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CHAPTER 2 : NETWORK ACCESS - Coggle Diagram
CHAPTER 2 : NETWORK ACCESS
2.3.1 |
The Purpose Of ARP
Ethernet Protocol
MAC Sublayer
:check: There is 2 primary responsibility for the MAC sublayer which are Data Encapsulation and Media Access Control
:check: Data Encapsulation serves 3 main functions which is frame delimiting, addressing and error detection
:check: Media Access Control is responsible for the placement of frames on the media and removal of frames from the media and it communicates directly with the physical layer
Ethernet Encapsulation
:check: Ethernet is the most widely used LAN technology in the current era and is defined in the IEE 802.2 and 802.3 standards. Ethernet supports data bandwidth from 10 Mb/s until 100,000 Mb/s (100 Gb/s)
:check: Ethernet operates in the data link layer and the physical layer and also relies on the two sublayers of the data link in order to operate, the Logical Link Control (LLC) and the MAC sublayers
Ethernet Frame Fields
:check: Minimum Ethernet frame size from destination MAC address to FCS is 64 bytes up to 1518 butes
:check:
Collision Fragment
or
Run Frame
is the name for the frame that is less than 64 bytes and will be automatically discarded by the receiving stations
:check: Frames that is 1500 bytes or greater are considered
Jumbo
or
Baby Giant Frames
:check: The receiving device will drop the franes if it is either less or greter than the minimum and maximum amount of bytes
Address Resolution Protocol
ARP Functions
:check: An ethernet device will refer to an ARP table in its memory like the ram in order to find the MAC address that has been mapped to the IPv4 address
Example :
ARP Broadcast
:check: As a broadcast Frame, an ARP request qill be recieved and processed by every device on the local network. There is a possibility that multiple ARP request can flood the local segment if a large amount of devices were powered up and all start accessing network services at the same time
ARP Spoofing
:check: ARP spoofing is when an attacker pretends to be providers of services by responding to a request
:check: One method of ARP spoofing is when a attacker reply to a ARP request for the default gateway
Example :
Muhamad Abfis Shah
2.3.2 |
Explanation on why the IPv4 protocol requires other layers to provide reliability
IP - connectionless (
Afifah
)
:check: IP is a connectionless protocol:
No dedicated end-to-end connection is crested before data is sent.
very similar process as sending someone a letter through snail mail.
sender do not know whether or not the destination is present, reachable, or functional.
Characteristics of IP (
Afifah
)
:check: IP was designed as a protocol with low overhead- it provides only the function required to deliver a packet from the source to a destination.
:check: An IP packet is sent to the destination without prior establishment of a connection.
Encapsulating IP (
Afifah
)
:check: IP encapsulates the transport layer segment by adding an IP header for the purpose of delivery to the destination host.
:check: The IP header stays the same from the source to the destination host.
:check: The process of encapsulating data layer by layer enables the services at different layers to scale without affecting other layers.
IP - best effort delivery (
Afifah
)
:check: IP is considered "unreliable" because it does not guarantee that all packets that are sent will be received.
:check: Unreliable means that IP does not have the capability to manage and recover from undelivered, corrupt or out of sequence packets.
Network layer protocols (
Afifah
)
:check: There are several network layer protocols in existence; however, the most commonly implemented are:
Internet Protocol version 4 (IPv4)
Internet Protocol version 6 (IPv6)
IP - media independent (
Afifah
)
:check: from the media that carries the data at lower layers of the protocol stack- it does not care if the media is copper cables, fiber optics or wireless.
:check: The OSI data link layer is responsible for taking the IP packet and preparing it for transmission over the communications medium.
:check: The network layer does have a maximum size of the PDU that can be transported- referred to as MTU (maximum transmision unit)
The network layer (
Afifah
)
:check: The network layer uses 4 processes in order to provide end-to-end transport:
Addressing of end devices - IP adresses must be unique for identification purposes
Encapsulation - The protocol data units from the transport layer are encapsulated by adding IP header information including source and destination IP addresses.
Routing - The network layer provides services to direct packets to other network.
De-encapsulation - The destination host de-encapsulates the packet to see if it matches its own.
IPv4 packet header (
Khairi
)
An IPv4 header is a prefix to an IP packet that contains information about the IP version, length of the packet, source and destination IP addresses, etc. It consists of the following fields
For IPv4, this field has a value of 4
Limitations of IPv4 (
Khairi
)
IP address depletion
– IPv4 has a limited number of unique public IPv4 addresses available.
Internet routing table
A routing table contains the routes to different networks in order to make the best path determination
Lack of end-to-end connectivity
Network Address Translation (NAT) was created for devices to share a single IPv4 address
Introducing IPv6 (
Khairi
)
In the early ‘90s,the IETF started looking at a replacement for IPv4 – which led to IPv6 and it is designed to address the depletion of IP addresses and change the way traffic is managed
This thing provides an introduction to Internet Control Message Protocol (ICMP) and describes the functions of ICMP in an IPv6 network.
Encapsulating IPv6 (
Khairi
)
The IPv6 header is simpler than the IPv4 header,
example Between IPv6 and IPv4
Encapsulating IPv6 (cont.) (
Khairi
)
Advantages of IPv6 over IPv4 using the simplified header:
Simplified header format for efficient packet handling
Hierarchical network architecture for routing efficiency
Autoconfiguration for addresses
Elimination of need for network address translation (NAT) between private and public addresses
IPv6 packet header (
Khairi
)
IPv6 packet header fields:
Flow Label – 20-bit field suggests that all packets with the same flow label receive the same type of handling by routers
Payload Length – 16-bit field indicates the length of the data portion or payload of the packet.
Traffic Class – 8-bit field equivalent to the IPv4 Differentiated Services (DS) field
Next Header – 8-bit field is equivalent to the IPv4 Protocol field. It indicates the data payload type that the packet is carrying
Version – Contains a 4-bit binary value set to 0110 that identifies it as a IPv6 packet
IPv6 packet header (cont.)(
Khairi
)
IPv6 packet header fields:
Hop Limit – 8-bit field replaces the IPv4 TTL field.This value is decremented by 1 as it passes through each router. When it reaches zero, the packet is discarded
Source IPv6 Address – 128- bit field that identifies the IPv6 address of the sending host
Destination IPv6 Address – 128-bit field that identifies the IPv6 address of the receiving host
Khairi & Afifah
2.3.3 |
Explain how network devices use routing tables to direct packets to a destination network
IPv4 ROUTER ROUTING TABLE
(
Grace
)
Cisco IOS, show ip route
Display the router's IPv4 routing table
Directly connected and remote routes
How each route was learned
Trustworthiness and rating of the route
When the route was last updated
Which interface is used to reach the destination
Examines incoming packet's header to determine the destination either it matches or not and forward using the specified information in the routing table
DIRECTLY CONNECTED ROUTING TABLE ENTRIES (
Grace
)
Two of the routing table entries and created when a router interface is configured and activated
C
- Identifies the network directly connected and the interface is configured with an IP address and activated
L
- Identifies that it is a local interface and this is the IPv4 address of the interface on the router
DEFAULT GATEWAY (
Scarlet
)
:yellow_heart:Network device that can route traffic out to other networks.
:yellow_heart:This occurs when the destination host is not on the same local network as the sending host.
:yellow_heart:Know where to send the the packet using its routing table.
:yellow_heart:The sending host
doesn't need to know where to send the packet other than to the default gateway/router
UNDERSTANDING REMOTE ROUTE ENTRIES
(
Grace
)
D
- Identifies how the network was learned by the router
10.1.1.0/24
- Identifies the destination network
90
- Identifies the administrative distance (trustworthiness) of the route source
2170112
- Identifies the metric to reach the remote network
209.165.200.226
- Identifies the next-hop IP address to reach the remote control
00:00:05
- Identifies the amount of elapsed time since the network was discovered
Serial0/0/0
- Identifies the outgoing interface on the router to reach the destination network
HOST ROUTING TABLES
(
Scarlet
)
On a Windows host,you can display the routing table using :
:point_right::skin-tone-3:Route Print
:point_right::skin-tone-3:Netstat-r
3 sections will be displayed:
:heavy_check_mark:Interface List
:heavy_check_mark:IPv4 Route Table
:heavy_check_mark:IPv6 Route Table
HOST FORWARDING DECISION (
Scarlet
)
An important role of the network layer is to direct packets between hosts. A host can send a packet to
:bulb:
ITSELF
-A host can ping itself for testing purposes using
127.0.0.1 which is referred to as the loopback interface.
:bulb:
LOCAL HOST
-This is a host on the same local network as the sending host. The host
share the same network address
.
:bulb:
REMOTE HOST
-This is a host on a remote network. The host
do not share the same network address
.
USING THE DEFAULT GATEWAY
(
Scarlet
)
:writing_hand::skin-tone-3: A host's routing table usually includes a default gateway address-the router IP address for the network that the host is on.
:writing_hand::skin-tone-3:The host receives the IPv4 address for the default gateway from DHCP/it is manually configured.
:writing_hand::skin-tone-3:Having a default gateway configured creates a default route in the routing table of a host.
NEXT-HOP ADDRESS
(
Grace
)
Next-hop is an IP address entry in a router's routing table, which specifies the next closest/most optimal router in its routing path. Every single router maintains its routing table with a next hop address, which is calculated based on the routing protocol used and its associated metric.
ROUTER PACKET FORWARDING DECISION
(
Scarlet
)
When a router receives a packet destined for a remote network,the router has to look at its routing table to determine where to forward the packet. A router's routing table contains:
:cherries::Directly-connected routes
:cherries::Remote routes
:cherries::Default note
Scarlet & Grace
