week 5 Flashcards
what are the 4 processes that the network layer provides
- -> addressing end devices
- -> encapsulation
- -> de encapsulation
- -> routing
what is addressing end devices
end devices must have unique IP addresses for identification on the network
what is encapsulation and de encapsulation
–> encapsulation is the process where the network layer adds network header information, such as the IP address of the source and destination hosts, to the protocol data unit from the transport layer to form a packet.
–> routers only consider the contents fo the packet header that encapsulated the segment for routing
–> De-encapsulation is when the packet arrives at the destination host, it removes the IP header by de-encapsulation and hands the resulting Layer 4PDU to the appropriate service at the transport layer
What is routing
–> The network layer provides services to direct packets to their destination hosts on other networks using routers
what are the 2 common network layer protocols
IPV4
IPV6
what are the legacy network layer protocols
Novell internetwork packet exchange (IPX)
Apple Talk
connectionless network service
what are the characteristics of IP addresses
connectionless
best effort (unreliable)
media independent
what does it mean when ip protocol is connectionless
- -> there is no dedicated end-to-end connection created before the data is sent
- -> connectionless communication is conceptually similar to sending a letter to someone without notifying the recipient in advance
- -> IP requires no initial exchange of control information to establish an end-to-end connection before the packets are forwarded
- -> senders are unaware of
- -> whether destination devices are present and functional when sending packets
- -> whether the destination receives the packet
- -> whether the destination is able to access and read the packet - -> the receiver does not know when the packer is coming
what does it mean when ip protocol is best effort delivery
- -> IP is unreliable or best effort delivery
- -> Unreliable simply means that IP has no capability to manage and recover from undelivered or corrupt packets
- -> IP does
- -> not inform sender whether the delivery was successful
- -> not track the order of packet delivery, packets can arrive out of order
- –> not provide acknowledgement of packet delivery
- -> no provide error control to track if packers were corrupted - -> IP is fast and efficient
- -> Requires Upper layer to resolve these issues
what does it mean when ip protocol is media independent
- -> IP operates independently of the media that carry the packets
- -> However, IP provides fragmentation to cater for different maximum transmission unit (MTU) for different media
- -> Different media has different maximum transmission unit (MTU), the maximum size of the PDU that each medium can transport
- -> The data link layer passes the MTU value of the media to the network layer
- -> Large packets are split up into smaller ones when forwarded from one medium to another medium with a smaller MTU by fragmentation
what are the IPV4 packet header field
version - identifies IP packet version
differentiated services - determines the priority of each packet
time to live - limit the lifetime of the packet (no of hops )
protocol - indicates the payload type (TCP, UDP, ICMP)
source IP address - 32-bit binary value that represents the source
destination IP address - 32-bit binary value that represents the destination
Internet header length - length of the header
total length - entire packet size
header checksum - error checking of IP header
identification - uniquely identify IP fragment
flags - reconstruct fragments into packet
fragment offset - helps identify the order to place the packet fragment
what are the limitations of IPv4
–>IPv4 address is depleting as IPv4 has a limited number of public IP addresses available
–> Internet routing table expansion - a routing table is used by routers to determine the best path to determinations. As the numbers of servers connected to the internet increases, so too does the number of network routes. These IPv4 routes consume a great deal of memory and processor resources on internet routers.
–> Lack of end-to-end connectivity - as there were limited IP addresses, network address translation, provides a way for multiple devices to share a single public IP address.This caused the lack of end-to-end connectivity
advantages of IPv6
–> increased address space - IPv6 addresses are 128 bit hierarchical addressing as opposed to IPv4 with 32 bits. IPv6 address space provides 340 undecillion addresses vs ipv4 which only provides 4 billion addresses
–> improved packet handling - the IPv6 header has been simplified with fewer fields which improves packet handling by intermediate routers.
–> Eliminated the need for nat - with a large no of public addresses, NAT is not needed, hence providing end to end connectivity
–> Integrated security - IPv6 natively supports authentication and privacy capabilities
what does the IPv6 packet header contain
version
traffic class - same as differentiated service for IPV4
flow label - maintains same path for packets so that they are not reordered
payload length - length of packet size
next header - payload type
hop limit - same as time to live
source address - 128 bit field
destination address - 128 bit field
