MONITORING OF NON-SNMP BASED NODES IN FTTC NETWORK.
In Fiber to the Curb (FTTC) network Cable Modem Terminating (CMTS) nodes are attached to the central location plant. If these nodes have Simple Network Management Protocol (SNMP) capabilities then it can be monitored easily from central operation and maintenance center called Network Monitoring System (NMS). In field many non-SNMP based nodes are deployed which cannot be monitored directly. This paper proposes a method of adding some hardware modems servers and software tools which will add a cost effective nodes monitoring capability. This paper will show deployment of the modems server specification and detailed monitoring graphs to prove validity of the proposed method.
Keywords: FTTC CMTS SNMP SNR Solarwinds Orion Cacti
SNMP is primarily used for device-based management and was designed to be as non-invasive as possible . An important requirement for SNMP is to minimize the managed element processing overhead. SNMP was therefore designed to collect and report information but not to provide the valuable information processing. For instance an SNMP- managed node does not report information like link throughput on the other hand SNMP defines the information which is to be collected and it relies on the NMS to retrieve and process the required information to produce a derived value. Fig. 1 shows typical setup of SNMP based monitoring setup.
Hybrid fibre-coaxial (HFC) is a telecommunications industry term used for FTTC and such a network incorporates deployment benefits in terms of flexibilities to carry high data rate media comprising both optical fibers and coaxial resulting in a broadband network . It is commonly employed by cable TV operators with additional data carrying capabilities.
Older CAT-V systems were provisioned and designed for coaxial cables only. Whereas modern systems use the fiber transport right from the Headend exactly to an optical node located in somewhere in the neighborhood of customers and thus the outcome is reduced system noise and it carries signal further beyond the capabilities of coaxial cable . The fiber plant is generally a star configuration with all optical node fibers terminating at a headend. The coaxial cable part is generally a trunk and branch configuration . HFC network can carry many types of services which includes digital TV analog TV and high definition television (HDTV) the video on demand (VOD) variety of switched digital videos the common telephony and high-speed data  .
A fiber optic node has a broadband optical transmitter and the receiver capable of converting the downstream optically modulated signal coming from the headend to an electrical signal going to the homes r offices as well as electrical signals from the home or offces into optical signals in the reverse path. In new systems this very downstream electrical output is the radio frequency which is a modulated signal
that generally ranges from the 50 MHz upto the 1000 MHz. Fiber optic cables connects the optical node to a distant headend or hub in a point-to-point or the star topology or in some cases in a ring topology having protection paths. The fiber optic node also contains a reverse path transmitter that sends communication from the home or offices back to the headend . So in case of VOD service the reverse pat is used for customers to make a demand for video service. The upstream frequency typically ranges from 5 to 42 MHz.
Cable Modem Termination System (CMTS) is the central device for the connection of cable TV network to a data network e.g. the internet. It is normally placed in the headend of the cable TV system .
A cable modem termination system (CMTS) equipment is most of the cases found in a cable company's headend or at the cable company hubsite. It efficiently provides high speed data services such as internet and the voice over IP (VoIP). For providing these high speed data services a cable company connects the headend to the Internet backbone via very high capacity data links to one or more network service providers. While on the subscriber side the CMTS maintains the communication with the subscribers' cable modems. Different CMTS based solutions are capable of serving a variety of cable modem population sizes and surprisingly these ranging from the 4000 cable modems to 150000 or even more in some cases. CMTS can be imagined like a router with a Ethernet interfaces on one side and the coax RF interfaces on the other side . The coax/RF interfaces carry RF signals towards and from the subscriber primises cable modem.
2. ROLE OF CABLE MODEM
All the modems have to register themselves to the HFC network before it can communicate with the network . This is done in a simple few steps explained below .
When the modem is powered on it first scans a set of Frequencies which are already broadcasted by the CMTS. When the desired frequency is acquired by the modem it locks it up and then sends its own frequency at which the data is sent by the cable modem. This very frequency is known as upstream frequency.
Offline shows that the modem is turned OFF Ranging means it is scanning for the downstream/upstream frequencies.
DHCP Discovery; in this state the IP addresses are assigned. It consists of two states which are DHCP discovery and DHCP acquired
TFTP shows that the TFTP server is sending any file to the cable modem.
Registered this state mentions that the modem is ready to operate and it has completely acquired all the settings.
3. PROBLEM STATEMENT
Any deployed system does not have SNMP supported nodes. So in case of outages problems are escalated directly by the customer and the technical team sitting in the OMC cannot instantly detect the fault. As costly solution is that to go for a SNMP supported nodes and discard the old ones. But surely it involves money so it is not a catching idea. I am proposing an idea which has been tested in the field and with a trivial investment nodes can be monitored easily. Technical teams sitting in NMS can detect faults instantly and proper rectification or instant escalation of the fault is possible.
4. PROPOSED SOLUTION
Nodes monitoring comes through IP based modems installed within nodes covered area and these modems would give their output to Cacti and Orion servers and the Solarwind NPM  .
The servers are used to monitor test modems installed on node server monitor in the NMS so that network monitoring of nodes becomes possible.
4.1. ORION / CACTI / SNMP TRAFFIC GRAPHER
In Orion server nodes monitoring comes through a server as shown in Fig. 6. Different nodes were placed at different areas and the green color light mentions their powered up status while reds color lights are showing the powered off nodes in the Orion server.
It provides automatic discovery and the wizard-driven configuration which offer. After installing SolarWinds NPM  it can then monitor the critical network devices which is in this case a cable modem placed at the node side.
The SolarWinds interface provides the monitoring capabilities with a minimal configuration overhead and thus make it user friendly.
The cost and the maintenance of SolarWinds installation is comparatively very less than the initial cost of most the other solutions. It provides individual polling engines which in turn scales the SolarWinds NPM installation to any environment. By sharing the same database it provides sharing of a unified user interface thus it makes the addition of polling engines transparent to the NMS technical staff.
As shown in Fig. 5 nodes are being monitored through intelligent network where nodes position could be checked that whether it is in off state or in on state. Furthermore we have IP address against any node by taking mouse pointer at node thus IP address will be shown and this address will put on cactus server and set parameters of request. By putting address from the Fig. 6 we can see a window of graph showing traffic (downstreamand upstream) against IP address. From SNMP traffic graph shown in the Fig. 8 traffic against node can be noted and any traffic outage can be seen which will indicate the problem at the node end.
The dialog box shown in Fig 7 is used for settings for SNMP TrafficGrapher. The default settings can be changed with the ones shown on the right and this change is recommended too. The red box shows the entry area where the target IP address should be inserted.
Single graph displays the changes in two configurable SNMP variables with the display of Current Average and the Maximum values. Rate of flow of data on any particular IP interface is plotted versus time. By default the blue graph shows downstream and the green graph shows upstream of data but this setting can be amended.
The graphs shown give validity that monitoring of the FTTC nodes is now quite possible despite the fact they don't support direct SNMP. Many traffic reports can be generated by the mentioned interfaces. In case of node failure the node will be shown red and the NOC staff will know about the outage within no time. This solution was tested on live system for several months and it proved to be quite valid.
We are grateful to Mr. Wajeeh-ul-Hassan of Harwa
Technologies Lahore Pakistan for assisting us in this project and for helping us in compiling all the results. I am personally grateful to the technical team of Harwa Technologies for helping in deployment of the mentioned solution and the related field testing; and their sharing of all the findings on regular basis.
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