It’s All About Networking

Presented bySCTE 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 19:10 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?• Routers• Switches• Hubs• Firewalls• Workstations (End Device)• Servers (End Device)

What is A Router?

• 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?

• 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?

• 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?

• 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?

• 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)• Layer 4 (Transport) Protocol

– 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– Web (HTTP) : 80– FTP : 20 & 21– POP : 110– IMAP : 143– SMTP : 25– Telnet : 23– SSH: 22

User Datagram Protocol (UDP)• 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

• 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 210:10 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• 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– Supports DS Channel Bonding– Channel Width: 6 MHz– Channel Modulation: 64 QAM / 256 QAM– Maximum Speed: 1029.12 Mbit/ sec

• Supported 8 US Carrier– Supports US Channel Bonding– Channel Width: 200 kHz – 6.4MHz– Channel Modulation: QPSK / 8 QAM - 64

QAM– Maximum Speed: 245.76 Mbits/sec

DOCSIS 3.1

• Supported Unlimited DS Carrier– Supports DS Channel Bonding– Channel Width: 20 kHz – 50 kHz OFDM– Channel Modulation: 256 QAM / 4096 QAM– Maximum Speed: 10 Gbit/ sec

• Supported Unlimited US Carrier– Supports US Channel Bonding– Channel Width: 200 kHz – 6.4MHz– Channel Modulation: QPSK / 8 QAM - 128

QAM– Maximum Speed: 1 Gbits/sec

What is a CMTS?

• 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:– 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

• 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 311:10 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)• 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

• 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

• Check SSID• Verify Security is using WPA2• Set DHCP leases to 10• Setup MAC Filtering

Session 3 Q&A

• Any Questions???