The Bits and Bytes of Computer Networking Module 2
Protocol
8-bit field that contains data about what transport layer protocol is being used.
IP Datagram
Highly structured series of fields that are strictly defined.
Flag
Indicate if datagram is allowed to be fragmented or if already fragmented.
Types of routing protocols
Interior and exterior gateway protocols
IANA
Internet Assigned Numbers Authority
Total hops
Keeps track of how far away that destination currently is. It has information about best path to send information.
Types of Interior Gateway Protocols
Link state routing and distance vector protocol.
ARP Table
List of IP addresses and the MAC addresses associated with them. They expire after a short amount of time to account for new ones.
IP address belong to...
networks. For example, home and cafe is different.
MAC Address belong to...
specific devices attached to the network.
TTL purpose
8-bit field that indicates how many routers hops a datagram can traverse before it's thrown away. So, there is no endless loop trying to find its destination.
Distance-Vector vs Link State
- Distance is slower to react - Link requires more memory and processing power
Destination Network
Has a row for each network it is familiar with, network ID and net mask.
ARP purpose
Protocol used to discover hardware address of a node with a certain IP address.
Basic Routing
1. Receive data packet 2. Examines destination IP 3. Looks up IP destination network in routing table 4. Forwards traffic to destination
Three Main Ranges of Non-Routable Address Space
10.0.0.0/8 172.16.0.0/12 192.168.0.0/16
Total Length
16 bits. Indicates total length of the IP datagram.
Identification
16-bit number used to group messages together.
Host ID Octet Location
2-4. For example, 100.100.100 in this IP address 9.100.100.100.
Service Type
8 bits. Specify details about quality of service and technologies.
Dotted Decimal Notation
255.255.255.255
8 bits is how many addresses?
2^8 = 256
Subnet mask
32-bit numbers that are normally written out as four octets in decimal. For example, 255.255.254.0. The 254 when in binary is 1111.1111.1110.0000 - All zeros are host, and all ones are network.
Header Length
4 bits. How long the entire header is.
Version
4 bits. Indicates what version of IP is being used.
Turn IP address - 9.100.100.100 with subnet mask 255.255.255.0 into CIDR notation.
9.100.100.100/24 because there are 24 ones when subnet mask is converted to binary.
CIDR Notation
A shorthand method for denoting the distinction between network and host bits in an IP address.
ARP
Address Resolution Protocol
ARP Response
After an ARP message, this occurs to tell the sender the IP address.
ASN
Autonomous System Number
Header Checksum
Check for any errors, similar to ethernet frame checksum.
Types of IPv4 Address Classes
Class A, B, C
CIDR
Classless Inter-Domain Routing
CIFR
Classless Inter-Domain Routing
Autonomous system
Collection of networks that all fall under the control of a single network operator
Routing Table
Commonly contains destination network, Next hop, Total hops, interface
Fragmentation Field
Contains values by receiving end to put the fragmented packets back together.
Demarcation Point
Describe where one network or system ends and another begins.
DHCP
Dynamic Host Configuration Protocol
Link State Routing Protocol
Every router knows every detail about every other router in the system.
Network ID Octet Location
First. For example, 9 in this IP address 9.100.100.100.
Dynamic IP
IP address automatically assigned by DHCP server.
Static IP
IP address manually inputted.
Next hop
IP address of next router that should receive data for the destination network or state the network is directly connected.
Class B
Network (16 bits) = first two octet Host (16 bits) = last two octet 10xx 128-191
Class C
Network (24 bits) = first three octet Host (8 bits) = last octet 110x 192-223
Class A
Network (8 bits) = first octet Host (24 bits) = rest 0xxx 0-127
NAT
Network Address Translation
Router
Network device that forwards traffic depending on the destination address of that traffic.
What is the IANA?
Nonprofit organization that helps manage things like IP address allocation, and ASN.
ASN purpose
Numbers assigned to individual autonomous systems. 32-bit numbers.
Subnetting
Process of taking a large network and splitting it up into many smaller subnetworks.
Fragmentation
Process of taking a single IP datagram (Max size of 16) and splitting it up into several smaller datagrams
Non-Routable Address Space
Ranges of IPs set aside for use by anyone that cannot be routed to.
RFC
Request for Comments
Distance-Vector Protocol
Sends the entire routing table to its neighboring router and keeps track of total hops.
Padding
Series of zeros to ensure the header is the correct total size.
Demarcate
Set something off.
subnet ID
Single octet that uses up space from the host ID
Fields that are 32 bits long
Source and Destination IP Address
IP Address can be split into two...
called the network and host ID.
Types of IP datagram protocols
TCP, UDP
TTL
Time to Live
Interior Gateway Protocols
Used by routers to share information within a single shared autonomous system.
Exterior Gateway Protocols
Used to communicate data between routers representing the edges of an autonomous system.
IP Options
Used to set special characteristics for datagrams primarily used for testing purposes.
Routing Protocols
Used to speak to each other in order to share information they have
IP Datagram Structure
Version, Header Length, Service Type, Total Length, Identification, Flag, Fragment Offset, TTL, Protocol, Header Checksum, Source, Destination, Options, Padding
Address Class System
Way of defining how the global IP address space is split up
ARP Message
When there is no entry in the ARP table with an IP address, the device will send this as a broadcast to all devices on the local network.