Week 2 Flashcards
Dynamic host configuration protocol
The protocol involved with handing out dynamic IP addresses to devices within a network
When are static IP addresses usually given?
To servers and network devices
IP datagram
A highly structured series of fields that are strictly defined
The two primary sections of an IP datagram are the header and the payload
Version field
First field of the IP datagram that is 4 bytes long and it states what version IP address the datagram uses (IPv4 or IPv6)
Header Length field
Almost always 20 bytes in length when dealing with IPv4
Service type field
8 bits long and can be used to specify details about quality of service (QoS) technologies
Total length field
A 16 bit field used to declare how long the attached IP datagram is
Identification field
A 16 bit number used to group messages together : if a very large datagram needs to be sent then it will be split into multiple datagrams and the identification field will be the same for each of those datagrams so the recipient router knows the segments are connected
How large can a single datagram be?
The largest number that can be represented with 16 bits: 65,535
Flag field
Used to indicate if a datagram is allowed to be fragmented, or to indicate that the datagram has already been fragmented
Fragmentation
The process of taking a single IP datagram and splitting it up into several smaller datagrams
Time to live (TTL) field
An 8 bit field that indicates how many router hops a datagram can traverse before it’s thrown away
Protocol field
Another 8 bit field that contains data about what transport layer protocol is being used
Header checksum field
A checksum of the contents of the entire IP datagram header: changes at every router it goes through along with the TTL field
IP options field
An optional field and is used to set special characteristics for datagrams primarily used for testing purposes : usually followed by a padding field
Padding field
A series of zeroes used to ensure the header is the correct total size
Address class system
A way of defining how the global IP address space is split up
Class A IP addresses
The first octet is used for the network ID and the last three are for the host ID
Class B IP addresses
The first two octets are for the network ID and the remaining two are for the host ID
Class C IP addresses
The first three octets are for the network ID and the last one is for the host ID
CIDR
Classless Inter-Domain Routing
Address Resolution Protocol (ARP)
A protocol used to discover the hardware address of a node with a certain IP address
ARP Table
A list of IP addresses and the MAC addresses associated with them : generally expire quickly to account for network changes
Subnetting
The process of taking a large network and splitting it up into many individual and smaller subnetworks , or subnets
Subnet masks
A way for a computer to use AND operators to determine if an IP address exists on the same network
Demarcation point
To describe where one network or system ends and another one begins
Router
A network device that forwards traffic depending on the destination address of that traffic.
What are the four basic steps a router takes to send data?
- Receives data packet
- Examines destination IP
- Looks up IP destination network in routing table
- Forwards traffic to destination
What are the two sub categories of interior gateway protocols?
Link state routing protocols
Distance-vector protocols
Interior gateway protocols
Used by routers to share information within a single autonomous system
Autonomous system
A collection of networks that all fall under the control of a single network operator
Internet Assigned Numbers Authority (IANA)
A nonprofit organization that helps manage things like IP address allocation and autonomous system allocation
Why is the autonomous system number (ASN) only represented by one decimal number?
Because it never changes and, unlike IP addresses, it does not represent multiple ID’s within the same number like IP addresses do for host ID and network ID
People also don’t really look at ASN’s so it’s not necessary to be as readable
