To properly check for noise buildup on a line you must check signal at the back of a modem FIRST, then back to the ground block and finally to the tap. If levels change significantly upon rechecking the modem before any changes to the line are made i.e. levels go for 57 on return to 45 on the return , you have NOISE BUILD UP so replace the drop or bad outlet.

  FUNCTIONALITY

• DOCSIS  (Data Over Cable Service Interface Specifcations)
  
  • DOCSIS 1.0 provides 5 megabits per second (Mbps) throughput or " true data rate " per 6 MHz channel over two-way HFC networks
    
  • DOCSIS 1.1 provides 10 Mbps
    
  • DOCSIS 2.0 provides up to 30 Mbps
    
  
  
• MAC  (Media Access Control )
  
  • Provides the procedures for transmission of data between the modem and CMTS
    
  • When modem is set to transmit, it addresses the MAC to request an open time interval or " mini slot"
    
  • This request includes the SID(Service ID)
    
  • From this request the MAC instructs the modem to send its data to the CMTS using a certin bandwidth and when
    THe MAC function set s limits for the amount of time the modem can use the channel to transmit packets, thus reducing packet collisions
    
  • WIthout MAC addressing modems would:
    
    1. Contend with one another over available time slots
    2. All colliding packets would have to be resent, further tying up the channel
  
  
• IP  ( Internet Protocal )
  
  • DHCP 
  • Static
  
  
• CMTS  (Cable Modem Termination System )
  
  • Before being sent downstream to a modem, the CMTS must pass through an RF upconverter to change signals to the appropriate radio freq
    
  • Has control over when each modem may transmit upstream to the node
    

  • CMTS FUNCTIONS
    
    1. Controls data receipt and retrieval
       
    2. Routing over the Internet
       
    3. Scheduling and timing
       
    4. Access to the RF network
       
    5. Processing
       
    6. Transmission
       
  • CMTS COMPONENTS
    
    1. A Modulator for processing downstream signals before transmission
       
    2. A Demodulator for processing upstream signals after reception
       
    3. A MAC Processor for managing modems and neighborhood nodes
       
    4. A Scheduler for managing flow of data traffic through the broadband network
       
  • CMTS PROTOCOLS
    
    • TCP/IP (Transmission Control Protocol / Internet Protocol
      • Provides basic protocols for directing traffic over the Internet
        
      • Tells network how to transmit packets of data and corects transmission errors along the way
        
    • PACKETS
      
      1. Numbered (packet sequence)
      2. Sized (data <1500 characters)
      3. Addressed both destination and return (destination address)
      4. Summed (checksum of data )
      • Not all packets are required to arrive at the same time in a transmission at the same instant (NOT TRUE IN VOIP )
      • If errors are found packets are resent over the network to replace corrupted ones
        
    • SNMP (Simple Network management Protocol)
      • Enables cable operators to configure, maintain , and monitor the preformance of CMTSs and modems (Agents) in the network
        
      • The NOC (Network Operations Center) polls an individual agents MIB (Management Information Base) and receives a status message from the agent
        
      • Doing this will help determine and correct any problems in the network
        
  
  
• OSS  (Operations Support System)
  
  • OSS servers routinely interface with network components to provide and/or receive the data required for proper network management
  • Account Management
    1. Determines customer usage of network by polling each modem or CMTS and provides records used in calculating monthly statements
       
  • Configuration
    1. Used in the initialization process including:
       
       • MAC protocol
       • DHCP (Dynamic Host Configuration Protocol)
         
       • TFTP  (Trivial File Transfer Protocol)
       • TOD  (Time of Day ) routing
  • Faults
    1. Handles detection, diagnosis, and correction of network problems
       
    2. Many of these faults are corrected without customer notification or service call
  • Performance
    1. Detects network speeds and manages throughput issues such as one way data loss, packet collisions, and completion for bandwidth (Contention )
  • Security
    1. Manages the policing or filtering of traffic so data reaches the appropriate IP address
    
    

1. CMTS: Equipment located at the headend or hub that manages the configuration of cable modems and their data trasnmitting and receiving.
   
2. Contention: A data enviroment in which many devices compete for the same time slots but only a limited number of devices can connect at one time. Devices that do not connect must try again later.
3. DOCSIS: A project that sets standards for equipment and processes for delivering high speed data over broadband cable networks. DOCSIS enables interoperability among cable modems and associated equipment by setting standars and operations support interface specifications.
4. DHCP: A protocol or set of instructions that enables a server to assign Internet protocol addresses to equipment in the network. These IP addresses are assigned dynamically by the DCHP allowing it to change addresses for the same equipment.
5. IP: A data oriented protocol used for communicating data across a packet switched internetwork. IP is a network layer protocol in the internet protocol suite and is encapsulated in a data link layer protocol. As a lower layer protocol, IP provides the service of communicable unique global addressing amongst computers.
6. LAN: A network that shares a common communications line linking together devices such as computers,printers, and other peripherals within a small geographic area such as an office or neighborhood.
7. MAC: The layer in a dat network that sits between the upstream and downstream sections of the cable modem and acts as the interface between the hardware and softwar portions of the various network protocols.
8. OSS: Processes that provide back office managment for the day to day functioning of the data network. These administrative processes are controlled by software on servers located at the headend or hub.
9. QoS: The measurement of performance of a broadband communications network.
10. SNMP: A protocol or set of instructions that enables the cable operator to cinfigure, maintain, and monitor the performance of cable modems and cable modem termination systems.
11. TOD: A server that provides a local or global date and time across the network so that equipment can synchronize accurate timing for procedures and data transfers.
12. TCP/IP:  Protocols or sets of instructions that direct data traffic over the Internet. TCP/IP tells the broadband cable network how to transmit packets of data and correct transmission errors along the way.
13. TFTP:  A protocol or set of instructions that enables equipment to access files on a server without the use of passwords or IDs.

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