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Questions and Answers
Which of the following best describes packet switching?
In queuing delay, packets can be dropped if the memory buffer is full.
True
What two key functions are performed in the network core?
Routing and forwarding
The _____ is responsible for determining the route packets take from source to destination.
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Match the following concepts with their descriptions:
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What is primarily responsible for connecting end systems to an edge router?
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The core of the Internet consists of isolated networks with no routers.
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What are the two main types of hosts in a network?
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The _______ network provides a connection to a national or global ISP.
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Match the following terms with their descriptions:
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Study Notes
Network Core
- The network core is made up of interconnected routers.
- Packet-switching: Host computers break application-layer messages into packets.
- Each packet is forwarded from one router to the next across links along the path from source to destination.
- Packets are transmitted at the full link capacity.
- With store-and-forward packet switching, the entire packet must arrive at a router before it can be transmitted on the next link.
- Queueing delay: Occurs when the packet arrival rate on a link exceeds the transmission rate.
- Packets queue up, waiting to be transmitted on the link.
- Packet loss can occur if the memory (buffer) for the queue fills up.
Routing and Forwarding
- Routing: Determines the source-destination route taken by packets.
- Forwarding: Moves packets from a router's input to the appropriate router output.
- A routing algorithm determines a local forwarding table which stores information about the output link for each destination address.
Circuit Switching
- Circuit switching is an alternative core network model.
- Resources are allocated and reserved for a "call" between the source and destination.
- This is in contrast to packet-switching where there is no pre-allocation of resources.
Internet Structure
- The internet structure is made up of three key components:
- Network edge: Hosts (clients and servers) connected to data centers.
- Access Networks: Wired and wireless networks used to connect hosts to the edge router.
- Network core: Interconnected routers forming a network of networks.
Access Networks and Physical Media
- Access Networks connect end systems to the edge router.
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Physical media used for access networks include:
- Wired (e.g., Ethernet cable, fiber optic cable)
- Wireless (e.g., Wi-Fi)
Delays in Network Communication
- Transmission Delay: Time required to push all of a packet's bits into the link.
- Propagation Delay: Time for the first bit of a packet to travel from the beginning of the link to the destination router. This depends on the physical medium and the distance traveled.
- Queueing Delay: Delay experienced by packets waiting in a queue to be transmitted on a link. It depends on the average packet arrival rate and the link bandwidth.
Measuring Delays and Routes
- The traceroute program can measure delays between the sender and routers along a network path to a destination.
- It sends three packets to each router and times the interval between transmission and reply.
- The results provide insights into the delays and the route taken by packets.
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Description
Explore the complex world of network architecture with this quiz focusing on the network core and the essential concepts of routing and forwarding. Test your understanding of packet-switching, queueing delays, and the role of routing algorithms in directing packets from source to destination.
