OSI Layer 3 Network Layer + Subnetting | Week 2 lecture + readings Flashcards
While the ____-____ layer is the software that solves the “how to send from me to nearby” problem, the _____ layer solves “how to send from me to far away.”
While the data-link layer (layer 2) is the software that solves the “how to send from me to nearby” problem, the network layer (layer 3) solves “how to send from me to far away.”
The network layer involves which protocol data unit?
packets(IP) and datagrams (UDP)
the data-link layer involves which protocol data unit?
frames
the physical layer involves which protocol data units?
bits
the transport layer involves which protocol data units?
TCP segments
layer-3 provides communication between networks. True or false?
true
What two major functions does the network layer perform?
Routing and forwarding.
At layer 3, how does routing function?
routing collects network topology into routing tables. It affects the way routers forward traffic.
Forwarding, a layer 3 activity, is what?
The process of handling incoming packets. It forwards packets to the next hop.
The network layer is concerned with what?
The network layer is concerned with point to point delivery.
What is a host?
An end system where traffic starts or finishes (usually)
What is a router?
An intermedia system which passes messages to another network.
____ communicate with other _____ to determine network topology and sometimes are the end points, but mostly are the things inbetween.
routers.
IP is global and unique, and because of this, it is used to provide and deliver what?
Provides: Universal addressing, routing of packets between hosts.
Delivers: Packets from source to destination. End-to-end, not link-to-link.
IP is an unreliable connectionless packet delivery service. True or false?
True
What does unreliable mean, with regards to IP being an unreliable connectionless packet delivery service?
Delivery not guaranteed.
Best effort to attempt to deliver a packet.
Packets may be lost, corrupted, delayed or duplicated.
Acknowledgement of receipt is not required.
Sender/receiver not informed when a packet is lost, etc.
Acknowledgement of packets is a responsibility of higher layer transport protocols such as TCP.
What does connectionless mean, with regards to IP being an unreliable connectionless packet delivery service?
Order is unimportant to IP.
Every packet is treated as its own message.
No ordering relationship between consecutive packets.
Packets are just transmitted individually.
If order is important, this becomes the transport layer’s responsibility (layer 4).
What is IP’s simple failure model?
Packets can be lost, corrupted, delayed, or duplicated. However, simple failure means all errors are treated as packet loss.
What are the network layer functions?
Addressing, routing, and forwarding.
Who manages IP addresses?
ICANN Internet Corporation for Assigned Names and Numbers, who manages some domains directly and authorises some companies to become domain name registrars as well.
What provides a dynamic IP address?
Dynamic Host Control Protocol.
The ___ and ____ layers are responsible for moving messages from end to end in a network.
The network and transport layers are responsible for moving messages from end to end in a network.
What 3 functions does the transport layer (layer 4) perform?
The transport layer (layer 4) performs 3 functions
1. linking the application layer to the network,
2. segmenting
and session management (establishing end to end connection between sender and reciever)
What two functions does the network layer perform?
The network layer (layer 3) performs two functions: routing and addressing. Routing is determining the next computer to which the message should be sent to reach the final destination. Addressing is finding the address of that next computer.
