CS2005 - Lecture 7 - Network Layer I Flashcards
(42 cards)
What are the two key functions of the network layer?
Forwarding: Move packets from input link to output link at a router; Routing: Determine the path that packets take from source to destination
What is the difference between the control plane and the data plane in the network layer?
Control plane: Determines end-to-end paths through the network (routing algorithms); Data plane: Per-router operations that move packets from input to output ports
In the network layer, what happens on the sending side?
Segments are taken from the transport layer; Each segment is encapsulated into a datagram; Datagrams are sent to a nearby router
What is the role of the network layer on the receiving side?
Receives datagrams from the router; Extracts transport layer segments; Delivers segments to the transport layer
Define Forwarding.
Router-local action transferring a packet from an input link to the correct output link
Define Routing.
Network-wide action determining the end-to-end paths for packets
How is a packet forwarded within a router?
The router examines packet header fields; Uses header values to index into the forwarding table; Forwards the packet to the output interface indicated
What is the traditional approach for configuring a router’s forwarding table?
Routing algorithms run on each router; Routers exchange routing messages and compute their own forwarding tables
How does the SDN (Software Defined Networking) approach differ?
Routing is centralized in a remote controller; Controller computes and distributes forwarding tables to routers; Routers only perform forwarding
List the four components of a router.
Input ports; Switching fabric; Output ports; Routing processor
What functions are performed by an input port in a router?
Terminate incoming physical link; Perform link-layer functions; Lookup and determine output port; Forward control packets to routing processor
What is the role of a routing processor in traditional routers?
Execute routing protocols; Maintain routing tables and link-state information; Compute the forwarding table
What is the goal of a routing algorithm?
Determine good paths (least cost, fastest, least congested) from sender to receiver
What is the cost of a path in a network graph?
Sum of the costs of all individual links along the path
Name types of routing algorithms based on network knowledge.
Centralized: Each router has complete network information; Decentralized: Each router knows only its neighbors
What is the difference between static and dynamic routing?
Static: Routes change slowly over time; Dynamic: Routes update frequently with changes in network traffic or topology
What does the first diagram represent overall?
The layered architecture (Application, Transport, Network, Data Link, Physical) across different devices and network components
In Diagram 1, which layers are present at routers?
Network, Data Link, and Physical layers
Which devices in diagram 1 implement the Application and Transport layers?
End hosts (laptops, servers, smartphones) implement the Application and Transport layers
What is missing from the routers compared to end hosts in diagram 1?
Routers do not implement Application or Transport layers
How is communication established between end systems according to the layer model shown in Diagram 1?
End systems use all layers; routers forward based on the Network layer information
What role does the data link layer play at routers in the diagram 1?
Ensures correct data transfer between neighboring routers or devices
In diagram 1, which layer ensures the physical transmission of bits?
The Physical layer
What does the second diagram illustrate?
It shows how a router uses the local forwarding table to forward packets based on header values
