Bits and Bytes of Networking Week 2

Class A IP Address

1-126 Leading bits. 128 Networks. 16,777,214 Hosts per Network. Default Subnet Mask 255.0.0.0

Class B IP Address

128-191 Leading bits. 16,384 Networks. 65,534 Hosts per Network. Default Subnet Mask 255.255.0.0

Total Length

16 bit field indicates total length of IP Datagram it's attached to

Identification Field

16 bit number used to group messages together max size of a single datagram is the largest number you can represent w/16 bits 65,535. If total data is more than can fit in single datagram, IP layer splits data into individual packets. This field shows it's all the same transmission.

Class C IP Address

192-223 Used by small offices and home offices Subnet mask 255.255.255.0

Protocol Field

8 bit contains data about what transport layer protocol is being used TCP/UDP

Time to Live (TTL)

8 bit field indicates maximum amount of router hops a datagram cam traverse before being thrown away. Prevents datagrams from getting stuck in a loop

Subnet Mask

A 32-bit number that numerically describes the format of an IP address, by representing the combined network and subnet bits in the address with mask bit values of 1, and representing the host bits in the address with mask bit values of 0. (Ignores 1's, pay attention to 0's)

Single Autonomous System

A collection of networks that all fall under the control of a single network operator

ARP Table

A database of records that maps MAC addresses to IP addresses. The ARP table is stored on a computer's hard disk where it is used by the ARP utility to supply the MAC addresses of network nodes, given their IP addresses.

Request for Comments (RFC)

A document published by the IETF that details information about standardized Internet protocols and those in various development stages.

Autonomous System Number (ASN)

A globally unique number allocated for a collection of networked systems that operate common routing protocols and are under control of a single administrative authority a.k.a autonomous systems. 32 bit

Router

A network device that forwards data packets from one network to another. Must be connected to two networkds

Classless Interdomain Routing (CIDR) notation

A notation that is often used to represent an IP address and its subnet mask.

Interior Gateway Protocol (IGP)

A routing protocol that operates within an autonomous system, which is a network under a single administrative control. OSPF (Open Shortest Path First) and EIGRP are popular examples of them.

Distance Vector Protocol

A routing protocol that routers use to share information about an internetwork's status by copying their routing table to other routers with which they share a network.

Padding

A series of 0's used to ensure the header is the correct total size

Address Class System

A way of defining how global IP address space is split up

Quality of Service (QoS)

Allows routers to make decisions about which IP Datagram may be more important

Dynamic Host Configuration Protocol (DHCP)

Assigns dynamic Ip Addresses for clients

Exterior Gateway

Communicate data between routers representing edges of an autonomous system. i.e. Border Gateway Protocol (BGP)

Header Checksum

Cyclic redundancy check (CRC) on header only

Header Length Field

Declares length of the entire header almost always 20 bytes when IPv4 the minimum length of IP header.

Demarcation Point

Describes where one network or system ends and another begins

Link-state Protocol

Each router advertises the state of link to each of it's interfaces. Requires more memory and processing power common types OSPF (Open Shortest Path First)

Version

In header it's the first 4 bits that show the version protocol. Most common is IPv4

Flag Field

Indicate if a datagram is allowed to be fragmented or to indicate that the datagram has already been fragmented.

Non-routable address space

Interior gateway portocols will rout but exterior will not

IP Options Field

Optional field and is used to set special characteristics for datagram primarily used for testing purposes

Static IP

Reserved for servers and network devices

IP Datagram

The IP portion of a TCP/IP frame that acts as an envelope for data, holding information necessary for routers to transfer data between subnets.

Internet Assigned Numbers Authority (IANA)

The international organization responsible for allocation of IP addresses and Autonomous System Number(ASN). Part of the Internet Corporation for Assigned Names and Numbers (ICANN).

Routing Protocols

The means by which routers communicate with each other about network status. Routing protocols determine the best path for data to take between nodes.

Subnetting

The process of logically dividing a network into smaller subnetworks or subnets. They have their own gateway routers

Address Resolution Protocol (ARP)

Used to discover the hardware address of a node w/certain IP addresses

Fragmentation

is the process of taking a single a single IP datagram and splitting it into smaller datagrams