It’s All About Networking
Presented by
SCTE Desert Chapter
March 25th & 26th
Housekeeping
• Take this time to locate:
– Emergency Exits
– Bathrooms
– Breakroom/Water Fountain
– Note taking utensils
• Put your Phones on Vibrate
– If you need to take a call, feel free to step
out of the room.
About your Speaker
• Bryan Crisler
– Started in Cable @ Charter
Communications, Riverside, CA in June
2005
– Currently a Senior Network Engineer @
Time Warner Cable
About your Speaker
• Held following positions:
– Broadband Technician I-IV (Charter)
– Network Operations Specialist
(Charter)
– Network Technician (Charter)
– Network Engineer (Charter & TWC)
– SR Network Engineer (TWC)
Today’s Lesson Plan
• Session 1: The Basics of Networking
– 9:10 am - 10:00 am
• Session 2: The Basics of Networking @
Cable Company
– 10:10 am – 11:00 am
• Session 3: Troubleshooting Networking
Issues
– 11:10 am – 12:00 pm
Basics of Networking
Session 1
9:10 am – 10:00 am
What is Networking?
• Networking – a supportive system of
sharing information and services among
individuals and groups having a
common interest (dictionary.com)
What is a Computer Network?
• Computer Network – a group of
electronic devices interconnected for
the sharing of information, resources
(printers, scanners, etc), and services
(internet, email, etc)
• Each device on the network will
communicate with each other to share
information.
It’s Video Time!!!
• Check it out on youtube:
• http://youtu.be/Ve7_4ot-Dzs
Network Wiring
• Unshielded Twisted Pair (UTP
– CAT 5
• 4 pair (orange, green, blue, brown)
• Rated for 100 MBit/sec
– CAT 5e
• 4 pair (orange, green, blue, brown)
• Rated for 1000 MBit/sec
• More twists/inch than CAT5 – better noise reduction
– CAT 6
• 4 pair (orange, green, blue, brown)
• Rated for 1000 MBit/sec
• More twists/inch than CAT5e – best noise reduction
Network Wiring - cont
• Fiber
– Multi-mode (Orange)
• Short Range
• 1310 nano meters wavelength
– Single-mode (Yellow)
• Longer Range
• 1550 nano meters wavelength
• Capable of CWDM & DWDM
Different Types of Networks
• WAN (Wide Area Networks)
– A Network that spans geographical areas.
The internet is made up of many WANs
• LAN (Local Area Network)
– Smaller Network that is more
geographically focused.
– Most companies are made up of multiple
LANs
Network Models
• A conceptual networking model helps to
define the different functions of a
network.
• Allows various vendors to build network
devices while still keeping to the same
standard
• The Two most used models are TCP/IP
Model and the OSI Model
The OSI Model
The OSI Model – Host Layer
• Application (Layer 7)
– User Interface
– Used by services like Web (HTML), File Transfer Protocol, and
Telnet
• Presentation (Layer 6)
– Used to control Data sets like ASCII or UTF-8
• Session (Layer 5)
– Controls Session data and dialog control, if required.
– Used to establish Mode of transfer such as Full Duplex or Half
Duplex
• Transport (Layer 4)
– Provides end to end communication, error checking, and data
integrity
– Used by TCP and UDP
OSI Model – Media Layers
• Network (Layer 3)
– Used by Routers and some Multi-Layer Switches
– IP Address use to identify Network interfaces
– Encapsulates Data into Packet
• Data Link (Layer 2)
– Used by Routers and Switches
– MAC Address used to identify physical Hardware Interfaces
– Encapsulates Packets into Frames
• Physical (Layer 1)
– Used by the physical medium such as ethernet, fiber or coax
between all network devices.
– Uses bits to transfer frames across medium (1s and 0s)
What can you find in a Network?
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Routers
Switches
Hubs
Firewalls
Workstations (End Device)
Servers (End Device)
What is A Router?
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Layer 3 (Network Layer) Device
Connects WAN and LAN together
Allows access to Internet
Uses IP Address to Identify Network Interface
Shares routing information with other Routers
to determine best path.
• Can use Copper Twisted Pair, Fiber, or Serial
Connections to connect to other Routers or
Switches
What is a Switch?
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Layer 2 (Data Link) Device
Connects End Devices (CPEs) to a LAN
Allows Access to Local Services
Uses MAC Address to identify Physical Hardware
Interface
Employs Collision Detection and Full Duplex
communication for faster data transfer
Stores Known MAC Address into table for faster
lookup
Connects to Routers Upstream for Internet Access
Can use Copper Twisted Pair or Fiber to connect to
other Routers, Switches, or End Devices
What is A Hub?
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Layer 1 (Physical) Device
Connects End Devices (CPEs) to a LAN
Boost signal and retransmits data on all ports.
Older Technology, hardly used today.
Allows Access to Local Services
Connects to Routers Upstream for Internet
Access
• Can use Copper Twisted Pair or Fiber to
connect to other Routers, Switches, or End
Devices
What is a Firewall?
• A Layer 4/7 (Transport/Application) Device
• Configured with an IP Address
• Security Appliance that can prevent
unauthorized access by:
– Blocking IP Address (Sender/Receiver)
– TCP/UDP Port Number
– Packet Inspection (Layer 7/Application) Device
• May provide intrusion detection/prevention
• Network Address Translation
What is a Workstation?
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Layer 7 (Application) Device
End Device (CPE)
Receives IP Dynamically (DHCP) or Statically
Has a MAC Address for every Network
Interface Card
• Runs Windows, Linux, or MacOS
• Can be either Wired (Ethernet) or Wireless
• Can gain access to server as a client via
Application layer protocols such as Web, FTP,
SSH, Telnet, DNS, etc.
What is A Server?
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Layer 7 (Application) Device
End Device
Receives IP Dynamically (DHCP) or Statically
Has a MAC Address for every Network Interface Card
Runs Windows Server, Linux/Unix, or MacOS Server
Can be either Wired (Ethernet) using Copper or Fiber
Can provide servicess to clients via Application layer
protocols such as Web, FTP, SSH, Telnet, DNS, etc.
Network Topology Review
IP Addressing
• Layer 3 (Network) form of Addressing
• Two different forms of IP Address:
– IPv4
• Uses Dotted Decimal (192.168.0.1)
• Has 4,294,967,296 total address (public & private)
• 32 bit address
– IPv6
• Uses Hexidecimal Notation (FE80::1)
• Has 3.4×1038 total address (public & private)
• 128 bit address
IP Addressing - cont
• Both versions represent a real number
• For Instance:
– 0.0.1.0 = 256
– 10.0.0.4 = 16,777,220
– 0:0:0:0:0:0:0:1 = 1
– 0:0:0:0:1:0:0:0 = 281,462,092,005,375
IP Addressing - cont
• Blocks of IPs are called Subnets
• Each Subnet represents a network (either WAN or
LAN)
• The range of each subnet is determined by the
Subnet Mask
• Each Subnet has a Network (First IP address) and a
Broadcast (Last IP Address) IP Address
• Subnet Range is calculated Subtracting Subnet Mask
and from 255.255.255.255.
• For Example a Subnet Mask of 255.255.255.0 will
have 256 IPs in the Subnet
IP Address Example
• A home wireless Router is configured with
network address of 192.168.0.0 and a subnet
mask of 255.255.255.0
• 255.255.255.255 – 255.255.255.0 =
0.0.0.255 = 256 total address
• 192.168.0.0 + 0.0.0.255 = 192.168.0.255
• Network Range: 192.168.0.0 to
192.168.0.255
• Network Address: 192.168.0.0
• Broadcast Address: 192.168.0.255
IP Address - cont
• Network Address: First IP in a Subnet used to
identify the entire network
• Broadcast Address: Last IP in a Subnet used
to communicate any device on the Useable IP
Range.
• Gateway IP Address: The configured IP
address on the next hop router, which
contains a path towards a WAN/Internet
• Useable IP Range: Any IP in a subnet that
except the Network and Broadcast
MAC Address
• Layer 2 (Data Link) Address
• 48 Bit Address
• Identifies the Physical Hardware Address on a
Network Interface Card
• Uses a hexidecimal representation
• First 6 digits indicate a vendor oui.
• Example:
– 00:15:A4:00:11
– 00:e9:af:12:34
Resolving IP Address
• ARP – Address Resolution Protocol is
used to discover a MAC Address for a
specific IP Address by broadcasting a
message to everyone on a subnet using
a broadcast IP.
• rARP – Reverse Address Resolution
Protocol is used to discover the IP
Address for a specific MAC Address.
Public vs Private IP Space
• RFC1918 – Prohibits the distribution of private IP
Address space on WAN Links.
• Private Address Space includes:
– 10.0.0.0 – 10.255.255.255
– 172.16.0.0 – 172.31.255.255
– 192.168.0.0 – 192.168.255.255
• This space is specially reserved for private use only.
• Private space is was allocated to allow network
useable space, without having to allocate and waste
large blocks of public space.
• With Network Address Translation (NAT), private
space can be mapped to public space.
Dynamic Host Configuration
Protocol (DHCP)
• Allows a DHCP server to
assign/configure an IP Address to an
end device
• Will also configure Subnet Mask,
Gateway IP, as well as DNS Servers
• When an end device is configured for
DHCP, the DORA begins.
DHCP - cont
• DORA
– Discover – Client sends a message to DHCP Server
– Offer – Server sends a message to client with an
IP Address Offer
– Request – Client formally request IP Address
Offered, and sets Subnet Mask, gateway, DNS and
lease time
– Acknowledge – Server Acknowledges client
Request and reserves IP.
• Once lease is at half-life, DORA process is
repeated.
Domain Name Service (DNS)
• DNS – Maps a domain name like
google.com to an IP Address
• Multiple DNS servers are configured for
redundancy
• DNS Servers must be reachable in order
to be queried
Transmission Control Protocol
(TCP)
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Layer 4 (Transport) Protocol
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State Oriented Protocol
Reliable and Ordered Transmission
Provides Error Checking and Flow Control
Three Way Handshake to form socket
• Host A sends Syn
• Host B Sends Syn-Ack
• Host A send Ack
TCP Port Numbers reserved for well known services
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Web (HTTP) : 80
FTP : 20 & 21
POP : 110
IMAP : 143
SMTP : 25
Telnet : 23
SSH: 22
User Datagram Protocol (UDP)
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Simple transmission
Stateless protocol
No error checking or reliability
Used for Real-time transmissions such as
voice, streaming video, etc.
• Unidirectional communication
• UDP Port Numbers Reserved for Well known
services:
– tftp : 69
– Ntp : 123
Session 1 Review
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How many Layers are in the OSI Model?
How many bits are in an IPv6 Address?
What method is used by DHCP?
How is the Network Range determined?
Which device works at Layer 3 (Network)?
What is a Layer 2 Address?
How does a Layer 2 Address resolve a layer 3
address?
• Give me an example of a private address
• What is a Gateway IP Address?
Session 1 Q&A
• Any Questions???
Basics of Networking at a
Cable Company
Session 2
10:10 am – 11:00 am
What is DOCSIS?
• DOCSIS - Data Over Cable Service
Interface Specification – Allows network
connection over RF Cable using cable
modems and a CMTS
History of DOCSIS
• DOCSIS was developed by CableLabs and a
consortium of other vendors
• DOCSIS 1.0
– Released in March 1997
• DOCSIS 1.1
– Released in April 1999
• DOCSIS 2.0
– Released in December 2001
• DOCSIS 3.0
– Released in August 2006
• DOCSIS 3.1
– Release in October 2013
DOCSIS Terminology
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DS – Downstream
US – Upstream
CM – Cable Modem
CPE – Customer Premise Equipment
TDMA – Time Division Multiple Access
– Allows multiple modems to register to a single interface
• Mac Domain – a single service group of multiple DS and US
channels. A single Mac Domain may feed one or multiple
RF/Fiber Nodes
• Channel Width – The width of a single channel in Hertz. US
Channel widths range from 200 kHZ to 6.4 MHz, whereas DS
Channel width is fixed at 6MHz
• Channel Modulation – A specific way that a channel signal is
transformed, typically either QAM or QPSK
DOCSIS 1.0/1.1
• Supported 1 DS Carrier
– Channel Width: 6 MHz
– Channel Modulation: 64 QAM / 256 QAM
– Maximum Speed: 42.88 Mbits/sec
• Supported 1 US Carrier
– Channel Width: 200 kHz – 3.2MHz
– Channel Modulation: QPSK / 16 QAM
– Maximum Speed: 10.24 Mbits/sec
DOCSIS 2.0
• Supported 1 DS Carrier
– Channel Width: 6 MHz
– Channel Modulation: 64 QAM / 256 QAM
– Maximum Speed: 42.88 Mbits/sec
• Supported 1 US Carrier
– Channel Width: 200 kHz – 6.4MHz
– Channel Modulation: QPSK / 8 QAM - 64 QAM
– Maximum Speed: 30.72 Mbits/sec
DOCSIS 3.0
• Supported 24 DS Carrier
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Supports DS Channel Bonding
Channel Width: 6 MHz
Channel Modulation: 64 QAM / 256 QAM
Maximum Speed: 1029.12 Mbit/ sec
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Supports US Channel Bonding
Channel Width: 200 kHz – 6.4MHz
Channel Modulation: QPSK / 8 QAM - 64 QAM
Maximum Speed: 245.76 Mbits/sec
• Supported 8 US Carrier
DOCSIS 3.1
• Supported Unlimited DS Carrier
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Supports DS Channel Bonding
Channel Width: 20 kHz – 50 kHz OFDM
Channel Modulation: 256 QAM / 4096 QAM
Maximum Speed: 10 Gbit/ sec
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Supports US Channel Bonding
Channel Width: 200 kHz – 6.4MHz
Channel Modulation: QPSK / 8 QAM - 128 QAM
Maximum Speed: 1 Gbits/sec
• Supported Unlimited US Carrier
What is a CMTS?
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CMTS – Cable Modem Termination System
A Layer 3 (Network) Device
Has similar functions to that of a Router
Connects to other Routers using Fiber or Copper UTP
Provides a shared RF Connection to a fiber-node
(service group/mac-domain) that will service upto
250 customers (on average)
• Uses DS Frequencies between 85MHz – 1 GHz and
US Frequencies between 5-85 MHz to communicate
to Cable Modems (DOCSIS 3.0 Spec)
What is a CMTS? - cont
• CMTS in production:
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Cisco uBR 10012
Arris C4
Arris E6000
Casa 10G
Motorola BSR 64000
What is a Cable Modem?
• A network bridge that provides network
access via RF channels. Delivers
broadband access and speeds upto
1Gbit/sec and 200Mbit/s
• Layer 2 (Data link) Device
• 1 RF Connection, 1 Ethernet Connection
• May have CPE such as STB, VoIP or
Home Wireless Router attached
How do modems connect to the CMTS?
Modem/CMTS Messaging
• SYNC – Timing Synchronization
– sent every 200 ms
• UCD – Upstream Channel Descriptor
– Provides the upstream frequency of which the
modem will reply back on, along with symbol rate,
modulation, etc.
• MAP – Media Access Protocol
– Allocates set communication interval for each
modem.
• RNG-REQ – Range Request
• RNG-RSP – Range Response
Modem/CMTS Messaging - cont
How Modems Register
How Modems Register - cont
How Modems Register - cont
How Modems Register - cont
Cable Modem Addressing
• Each cable modem has two primary
addresses:
– MAC Address (CMAC/RF/DOCSIS, etc)
– IP Address
• Typically will be a private IP Address
• Acts as a bridge for Inbound and Outbound
network traffic
CPE Addressing
• Each CPE has two primary address:
– MAC Address
• If you CPE is attached to a modem it may be a
STB, VoIP, MTA, CPE MAC
– IP Address
• Depending on the service, this may or may not
be a private IP Address.
• This address will provide access to the
necessary services
Session 2 Review
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When was Channel Bonding Introduced?
What is TDMA?
What is a UCD and what does it contain?
What is a Cable Modem?
What is the channel width of a DS Carrier?
IS the ip address of a cable modem typically
public or private?
• What three Layers of the OSI model does a
CMTS Operate on?
Session 2 Q&A
• Questions?
Basic Network
Troubleshooting
Session 3
11:10 am – 12:00 am
IPConfig
• Run cmd
• Type ‘ipconfig /all’
– Displays all IP Addresses
• Type ‘ipconfig /release’ & ‘ipconfig /renew’
– If you need to refresh the IP with the DHCP
Server do a /release & /renew
• Type ‘ipconfig /flushdns’
– If you are having problems reaching some
websites, run a /flushdns
Tracert (Traceroute)
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Run cmd
Shows latency and hopcount
Each hop is a router interface
Maximum hops on tracert is 30
Type ‘tracert google.com’
– To see if you can reach google or any other domain name.
• Type ‘tracert 4.2.2.2’
– If you are unable to resolve any DNS, you can still traceroute using
an IP Address
• Type ‘tracert 192.168.1.1’
– If you are trying to reach your local router’s gateway ip address
• Type ‘tracert <cpe gateway ip>’
– If you are trying to reach your CPE gateway IP Address on the
CMTS.
Ping
• Run cmd
• Great test for packet loss
• Type ‘ping google.com’
– To see if you can reach google or any other domain name
• Type ‘ping –t <ip or domain name>’
– To test for packet loss on the internet. –t will continuosly
ping until cntr-c is pressed.
• Type ‘ping –n <count> <ip or domain name>
– To test for packet loss with a specific amount of packets.
• Type ‘ping –l <size of packet> <ip/domain>
– To test for packet loss with a greater packet size.
NSLookup
• Run cmd
• Used to query DNS Server and perform DNS Lookups
• Can be used to determine if DNS server is down or
not reachable
• Type ‘nslookup google.com’
– Performs a standard lookup
• Type ‘nslookup <ip address>’
– Performs a reverse dns lookup to find domain name
• Type ‘nslookup <ip/domain> <server ip>’
– Performs a lookup using a different server
Network-tools.com
• Goto www.network-tools.com
– Many different network tools
– Allows you to ping from outside cable
network
– Can check DNS Records
– Can also check email spam blacklists
Wireless Troubleshooting
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Check SSID
Verify Security is using WPA2
Set DHCP leases to 10
Setup MAC Filtering
Session 3 Q&A
• Any Questions???