Term
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Definition
| (Frequency Division Multiplexing Access) is a method of dividing a single band into many discrete channels. |
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Term
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Definition
| End-to-end resources reserved for service ahead of time (setup required).Dedicated resources (or circuit) per call (ex: phone network) means no sharing, but guaranteed performance. Bandwidth is divided into “pieces” which are allocated to calls. If not being used, the piece is idle (NO sharing = waste here). Dividing link bandwidth into “pieces” involves either . . . |
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Term
| Protocols on the internet. . . |
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Definition
| define format, order of msgs sent and received among network entities, and actions taken on msg transmission/receipt. |
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Term
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Definition
| (Time Division Multiplexing Access) - divides a single channel into a few discrete time partitions of very few milliseconds at a time with each channel sending data in an (often) round robin fashion. Lots of overhead to keep timing right. |
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Term
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Definition
Each end-end data stream divided into packets. Allows more users than circuit switching.
Each packet uses full link bandwidth and resources are used as needed. Aggregate resource demand can exceed amount available, which requires management through: Congestion: packets queue, wait for link use or Store and forward: packets move one hop at a time: Transmit over link, Wait turn at next link |
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Term
| What are two ways of routing in Packet-switch networks? |
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Definition
Datagram network: Destination address determines next hop, meaning routes are fluid. Ex: asking directions.
Virtual circuit network:Each packet carries tag (virtual circuit ID) which determines next hop in the fixed path determined at call setup time. Routers maintain per-call state. |
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Term
| How to connect end systems to edge router? |
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Definition
| Residential access nets (cable company), institutional access local area networks (school, business), Mobile access networks, physically (radio WiFi, fiber) |
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Term
| 2 sources of delay (per hop) in order of contact: |
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Definition
Nodal processing: Check bit errors and Determine output link
Transmission: Time to send bits into link = L/R where: R = Link bandwidth (bps), L = Packet length (bits) |
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Term
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Definition
Queueing: Time waiting at output link for transmission; depends on congestion level of router
With R and L from ^ and a = Average packet arrival rate: Traffic intensity = La/R around 0 = Average queueing delay small, 1 = Delays become large, and > 1: More “work” arriving than can be serviced, average delay infinite!
Propagation: Delay due to the physical medium = d/s where: d = Length of physical link, s = propagation speed in medium (~2×108 m/sec) |
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Term
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Definition
Application: supporting network applications. Ex: FTP, SMTP, HTTP
Transport: host-host data transfer. Ex: TCP, UDP
Network: routing of datagrams from source to destination Ex: IP, routing protocols
Link: data transfer between neighboring network elements. Ex: PPP, Ethernet
Physical: bits “on the wire” or “over the air” |
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Term
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Definition
| (National/international backbone providers) - Interconnect (peer) with each other privately, or at public Network Access Point (NAPs). NBPs connect to Regional ISPs which connect to local ISPs. |
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