles support LOS detection and based on this signal, the
run state of the bundles switches to TfFail, which initiates a software-based Y cable
switchover to a redundant port. Also, for T1/E1 both-ended Y-cable redundancy
configuration, only software-based Y cable link protocol is supported and hardware-based
redundancy is not supported.
The way in which CTP redundancy works is by using the bundle state to make decisions.
When a bundle is in the RUNNING state, the following processes occur:
1. The remote CTP is operational and is able to generate and send packets into the IP
network (towards us).
2. The network is able to transport bundle OAM and payload packets from the remote
CTP to the local CTP.
3. A sufficient percentage of the bundle payload packets fills packet delay variation
(PDV buffers) and maintain circuit data transport towards the locally connected user
equipment.
Therefore, when a bundle is in the RUNNING state, it is “usable” and can be online in a
redundant configuration.
Consider a network topology in which a failure occurs in the circuit path that does not
cause the circuit to exit the RUNNING state. This phenomenon can be the case when the
cable is pulled from the CTP port of a redundant online bundle. Although this condition
might not typically be considered an actual failure, and instead more of a configuration
error, this symptom can nevertheless be classified in the failure category. Therefore, a
mechanism to be able to detect this condition in redundant setups and provide an online
circuit switch to offline when the cable is removed is beneficial. CTP devices support the
evaluation of LOS conditions on serial interfaces and T1E1 interfaces in CTP bundles and
SAToP bundles.
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Detection of LOS on Serial Interfaces on page 130
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Detection of LOS on T1/E1 Interfaces on page 131
Detection of LOS on Serial Interfaces
For serial interfaces, the determination of LOS condition is already performed in CTPOS
releases earlier than Release 7.2R1. When a serial circuit is configured to use the TT input
(on a data communication equipment [DCE] interface) for at least one of its five
configured port clocks (for example, “Cfg Rate - Ext Clk), the external clock frequency is
examined by the CTP device before the local bundle can go to the running state. If there
is no external clock present or it is not the correct frequency, then the bundle transitions
to the TtFAIL state and never go to RUNNING. Also, if the bundle is already in the RUNNING
Copyright © 2018, Juniper Networks, Inc.130
Using Bundles to Create Logical Configurations for Physical Interfaces, CTP Release 7.3, CTPView Release 7.3

Juniper CTP Series Specifications

General

Brand	Juniper
Model	CTP Series
Category	Server
Language	English