35 Questions
What is the function of the input buffer in decentralized switching?
Queue datagrams until they can be forwarded into the switch fabric
In decentralized switching, how is the output port determined using the forwarding table?
Using header field values and a forwarding table in the input port memory
What is the purpose of longest prefix matching in forwarding table lookup?
To use the longest address prefix that matches the destination address
What is the main function of switching fabrics in a network?
Transfer packets from input buffer to appropriate output buffer
How is the switching rate typically measured in a network?
As a multiple of input/output line rate
What is the role of generalized forwarding in decentralized switching?
Forward based on any set of header field values
In decentralized switching, how are ranges for forwarding table entries handled if they don't divide up neatly?
Use longest prefix matching for accurate lookup
What happens if datagrams arrive faster than the forwarding rate into the switch fabric in decentralized switching?
They are queued in the input buffer until they can be forwarded
What determines the output port in destination-based forwarding?
Destination IP address
What does Ethernet link layer protocol perform during lookup and forwarding in input ports?
Lookup and forwarding using header field values
What is the function of the routing control plane in a router?
Determine the route taken by packets from source to destination
Which component determines how datagrams arriving on a router's input port are forwarded to the router's output port?
Forwarding: move packets from router's input to appropriate router output using data plan
What is the difference between data plane and control plane in network routing?
Data plane operates in nanosecond timeframe, while control plane operates in millisecond timeframe
What is the purpose of the network layer protocols in every host and router?
Encapsulate segments into datagrams on the sending side and delivers segments to the transport layer on the receiving side
What is the function of the forwarding component in a router?
Move packets from router's input to appropriate router output using data plan
What are the two approaches for the control plane in terms of routing algorithm?
Per-router control plane and centralized control plane
What is the primary function of the network layer protocols in every host and router?
Encapsulate segments into datagrams on the sending side and delivers segments to the transport layer on the receiving side
What is the function of the routing processor in a generic router architecture?
Determines route taken by packets from source to destination using control plan
What is the role of individual routing algorithm components in each and every router in terms of the control plane?
Determines route taken by packets from source to destination using control plan
What is the primary responsibility of the data link layer?
Transferring datagram from one node to a physically adjacent node over a link
How does the data link layer handle the data stream received from the physical layer?
Assembles them into a recognizable frame format
What is the main function of the data link layer protocols and sub-layers?
Error detection and correction
What is the role of the data link layer in terms of framing?
Encapsulating packets from the network layer into frames
In what form does the data link layer pick up data from hardware at the adjacent node?
Electrical signals
How is datagram transferred by different link protocols over different links?
Using different protocols such as Ethernet and 802.11
What is the main function of the Logical Link Control (LLC) sublayer in the data link layer?
Dealing with framing and error detection
What type of error involves a change of only one bit in a data unit?
Single-bit Error
Which mechanism is the most common and least expensive for error detection in data units?
Simple Parity Checking
What is the primary responsibility of the Media Access Control (MAC) sublayer in the data link layer?
Providing hardware addressing mechanism
In which type of error do two or more bits in the data unit change from 0 to 1 or vice-versa?
Burst Error
What is the improvement achieved by using two-dimensional parity check compared to a simple parity check?
Increased error detection capabilities
Which error detection mechanism organizes the block of bits in the form of a table to improve performance?
Two-dimensions Parity Check
What is the responsibility of the Data Link layer in terms of addressing?
Providing hardware addressing mechanism
Which sub-layer of the Data Link layer deals with controlling physical media access?
Media Access Control (MAC)
What does Cyclic Redundancy Check (CRC) provide in addition to error detection?
Both error detection and correction
Study Notes
Decentralized Switching
- The input buffer stores incoming datagrams before they are processed by the switching fabric.
- The output port is determined using the forwarding table, which is searched using longest prefix matching to find the best match.
- Generalized forwarding allows for more complex forwarding decisions to be made.
Switching Fabrics
- The switching rate is typically measured in packets per second.
- Switching fabrics are responsible for forwarding datagrams from input ports to output ports.
Forwarding Table Lookup
- Longest prefix matching is used to find the best match in the forwarding table.
- Ranges for forwarding table entries are handled by dividing them into smaller sub-ranges if they don't divide up neatly.
Datagrams and Forwarding Rate
- If datagrams arrive faster than the forwarding rate, they may be dropped or buffered.
- The output port is determined by the forwarding table in destination-based forwarding.
Router Components
- The routing control plane is responsible for determining how datagrams are forwarded through the router.
- The forwarding component determines how datagrams are sent to the output port.
- The routing processor executes the routing algorithm.
Control Plane and Data Plane
- The control plane is responsible for determining how datagrams are forwarded, while the data plane is responsible for forwarding them.
- The control plane can use either traditional routing algorithms or software-defined networking (SDN) architectures.
Network Layer Protocols
- Network layer protocols are responsible for routing and forwarding datagrams between hosts and routers.
- The primary function of network layer protocols is to provide logical communication between hosts and routers.
Data Link Layer
- The data link layer is responsible for providing error-free transfer of data frames between nodes on the same link.
- The primary responsibility of the data link layer is to provide framing, error detection and correction, and flow control.
- The data link layer picks up data from the physical layer as a stream of bits.
- The data link layer handles the data stream by breaking it into frames, detecting and correcting errors, and controlling flow.
Error Detection and Correction
- A single-bit error involves a change of only one bit in a data unit.
- A multi-bit error involves a change of two or more bits in a data unit.
- The most common and least expensive error detection mechanism is the parity check.
- Cyclic Redundancy Check (CRC) provides error detection and correction.
- Two-dimensional parity check improves performance by detecting errors more efficiently.
Media Access Control (MAC) Sublayer
- The MAC sublayer is responsible for controlling access to the physical media.
- The MAC sublayer provides addressing and error detection and correction.
This quiz covers the content from Lecture 9 of Computer Networks by Dr. Dina Fawzy, focusing on the transport segment from sending to receiving host, encapsulating segments into datagrams, and the network layer protocols in every host and router.
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