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.