14579932
Description
Flashcards by Matthew Swart, updated more than 1 year ago
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Created by Matthew Swart
almost 6 years ago
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| Question | Answer |
| Give an overview of internet organisations? | In 1992 the Internet Society (ISOC) was founded, with a mission to "assure the open development, evolution and use of the Internet for the benefit of all people throughout the world. The Internet Engineering Task Force (IETF) was formed during 1986 by the U.S. government to develop and promote Internet standards. Technical specification are published as RFCs. The IETF is overseen by the Internet Engineering Steering Group (IESG), and longer-term research is carried on by the Internet Research Task Force and overseen by the Internet Research Steering Group. IANA functions outsourced ICANN, a private non for profit company interview with IETF Chair Jari Arkko March 2014 |
| Who allocates IP Addresses? | The IANA's role is to allocate IP addresses from the pools of unallocated addresses to the Regional Internet Registry (RIRs), according to their needs as described by global policy and to document protocol assignments made by the IETF. When an RIR requires more IP addresses for allocation or assignment within its region, the IANA makes an additional allocation to the RIR. IANA does not make allocations directly to ISPs or end users except in specific circumstances, such as allocations of multicast addresses or other protocol specific needs. Users are assigned IP addresses by Internet service providers (ISPs). ISPs obtain allocations of IP addresses from a : local Internet registry (LIR) or National Internet Registry (NIR), or from their appropriate Regional Internet Registry (RIR) |
| IPv4 | IPv4 was initially deployed on 1 January 1983 and is still the most commonly used version. IPv4 addresses are 32-bit numbers often expressed as 4 octets in “dotted decimal” notation. IPv4 addresses contain 4 octets, each octet has a decimal value between 0 and 255. Each octet contains 8 bits. IPv4 addresses can also be displayed as a 32bit binary form, where the address is represented in a string of 1’s & 0’s. Each octet contains 8 bits. Each bit represents a value. (e.g. the 1st bit = 128) Bits are activated by changing their state from 0 to 1. The sum of the bits MUST equal the decimal value. The example below converts the 1st octet (168) to binary. |
| IPv6 | Deployment of the IPv6 protocol began in 1999. IPv6 addresses are 128-bit numbers and are conventionally expressed using hexadecimal strings. |
| IP Addressing | Each Network is assigned a network address & every device or interface (such as a router port) on the network is assigned a host address. |
| IPv4 Classes | In the early days of the Internet, the IANA (Internet Assigned Numbers Authority) defined five classes of public IP addresses. |
| IPv4 Classes cont. | The 32 bits of the IPv4 class address are divided into Network & Host portions, with the octets assigned as a part of one or the other. |
| Class A Addressing | Class A IP addresses use the 1st 8 bits (1st Octet) to designate the Network address. The 1st bit which is always a 0, is used to indicate the address as a Class A address & the remaining 7 bits are used to designate the Network. The other 3 octets contain the Host address. There are 128 Class A Network Addresses, but because addresses with all zeros (00000000) aren’t used & address 127(01111111) is a special purpose address, Indicates --126 Class A Networks are available. There are 16,777,214 Host addresses available in a Class A address. Rather than remembering this number exactly, you can use the following formula to compute the number of Hosts available in any of the class addresses, where “n” represents the number of bits in the Host portion: (2n – 2) = Number of available hosts. First number (00000000) is reserved for network number and the last (01111111) for broadcast address |
| Class B Addressing | Class B addresses use the 1st 16 bits (two octets) for the Network address. The last 2 octets are used for the Host address. The 1st 2 bit, which are always 10, designate the address as a Class B address & the remaining 14 bits are used to designate the Network. This leaves 16 bits (two octets) to designate the Hosts. Using our formula, (214 – 2), there can be 16,382 Class B Networks & each Network can have (216 – 2) Hosts, or 65,534 Hosts. |
| Class C Addressing | Class C addresses use the 1st 24 bits (three octets) for the Network address & only the last octet for Host addresses. The 1st 3 bits of all class C addresses are set to 110, leaving 21 bits for the network address, which means there can be: 2,097,150 (221 – 2) Class C Networks, but only 254 (28 – 2) Hosts per Network. |
| Classful Addressing | |
| Classful Network Architecture Summary | |
| IPv4 addresses - Classless | However the requirement that the network portion of address be exactly 1, 2 or 3 bytes turned out to be problematic for rapidly growing numbers of organisation with small and medium size networks. Class C with 254 hosts too small for many organisations however class B with potential for 65,534 too large. 1993 IETF standardized on Classless Interdomain Routing (CIDR) RFC 1519. With CIDR address, network part could be any number of bits long . CIDR address has the dotted decimal form a.b.c.d/x where x indicates the number of bits constitute the network portion of the address.Example a.b.c.d/21 the first 21 bits specify the network part of the address. The remaining 11 bits identify the specific Hosts on the network … the network address part of the IP is the same for all hosts on that network. |
| Subnets & Subnet Masks | With the rapid growth of the internet & the ever-increasing demand for new addresses, the standard address class structure has been expanded by borrowing bits from the Host portion to allow for more Networks. Under this addressing scheme, called Subnetting, separating the Network & Host requires a special process called Subnet Masking. The subnet masking process was developed to identify & extract the Network part of the address. A subnet mask, which contains a binary bit pattern of ones & zeros, is applied to an address to determine whether the address is on the local Network. If the address is not, then the process of routing it to an outside network begins. The function of a subnet mask is to determine whether an IP address exists on the local network or whether it must be routed outside the local network. It is applied to a message’s destination address to extract the network address. If the extracted network address matches the local network ID, the destination is located on the local network. However, if they don’t match, the message must be routed outside the local network. |
| Subnets & Subnet Masks Cont. | Network address is identified by Logical AND of IP address and Subnet mask. The only way you can get a result of a 1 is to combine 1 & 1. Everything else will end up as a 0. The subnet mask is like a filter that is applied to a message’s destination IP address. Its objective is to determine if the local network is the destination network. |
| IPv4 Private address space | IANA has reserved the following 3 blocks of IP address space for Private internet. The same private addresses can be used by many enterprises, they can be used to communicate within the private network only. Private addresses cannot be used to communicate outside the private network. Hosts with private address must communicate to public network via router/gateway. |
| IPv4 Private address space cont. | |
| Network Address Translator (NAT) | NAT allows devices (routers) to intermediate between private and public networks by translating an unregistered IP address into a registered IP address. NAT enabled router appears to external network as one device with one IP address. NAT enable router is hiding details of the private network from external network (internet). |
| Port based NAT | |
| Dynamic allocation of IP address for newly connect network host | Dynamic Host Configuration Protocol (DHCP). Client server protocol Automatic allocation of IP addresses to connected hosts. Temporary IP assignment. Static allocation of IP addresses. MAC based host address allocation |
| Dynamic Host Configuration Protocol (DHCP) |
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