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Questions and Answers
Switching via memory is faster than switching via a bus.
Switching via memory is faster than switching via a bus.
True
The Cisco 12000 switches 60 Gbps through the interconnection network crossbar.
The Cisco 12000 switches 60 Gbps through the interconnection network crossbar.
False
Link layer protocol is responsible for line termination.
Link layer protocol is responsible for line termination.
False
Routers use distance vector routing algorithms in the Internet.
Routers use distance vector routing algorithms in the Internet.
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IP datagram format includes information about the number of hops remaining for the packet.
IP datagram format includes information about the number of hops remaining for the packet.
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Priority scheduling in network neutrality ensures fair performance for all datagrams.
Priority scheduling in network neutrality ensures fair performance for all datagrams.
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In router architecture, the forwarding table is pushed to output ports for routing.
In router architecture, the forwarding table is pushed to output ports for routing.
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Decentralized switching involves looking up the output port using the forwarding table in the output port memory.
Decentralized switching involves looking up the output port using the forwarding table in the output port memory.
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Memory switching in first-generation routers involves the CPU controlling the switching directly.
Memory switching in first-generation routers involves the CPU controlling the switching directly.
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Switching via a bus is limited by bus bandwidth due to potential bus contention.
Switching via a bus is limited by bus bandwidth due to potential bus contention.
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Interconnection networks like banyan networks were initially developed for single-processor systems.
Interconnection networks like banyan networks were initially developed for single-processor systems.
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In switching via an interconnection network, datagrams are fragmented into variable length cells.
In switching via an interconnection network, datagrams are fragmented into variable length cells.
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A routing algorithm determines the local forwarding at a router.
A routing algorithm determines the local forwarding at a router.
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Connection setup is the least important function in some network architectures.
Connection setup is the least important function in some network architectures.
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In a datagram network, routers have state about end-to-end connections.
In a datagram network, routers have state about end-to-end connections.
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The network layer is responsible for connection services between two processes.
The network layer is responsible for connection services between two processes.
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Hierarchical routing is a type of routing algorithm used in the Internet.
Hierarchical routing is a type of routing algorithm used in the Internet.
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Routers establish virtual connections before datagrams flow in some network architectures.
Routers establish virtual connections before datagrams flow in some network architectures.
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Study Notes
Router Architecture and Functions
- Two key router functions: running routing algorithms/protocols and forwarding datagrams from incoming to outgoing links
- Forwarding tables are computed and pushed to input ports, routing processor handles routing, management, and control plane (software), and forwarding data plane (hardware)
Input Port Functions
- Link layer protocol (receive) and line termination
- Lookup and forwarding, switch fabric, and queueing
- Physical layer handles bit-level reception, and data link layer handles e.g., Ethernet (see Chapter 5)
Switching Fabrics
- Transfer packet from input buffer to appropriate output buffer
- Switching rate is the rate at which packets can be transferred from inputs to outputs
- Three types of switching fabrics: memory, memory bus, and crossbar
Switching via Memory
- First-generation routers used traditional computers with switching under direct control of CPU
- Packet copied to system's memory, speed limited by memory bandwidth (2 bus crossings per datagram)
Switching via a Bus
- Datagram from input port memory to output port memory via a shared bus
- Bus contention limits switching speed, e.g., 32 Gbps bus in Cisco 5600
Switching via Interconnection Network
- Overcome bus bandwidth limitations using banyan networks, crossbar, or other interconnection nets
- Fragmenting datagram into fixed-length cells, switching cells through the fabric
Interplay between Routing and Forwarding
- Routing algorithm determines end-end-path through network
- Local forwarding table determines local forwarding at this router based on header value and output link
IP Datagram Format
- IP protocol version number, header length (bytes), "type" of data, max number of remaining hops, upper layer protocol to deliver payload to
- Overhead in IP datagram format
Network Layer Functions
- Host, router, and network layer functions: transport layer, IP protocol, routing protocols, network layer addressing conventions, datagram format, packet handling conventions, path selection, RIP, OSPF, BGP, forwarding table, ICMP protocol error reporting, router "signaling", link layer, and physical layer
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Description
This quiz provides an overview of Chapter 4 'Network Layer' from the textbook 'Network Layer 4-10'. It covers topics such as virtual circuit and datagram networks, router architecture, IP (Internet Protocol), routing algorithms, routing in the Internet, and broadcast and multicast routing.
