Notes 01‐1 - LPouliot/Junior-Spring-NET-330-01-Network-Design GitHub Wiki
Week 1 Notes | IP Addressing Review
Sending a Letter vs. Sending a Packet
Letter
Look up recipient address
Phone Book? Other Directory?Get zip code and street address
Put in addressed envelope
Write recipient and return address on envelope
Put letter in mailbox
Mail carrier picks letter up
Takes letter to local post office
Post Office sorts and sends to next PO facility
Uses zip code
How does PO know where to send next?
Postal Service has “routing lists”
Ends up at local PO of recipient
Mail Carrier delivers to recipient
Uses street address
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Network Data
Look up recipient address
Domain Name System (DNS)Convert Hostname to IP address
Add “headers” to data (encapsulate)
Prepend bits for recipient and sender IP address to data
Send packet to network interface controller (NIC)
Transmits onto network
Sent to local router (aka Default Gateway)
Router sends packet to next router
Uses Network part of IP address
How does router know where to send next?
“Routing table” of IP networks
Ends up at local router of recipient
Router and switches send to recipient
Uses Host part of IP address and MAC address
OSI Model
Open Systems Interconnection (OSI) is a network protocol framework that uses 7 layers
The 7 layers define the different stages that data must go through to travel from one device to another over a network
OSI Model – Letter Analogy
Application Layer (Layer 7)
- Network: The data that the computer is sending/receiving
“I would like to view the webpage www.google.com”
- Letter: The body of the letter
“To whom it may concern, I would like to commend your organization for the excellent service I received….”
Presentation Layer (Layer 6)
- Network: Compression, encryption, other encoding
- Letter: Is it in code, abbreviated (texting?)
Session Layer (Layer 5)
- Network: Session set up and teardown
- Letter: Tracking Number
Transport Layer (4)
- Network: Port numbers tell receiver what application the data is for
Port 80 – HTTP web traffic
Port 25 – SMTP e-mail
Port 22 - SSH
- Letter: Internal routing info on envelope
Suite 36
Dept. C9
Network Layer (3)
- Network: IP addresses of sender and receiver
- Letter: Street address and zip code of sender and receiver
Data Link Layer (2)
- Network: Defines how the packets get onto the media
When is it safe to send – prevent collisions
Is the recipient ready to receive
- Letter: How do you get it to the postal service?
Carrier pick up from your mailbox
Take it to Post Office
Drop it in mailbox
Physical Layer (1)
- Network: Physically send the bits over media
Copper wires
Fiber optic
Radio waves
- Letter: What service to use
USPS
UPS
FedEx
Network Addressing
3 components to a computers network address
- Network ID: First part of IP Address
- Think ZIP Code
- Host ID: Second part of IP Addres
- Think street address
- MAC Address: Unique to every network adapter
- Also like a street address
Network Addressing: IP Address
32-bit number
Typically displayed as four 8-bit numbers with dots in between
- called dotted decimal notation
- Each 8-bit number is called an octet
Binary IP Address:
- 10000001101010100001001011011100
Translated to dotted decimal:
- 129.170.18.220
IP Address includes both the Network ID (zip code) and Host ID (street address)
Net ID is always at the beginning
Tricky bit:
- IP address is always 32 bits but…
- Net ID can be different lengths – anywhere from 8 to 30 bits.
- Host ID is whatever is left over
- Subnet Mask – defines how many bits are in the Net ID
Example:
Binary IP Address:
- 10000001101010100001001011011100
Translated to dotted decimal:
- 129.170.18.220
Subnet mask is /24
- Means first 24 bits are Network ID
So,
- Network ID is 129.170.18
- Host ID is 220
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An organization “owns” 129.170.0.0/16
This means they can assign any IP address from 129.170.0.1 to 129.170.255.254
Subnet Masks also written in dotted decimal
- /16 is also 255.255.0.0
- /24 is 255.255.255.0
- Basically – all 1’s for the Network ID
Anatomy of an IPv4 Address
Each device on a network must be uniquely identified at the Network layer.
For IPv4, a 32 bit source and destination address is contained in each packet.
Anatomy of an IPv4 Address
Devices use binary logic and work with strings of binary numbers. For us, the decimal equivalent is much easier to use and remember.
To identify a path or "route" through a network, the address must be composed of two parts:
- Network portion
- Host portion
Network Portion:
- Some portion of the high-order bits represents the network address.
- At Layer 3, we define a network as a group of hosts that have identical bit patterns in the network address portion of their addresses.
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Host Portion:
- There are a variable number of bits that are called the host portion of the address.
- The number of bits used in this host portion determines the number of hosts that we can have within the network.
Types of Addresses in an IPv4 Network Range
Three types:
Network and Broadcast addresses
CANNOT
be assigned to a host.
Network Address
Standard way to reference a network (Lowest Address).
All hosts in the network will have the same network bits.
Cannot be assigned to a device.
Each host bit in this address will be 0.
Broadcast Address
The destination address of a single packet used to communicate to all hosts in a network (Highest Address)
Cannot be assigned to a device.
Each host bit in this address will be 1.
Host Address
The unique address assigned to each device on the network.
Assign any address between the network address (192.168.10.0) and the broadcast address (192.168.10.255).
Addresses 192.168.10.1 through 192.168.10.254.
Types of Communication in an IPv4 Network
Unicast Communications
The process of sending a packet from one host to an individual host.
Broadcast Communications
The process of sending a packet from one host to all hosts in the network.
Broadcasts are not forwarded by a router unless specifically configured to do so.
The bits in the host portion of a broadcast address will be all 1s.
Multicast Addressing
IP range 224.0.0.0 to 239.255.255.255 reserved for multicasting
Multicasting uses UDP
Hosts must choose to join a multicast group on a specific network interface
Routers send traffic to these hosts based on the routing information they have