Renormalize files
This commit is contained in:
@ -1,59 +1,59 @@
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Lecture Topic: Bandwidth and Data Rate
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Analog: x(t)
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Discrete: x(n)
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Digital: from formula, range / set, bit sequence
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Bandwidth:
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$x(t) = \sum^{\infty}_{k=-\infty}A_k cos(2\pi f_k + \phi_k)$
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Fourier series
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Shannon Theorem:
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For a Gaussian channel the data rate that can be achieved over a channel of a given bandwidth satisfies
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$R \leq B_w log_2(1+\frac{S}{N}) \triangleq C$
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R = Achievable data rate (bps)
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$B_w$ = Channel bandwidth in Hz
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S/N = Signal to noise ratio (SNR)
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S = Signal power, N = noise power
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Internet Architecture:
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- Network Edge
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- End systems: Host apps, not only computers and mobile devices but also wearables, sensors and large servers
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- Access Networks: (Last hop, last mile), Connect end systems to the first router (aka edge router)
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- Network Core:
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- Packet switches: Routers, link layer switches
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A hierarchical look at A network of network:
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- Hosts connect to the internet via access ISPs, residential, cooperate ISPs, university ISPs, cellular data ISPs.
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- Access ISPs in turn are interconnected through regional ISPs and tier 1 ISPs
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(Diagram in slides)
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Internet Access and Physical Media:
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- Wired
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- Dial up
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- DSL
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- Cable
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- Fibre Optics
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- Ethernet
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- Wireless
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- WiFi
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- Cellular
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- Satellite
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Wired media: EM waves are guided along a solid medium (twisted pair copper, coaxial cable, fibre optics)
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Wireless media: EM waves propagate through the air (Different electromagnetic spectrum/frequency bands)
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Dial-Up:
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Use existing telephony infrastructure
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- Low Speed (56k)
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- Can't use phone and internet at the same time (not always present)
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- Modems modulate and demodulate data over phone lines
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DSL:
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Digital Subscriber Line
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Lecture Topic: Bandwidth and Data Rate
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|
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Analog: x(t)
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Discrete: x(n)
|
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Digital: from formula, range / set, bit sequence
|
||||
|
||||
Bandwidth:
|
||||
$x(t) = \sum^{\infty}_{k=-\infty}A_k cos(2\pi f_k + \phi_k)$
|
||||
|
||||
Fourier series
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||||
|
||||
|
||||
Shannon Theorem:
|
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For a Gaussian channel the data rate that can be achieved over a channel of a given bandwidth satisfies
|
||||
|
||||
$R \leq B_w log_2(1+\frac{S}{N}) \triangleq C$
|
||||
|
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R = Achievable data rate (bps)
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$B_w$ = Channel bandwidth in Hz
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S/N = Signal to noise ratio (SNR)
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S = Signal power, N = noise power
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|
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Internet Architecture:
|
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- Network Edge
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- End systems: Host apps, not only computers and mobile devices but also wearables, sensors and large servers
|
||||
- Access Networks: (Last hop, last mile), Connect end systems to the first router (aka edge router)
|
||||
- Network Core:
|
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- Packet switches: Routers, link layer switches
|
||||
|
||||
A hierarchical look at A network of network:
|
||||
- Hosts connect to the internet via access ISPs, residential, cooperate ISPs, university ISPs, cellular data ISPs.
|
||||
- Access ISPs in turn are interconnected through regional ISPs and tier 1 ISPs
|
||||
|
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(Diagram in slides)
|
||||
|
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Internet Access and Physical Media:
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- Wired
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- Dial up
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- DSL
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- Cable
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- Fibre Optics
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- Ethernet
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- Wireless
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- WiFi
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- Cellular
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- Satellite
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||||
|
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Wired media: EM waves are guided along a solid medium (twisted pair copper, coaxial cable, fibre optics)
|
||||
Wireless media: EM waves propagate through the air (Different electromagnetic spectrum/frequency bands)
|
||||
|
||||
Dial-Up:
|
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Use existing telephony infrastructure
|
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- Low Speed (56k)
|
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- Can't use phone and internet at the same time (not always present)
|
||||
- Modems modulate and demodulate data over phone lines
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|
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DSL:
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Digital Subscriber Line
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(Slides went fast)
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@ -1,53 +1,53 @@
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Lecture Topic: Network Edge & Internet Access Technologies
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|
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Bandwidth and Data Rate recap:
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The data rate cannot exceed the capacity of the bandwidth of a given channel, this is where the formula $R \leq B_w log_2(1+\frac{S}{N}) \triangleq C$ comes from
|
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|
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Doubling the data rate means that you need a bandwidth that has at least as much capacity to handle the new data rate
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|
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Internet Access Technologies:
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- DSL:
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- Using Frequency Division Multiplexing (FDM) it caries digital data through phone lines
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- Example: Voice 0-4 kHz, Upstream 4-50 kHz, Downstream 50 kHz-1 MHz
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- Twisted Pair Cable Wire:
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- Constitute a fine antenna
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- Cancel out cross talk and produce less radiation
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- A number of pairs are bundled together in a cable
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- Used in telephone systems, unheralded twisted pair (UTP) for local area networks, computer networks within a building (Ethernet)
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- Data Rate: 10Mbps - 10Gbps
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- Cable:
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- Use cable TV companies existing cable infrastructure
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- Hybrid fibre coaxial (HFC) access network
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- Coaxial cables are shared to reach individual homes
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- Fibre optics connect neighbourhood level junctions to CMTS
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- Asymmetric 40Mbps - 1.2Gbps downstream, 30Mbps - 100Mbps upstream
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- Data/TV are transmitted at different frequencies over shared cable
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- At the home, splits the signals into TV and Internet signals
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- Coaxial Cable
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- More complex structure
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- Better performance
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- Excellent noise immunity because cable is very shielded
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- Can span longer distances
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- Bandwidth is close to 1 Ghz
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- Data rates are higher than other technologies, 100s Mbps per channel
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- Fibre to the home (FTTH)
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- Optical network terminal in individual homes (ONT)
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- Optical line terminal in central office (OLT)
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- Fibre optic cables are similar to coax cables (lots of layers)
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- Class core with higher index of refraction than the outer glass
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- Light propagates through glass core
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- Thin plastic jacket to protect glass cladding
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- Fibres are typically grouped in bundles protected by an outer sheath
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- The outer layer keeps the light inside, not leaking any energy by reflecting the signal off an outer sheath
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- Has a few excellent features:
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- Very low signal attenuation up to 100km
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- Immune to electromagnetic interference
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- Larger bandwidth, support data rate up to 10s or 100s of Gbps
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- Hard to tap
|
||||
|
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Network Core:
|
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- How is data moved through a network of links and packet switches?
|
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- There are two fundamental approaches
|
||||
- Circuit switching
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||||
- Packet switching
|
||||
Lecture Topic: Network Edge & Internet Access Technologies
|
||||
|
||||
Bandwidth and Data Rate recap:
|
||||
The data rate cannot exceed the capacity of the bandwidth of a given channel, this is where the formula $R \leq B_w log_2(1+\frac{S}{N}) \triangleq C$ comes from
|
||||
|
||||
Doubling the data rate means that you need a bandwidth that has at least as much capacity to handle the new data rate
|
||||
|
||||
Internet Access Technologies:
|
||||
- DSL:
|
||||
- Using Frequency Division Multiplexing (FDM) it caries digital data through phone lines
|
||||
- Example: Voice 0-4 kHz, Upstream 4-50 kHz, Downstream 50 kHz-1 MHz
|
||||
- Twisted Pair Cable Wire:
|
||||
- Constitute a fine antenna
|
||||
- Cancel out cross talk and produce less radiation
|
||||
- A number of pairs are bundled together in a cable
|
||||
- Used in telephone systems, unheralded twisted pair (UTP) for local area networks, computer networks within a building (Ethernet)
|
||||
- Data Rate: 10Mbps - 10Gbps
|
||||
- Cable:
|
||||
- Use cable TV companies existing cable infrastructure
|
||||
- Hybrid fibre coaxial (HFC) access network
|
||||
- Coaxial cables are shared to reach individual homes
|
||||
- Fibre optics connect neighbourhood level junctions to CMTS
|
||||
- Asymmetric 40Mbps - 1.2Gbps downstream, 30Mbps - 100Mbps upstream
|
||||
- Data/TV are transmitted at different frequencies over shared cable
|
||||
- At the home, splits the signals into TV and Internet signals
|
||||
- Coaxial Cable
|
||||
- More complex structure
|
||||
- Better performance
|
||||
- Excellent noise immunity because cable is very shielded
|
||||
- Can span longer distances
|
||||
- Bandwidth is close to 1 Ghz
|
||||
- Data rates are higher than other technologies, 100s Mbps per channel
|
||||
- Fibre to the home (FTTH)
|
||||
- Optical network terminal in individual homes (ONT)
|
||||
- Optical line terminal in central office (OLT)
|
||||
- Fibre optic cables are similar to coax cables (lots of layers)
|
||||
- Class core with higher index of refraction than the outer glass
|
||||
- Light propagates through glass core
|
||||
- Thin plastic jacket to protect glass cladding
|
||||
- Fibres are typically grouped in bundles protected by an outer sheath
|
||||
- The outer layer keeps the light inside, not leaking any energy by reflecting the signal off an outer sheath
|
||||
- Has a few excellent features:
|
||||
- Very low signal attenuation up to 100km
|
||||
- Immune to electromagnetic interference
|
||||
- Larger bandwidth, support data rate up to 10s or 100s of Gbps
|
||||
- Hard to tap
|
||||
|
||||
Network Core:
|
||||
- How is data moved through a network of links and packet switches?
|
||||
- There are two fundamental approaches
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- Circuit switching
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- Packet switching
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-
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@ -1,42 +1,42 @@
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Lecture Topic: Network Core
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Resource Sharing with circuit switching:
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- Network resources divided into pieces allocated to connections
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- Frequency division multiplexing (FDM). Dividing over bandwidth, and each end user gets a portion of the bandwidth for the entire portion of time.
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- Time division multiplexing (TDM). Dividing over time, and each end user gets the full bandwidth for a portion of allocated time. Similar to round robin.
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Table of some information of cellular network technologies:
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CS: Circuit Switching
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1G (FDMA)
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2G (TDMA) (GSM/CS)
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3G (CDMA) (CS/PS)
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4G (PS)
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5G (millimeter wave)
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With circuit switching you can guarantee a certain level of performance, while with packet switching there is no/less of a guarantee of performance, which is why circuit switching was important for mobile networks as emergency calls need a certain level of performance to be guaranteed.
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Packet Switching:
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- Internet is based on packet switching
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- ARPANET was the first packet-switched network and is an ancestor of the internet
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- A sending host breaks a message into packets (numbered sequentially) and sends them into the network one by one
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||||
- Packets are transmitted individually through the network and reassembled at the receiving host to recover the original message
|
||||
|
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Packet switching is a very adaptive to changing network conditions. Due to packet chunking, packets in transit can be routed through different routes depending on the used bandwidth of other nodes on the network, and this can occur between two packets of the same chunk of data. This is because packets are numbered and are reordered at the destination.
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A packet follows a path:
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- First hop router: This is the first router that inspects the packet and forwards it to the next hop
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- Then next router does the same, and so on
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- The packets eventually arrives at the destination and are decoded
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Packets follow a protocol called "store and forward"
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|
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Resource sharing with packet switching:
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- Is very easy, as you can just send all packets over a link, according to different priorities
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||||
|
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Multiplexing comparison:
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||||
- With circuit switching, if you allocate bandwidth to two services, it may end up unused and wasted, as the format of data is fixed and if service A is not using any traffic service B cannot use that other bandwidth
|
||||
- Statistical multiplexing: Packet switching is on demand, so no bandwidth is explicitly allocated, and bandwidth is dynamically allocated based on current network usage
|
||||
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There are some downsides to packet switching to be aware of however:
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Lecture Topic: Network Core
|
||||
|
||||
Resource Sharing with circuit switching:
|
||||
- Network resources divided into pieces allocated to connections
|
||||
- Frequency division multiplexing (FDM). Dividing over bandwidth, and each end user gets a portion of the bandwidth for the entire portion of time.
|
||||
- Time division multiplexing (TDM). Dividing over time, and each end user gets the full bandwidth for a portion of allocated time. Similar to round robin.
|
||||
|
||||
Table of some information of cellular network technologies:
|
||||
CS: Circuit Switching
|
||||
|
||||
1G (FDMA)
|
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2G (TDMA) (GSM/CS)
|
||||
3G (CDMA) (CS/PS)
|
||||
4G (PS)
|
||||
5G (millimeter wave)
|
||||
|
||||
With circuit switching you can guarantee a certain level of performance, while with packet switching there is no/less of a guarantee of performance, which is why circuit switching was important for mobile networks as emergency calls need a certain level of performance to be guaranteed.
|
||||
|
||||
Packet Switching:
|
||||
- Internet is based on packet switching
|
||||
- ARPANET was the first packet-switched network and is an ancestor of the internet
|
||||
- A sending host breaks a message into packets (numbered sequentially) and sends them into the network one by one
|
||||
- Packets are transmitted individually through the network and reassembled at the receiving host to recover the original message
|
||||
|
||||
Packet switching is a very adaptive to changing network conditions. Due to packet chunking, packets in transit can be routed through different routes depending on the used bandwidth of other nodes on the network, and this can occur between two packets of the same chunk of data. This is because packets are numbered and are reordered at the destination.
|
||||
|
||||
A packet follows a path:
|
||||
- First hop router: This is the first router that inspects the packet and forwards it to the next hop
|
||||
- Then next router does the same, and so on
|
||||
- The packets eventually arrives at the destination and are decoded
|
||||
|
||||
Packets follow a protocol called "store and forward"
|
||||
|
||||
Resource sharing with packet switching:
|
||||
- Is very easy, as you can just send all packets over a link, according to different priorities
|
||||
|
||||
Multiplexing comparison:
|
||||
- With circuit switching, if you allocate bandwidth to two services, it may end up unused and wasted, as the format of data is fixed and if service A is not using any traffic service B cannot use that other bandwidth
|
||||
- Statistical multiplexing: Packet switching is on demand, so no bandwidth is explicitly allocated, and bandwidth is dynamically allocated based on current network usage
|
||||
|
||||
There are some downsides to packet switching to be aware of however:
|
||||
- In next lecture
|
||||
@ -1,56 +1,56 @@
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Lecture Topic: Packet Switching Performance
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# Packet Switching
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## Congestion
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A relevant example is air plane ticket overbooking. If an air plane has a capacity of 100 seats, and the probability of of a passenger showing up to their flight is 80%, then you can overbook ticket sales due to the probability of passengers not showing up
|
||||
- If 110 tickets are sold, the probability of more than 100 passengers is 0.0058%
|
||||
- If 115 tickets are sold, the probability goes up to 1.94%
|
||||
- If 120 tickets are sold, the probability is 15.17%
|
||||
- If 130 tickets are sold, the probability is 78.12%
|
||||
|
||||
## Performance
|
||||
Throughput: Rate (bits/time) at which bits are transferred between sender/receiver
|
||||
- Instantaneous: Receiving rate at any instant of time
|
||||
- Average: Receiving rate over a longer period of time
|
||||
|
||||
How fast a node (host or router) is transmitting depends on
|
||||
1. How fast the sender is sending
|
||||
2. How fast the link is transmitting
|
||||
|
||||
End-to-end throughput is constrained by rate of bottleneck link (the link of the minimum rate on an end-to-end path). The weakest link in the chain (of nodes) determines the throughput of the entire link.
|
||||
|
||||
## Delay and Loss
|
||||
Packets queue in a router buffer (Store and Forward)
|
||||
- They are delayed while waiting in the buffer for it's turn
|
||||
- Slowed down while the queue keeps growing (congestion)
|
||||
- Dropped (lost) if no free space in a full buffer
|
||||
|
||||
There is four sources of nodal delay:
|
||||
1. Node processing: Decoding the incoming electronic signal and accounting for distortion (e.g. wireless signal distortion), and verifying the correctness of the packet, and determining the output link. Usually very small ($10^{-6}$ secs)
|
||||
2. Queuing: Time waiting at the output link for transmission. Amount depends on the congestion of the network.
|
||||
3. Transmission: $L/R$, L = Packet length, R = Link bandwidth
|
||||
4. Propagation: $m/s$ m = Physical distance of link (e.g. 100m wire), s = propagation speed of link (e.g. speed of electricity)
|
||||
|
||||
The entire delay is the sum of all of these figures
|
||||
|
||||
### Measuring queuing delay
|
||||
Traffic intensity is a measure of congestion.
|
||||
$$ \frac{L \times a}{R} $$
|
||||
a: Average packet arrive rate (packets/s)
|
||||
L: Packet length/size (bits/packet)
|
||||
R: Link bandwidth/rate (bps)
|
||||
|
||||
If this figure is 0, the delay on average is very small
|
||||
If this figure is 1, the delay is large
|
||||
If this figure is > 1, then more work arriving than serviced (severe congestion)
|
||||
|
||||
Note: There is a field called traffic engineering, and an important rule for this field is to not let the traffic intensity exceed 1.
|
||||
|
||||
## Example: Delay
|
||||
Consider only transmission delay and propagation delay. S sends 1 packet of length L to D over a single link of rate R and distance m. s is the speed of the link
|
||||
|
||||
L = 1 kb
|
||||
R = 100 kb/s
|
||||
m = 100 km
|
||||
s = $2\times10^8$ m/s
|
||||
|
||||
Lecture Topic: Packet Switching Performance
|
||||
# Packet Switching
|
||||
## Congestion
|
||||
A relevant example is air plane ticket overbooking. If an air plane has a capacity of 100 seats, and the probability of of a passenger showing up to their flight is 80%, then you can overbook ticket sales due to the probability of passengers not showing up
|
||||
- If 110 tickets are sold, the probability of more than 100 passengers is 0.0058%
|
||||
- If 115 tickets are sold, the probability goes up to 1.94%
|
||||
- If 120 tickets are sold, the probability is 15.17%
|
||||
- If 130 tickets are sold, the probability is 78.12%
|
||||
|
||||
## Performance
|
||||
Throughput: Rate (bits/time) at which bits are transferred between sender/receiver
|
||||
- Instantaneous: Receiving rate at any instant of time
|
||||
- Average: Receiving rate over a longer period of time
|
||||
|
||||
How fast a node (host or router) is transmitting depends on
|
||||
1. How fast the sender is sending
|
||||
2. How fast the link is transmitting
|
||||
|
||||
End-to-end throughput is constrained by rate of bottleneck link (the link of the minimum rate on an end-to-end path). The weakest link in the chain (of nodes) determines the throughput of the entire link.
|
||||
|
||||
## Delay and Loss
|
||||
Packets queue in a router buffer (Store and Forward)
|
||||
- They are delayed while waiting in the buffer for it's turn
|
||||
- Slowed down while the queue keeps growing (congestion)
|
||||
- Dropped (lost) if no free space in a full buffer
|
||||
|
||||
There is four sources of nodal delay:
|
||||
1. Node processing: Decoding the incoming electronic signal and accounting for distortion (e.g. wireless signal distortion), and verifying the correctness of the packet, and determining the output link. Usually very small ($10^{-6}$ secs)
|
||||
2. Queuing: Time waiting at the output link for transmission. Amount depends on the congestion of the network.
|
||||
3. Transmission: $L/R$, L = Packet length, R = Link bandwidth
|
||||
4. Propagation: $m/s$ m = Physical distance of link (e.g. 100m wire), s = propagation speed of link (e.g. speed of electricity)
|
||||
|
||||
The entire delay is the sum of all of these figures
|
||||
|
||||
### Measuring queuing delay
|
||||
Traffic intensity is a measure of congestion.
|
||||
$$ \frac{L \times a}{R} $$
|
||||
a: Average packet arrive rate (packets/s)
|
||||
L: Packet length/size (bits/packet)
|
||||
R: Link bandwidth/rate (bps)
|
||||
|
||||
If this figure is 0, the delay on average is very small
|
||||
If this figure is 1, the delay is large
|
||||
If this figure is > 1, then more work arriving than serviced (severe congestion)
|
||||
|
||||
Note: There is a field called traffic engineering, and an important rule for this field is to not let the traffic intensity exceed 1.
|
||||
|
||||
## Example: Delay
|
||||
Consider only transmission delay and propagation delay. S sends 1 packet of length L to D over a single link of rate R and distance m. s is the speed of the link
|
||||
|
||||
L = 1 kb
|
||||
R = 100 kb/s
|
||||
m = 100 km
|
||||
s = $2\times10^8$ m/s
|
||||
|
||||
$d_{prop} = m/s = 10^5/(2\times 10^8) = 5 \times 10^{-4}$
|
||||
@ -1,61 +1,61 @@
|
||||
Lecture Topic: Delay and Internet Layering
|
||||
|
||||
# Single Packet over Same Rate Links
|
||||
If each node has the same rate, and you consider only transmission delay, what is the end to end delay to send one packet of length L?
|
||||
|
||||
# 4 Packets over 2 Same Rate Links
|
||||
$d_{trans} = (L/R) = \tau$
|
||||
$d_{e2e} = 5\tau$
|
||||
Visual in slides
|
||||
|
||||
Two phases:
|
||||
- Phase 1 has transmitted P-1 packets out
|
||||
- Phase 2 has 1 Packet left
|
||||
$$(P + N) \times \tau = d_{e2e}$$
|
||||
|
||||
# 4 Packets over 2 Links of different rates
|
||||
$$d_{e2e} \approx \frac{\text{Total package size}}{\text{E2E throughput}}$$
|
||||
So, estimating
|
||||
$d_{e2e} \approx \frac{4 \times L}{R} = 4\tau$
|
||||
while the real end to end delay is $5\tau$
|
||||
|
||||
# Internet Layering
|
||||
Also called TCP/IP model
|
||||
## Layers (inverse order due to markdown)
|
||||
1. Application
|
||||
2. Transport
|
||||
3. Network
|
||||
4. Link
|
||||
5. Physical
|
||||
## Applications
|
||||
- SMTP
|
||||
- HTTP
|
||||
- DNS
|
||||
## Transport
|
||||
- UDP
|
||||
- TCP
|
||||
## Network
|
||||
- IP
|
||||
- Routing protocols
|
||||
## Link
|
||||
- Ethernet
|
||||
- WiFi
|
||||
## Physical
|
||||
- Moving individual bits from one node to the next
|
||||
|
||||
Terms:
|
||||
- Router (Operates on network layer)
|
||||
- Switch (Operates on link layer)
|
||||
- Modem (Modulation, converting mediums and modes)
|
||||
- Access Point (WiFi access)
|
||||
|
||||
## Protocols
|
||||
Define how peers communicate and exchange information over the network including rules, procedures, and message formats
|
||||
|
||||
Application layer protocols:
|
||||
- Web server to web client (HTTP)
|
||||
|
||||
(More examples for each layer in slides)
|
||||
|
||||
### Encapsulation
|
||||
Lecture Topic: Delay and Internet Layering
|
||||
|
||||
# Single Packet over Same Rate Links
|
||||
If each node has the same rate, and you consider only transmission delay, what is the end to end delay to send one packet of length L?
|
||||
|
||||
# 4 Packets over 2 Same Rate Links
|
||||
$d_{trans} = (L/R) = \tau$
|
||||
$d_{e2e} = 5\tau$
|
||||
Visual in slides
|
||||
|
||||
Two phases:
|
||||
- Phase 1 has transmitted P-1 packets out
|
||||
- Phase 2 has 1 Packet left
|
||||
$$(P + N) \times \tau = d_{e2e}$$
|
||||
|
||||
# 4 Packets over 2 Links of different rates
|
||||
$$d_{e2e} \approx \frac{\text{Total package size}}{\text{E2E throughput}}$$
|
||||
So, estimating
|
||||
$d_{e2e} \approx \frac{4 \times L}{R} = 4\tau$
|
||||
while the real end to end delay is $5\tau$
|
||||
|
||||
# Internet Layering
|
||||
Also called TCP/IP model
|
||||
## Layers (inverse order due to markdown)
|
||||
1. Application
|
||||
2. Transport
|
||||
3. Network
|
||||
4. Link
|
||||
5. Physical
|
||||
## Applications
|
||||
- SMTP
|
||||
- HTTP
|
||||
- DNS
|
||||
## Transport
|
||||
- UDP
|
||||
- TCP
|
||||
## Network
|
||||
- IP
|
||||
- Routing protocols
|
||||
## Link
|
||||
- Ethernet
|
||||
- WiFi
|
||||
## Physical
|
||||
- Moving individual bits from one node to the next
|
||||
|
||||
Terms:
|
||||
- Router (Operates on network layer)
|
||||
- Switch (Operates on link layer)
|
||||
- Modem (Modulation, converting mediums and modes)
|
||||
- Access Point (WiFi access)
|
||||
|
||||
## Protocols
|
||||
Define how peers communicate and exchange information over the network including rules, procedures, and message formats
|
||||
|
||||
Application layer protocols:
|
||||
- Web server to web client (HTTP)
|
||||
|
||||
(More examples for each layer in slides)
|
||||
|
||||
### Encapsulation
|
||||
Messages get passed down between each layer, and information gets appended to the header that gets delivered as the payload
|
||||
@ -1,34 +1,34 @@
|
||||
Lecture Topic: Web Protocols
|
||||
# Encapsulation/Decapsulation
|
||||
Each layer of a network adds a header, that encapsulates the rest of the data
|
||||
When a packet is decapsulated, each layer strips away its header after it is done processing
|
||||
|
||||
# Network Applications
|
||||
Applications are *distributed* since they involve multiple end systems that exchange dat which each other
|
||||
|
||||
## Application Architectures
|
||||
Dictates how applications interact on a network
|
||||
- Client/Server architecture
|
||||
- Server: An always on host which services requests from many other hosts
|
||||
- Data is often stored on the server
|
||||
- Data centers can be used to create powerful virtual servers
|
||||
- Clients: Connect through to the server
|
||||
- Peer to peer architecture
|
||||
- No always on server
|
||||
- Arbitrary end systems directly communicate
|
||||
- Peers request service from other peers and provide service in return to other peers
|
||||
- Self scalability: New peers bring new service capacity as well as new service demands
|
||||
- Peers are intermittently connected and change IP addresses (complex management)
|
||||
- Examples include BitTorrent (P2P file sharing)
|
||||
|
||||
# Basics of Web and HTTP
|
||||
Invented by Tim Burners-Lee
|
||||
Client Server model
|
||||
- Client is a web browser that requests and receives, and then displays web objects
|
||||
- Server is a web server that sends objects in response to
|
||||
|
||||
## HTTP Request Structure
|
||||
Diagram in slides (Just info from Wikipedia)
|
||||
|
||||
## HTTP Responses
|
||||
Lecture Topic: Web Protocols
|
||||
# Encapsulation/Decapsulation
|
||||
Each layer of a network adds a header, that encapsulates the rest of the data
|
||||
When a packet is decapsulated, each layer strips away its header after it is done processing
|
||||
|
||||
# Network Applications
|
||||
Applications are *distributed* since they involve multiple end systems that exchange dat which each other
|
||||
|
||||
## Application Architectures
|
||||
Dictates how applications interact on a network
|
||||
- Client/Server architecture
|
||||
- Server: An always on host which services requests from many other hosts
|
||||
- Data is often stored on the server
|
||||
- Data centers can be used to create powerful virtual servers
|
||||
- Clients: Connect through to the server
|
||||
- Peer to peer architecture
|
||||
- No always on server
|
||||
- Arbitrary end systems directly communicate
|
||||
- Peers request service from other peers and provide service in return to other peers
|
||||
- Self scalability: New peers bring new service capacity as well as new service demands
|
||||
- Peers are intermittently connected and change IP addresses (complex management)
|
||||
- Examples include BitTorrent (P2P file sharing)
|
||||
|
||||
# Basics of Web and HTTP
|
||||
Invented by Tim Burners-Lee
|
||||
Client Server model
|
||||
- Client is a web browser that requests and receives, and then displays web objects
|
||||
- Server is a web server that sends objects in response to
|
||||
|
||||
## HTTP Request Structure
|
||||
Diagram in slides (Just info from Wikipedia)
|
||||
|
||||
## HTTP Responses
|
||||
List found in slides (just info from Wikipedia)
|
||||
@ -1,17 +1,17 @@
|
||||
Lecture Topic: HTTP
|
||||
|
||||
# Conditional Get
|
||||
## Last-Modified
|
||||
You can check the Last-Modified header to only get contents if the contents are newer than the contents of the cache
|
||||
## ETag
|
||||
Use the hash of an object to check for modification to solve cache invalidation problem
|
||||
|
||||
## TCP and HTTP
|
||||
HTTP runs on top of TCP
|
||||
- Client initiates TCP request to server
|
||||
- Server accepts TCP connection
|
||||
- Clint confirms request
|
||||
- Three way handshake
|
||||
|
||||
## Non-persistent HTTP
|
||||
RTT = Round trip time
|
||||
Lecture Topic: HTTP
|
||||
|
||||
# Conditional Get
|
||||
## Last-Modified
|
||||
You can check the Last-Modified header to only get contents if the contents are newer than the contents of the cache
|
||||
## ETag
|
||||
Use the hash of an object to check for modification to solve cache invalidation problem
|
||||
|
||||
## TCP and HTTP
|
||||
HTTP runs on top of TCP
|
||||
- Client initiates TCP request to server
|
||||
- Server accepts TCP connection
|
||||
- Clint confirms request
|
||||
- Three way handshake
|
||||
|
||||
## Non-persistent HTTP
|
||||
RTT = Round trip time
|
||||
|
||||
@ -1,26 +1,26 @@
|
||||
Lecture Topic: Advanced HTTP
|
||||
|
||||
# HTTP2
|
||||
Goal is to reduce latency, but keep the same methods, status codes, and header fields. Changes how data is formatted and transmitted between clients
|
||||
- Prioritises transmission of requested objects, and give a request a weight to each request to indicate priority
|
||||
- Server pushes additional objects to client, by sending multiple responses to a single client request, before receiving explicit
|
||||
- Head of line blocking
|
||||
- Before in HTTP 1.1 the request are blocked by large requests, as objects are delivered in sequence, and a workaround is to setup multiple TCP connections to request many objects at once
|
||||
- In version 2, objects are divided into *frames* and frame transmission is interleaved in a round robin fashion
|
||||
|
||||
# HTTP3
|
||||
Improved performance even further by using streaming, by using the "QUIC" protocol over a bare UDP connection
|
||||
|
||||
# HTML Versions
|
||||
- HTML 1.0 Is written by Tim Berners-Lee
|
||||
- HTML 1,2,3,4, 4.01 published in in 1999
|
||||
- XHTML is an extensible version of HTML, based on XML
|
||||
- HTML5
|
||||
- New elements, section for documents, figure for content flow, video, audio, canvas for multimedia
|
||||
- New APIs to prompt users, like alert(), confirm(), prompt(), and printing with print()
|
||||
HTML is a markup language that uses tags
|
||||
|
||||
(list and explanation of common html tags)
|
||||
|
||||
# CSS
|
||||
Lecture Topic: Advanced HTTP
|
||||
|
||||
# HTTP2
|
||||
Goal is to reduce latency, but keep the same methods, status codes, and header fields. Changes how data is formatted and transmitted between clients
|
||||
- Prioritises transmission of requested objects, and give a request a weight to each request to indicate priority
|
||||
- Server pushes additional objects to client, by sending multiple responses to a single client request, before receiving explicit
|
||||
- Head of line blocking
|
||||
- Before in HTTP 1.1 the request are blocked by large requests, as objects are delivered in sequence, and a workaround is to setup multiple TCP connections to request many objects at once
|
||||
- In version 2, objects are divided into *frames* and frame transmission is interleaved in a round robin fashion
|
||||
|
||||
# HTTP3
|
||||
Improved performance even further by using streaming, by using the "QUIC" protocol over a bare UDP connection
|
||||
|
||||
# HTML Versions
|
||||
- HTML 1.0 Is written by Tim Berners-Lee
|
||||
- HTML 1,2,3,4, 4.01 published in in 1999
|
||||
- XHTML is an extensible version of HTML, based on XML
|
||||
- HTML5
|
||||
- New elements, section for documents, figure for content flow, video, audio, canvas for multimedia
|
||||
- New APIs to prompt users, like alert(), confirm(), prompt(), and printing with print()
|
||||
HTML is a markup language that uses tags
|
||||
|
||||
(list and explanation of common html tags)
|
||||
|
||||
# CSS
|
||||
CSS defines the visual style of a document
|
||||
@ -1,3 +1,3 @@
|
||||
Lecture Topic: File Distribution
|
||||
|
||||
Lecture Topic: File Distribution
|
||||
|
||||
Studying for test in CS2333, view info on slides
|
||||
@ -1,7 +1,7 @@
|
||||
Lecture Topic: P2P and File sharing, DNS
|
||||
|
||||
BitTorrent uses the rarest first algorithm to distribute chunks
|
||||
|
||||
Sending chunks uses the tit-for-tat algorithm to evaluate neighbours for sending chunks
|
||||
|
||||
Lecture Topic: P2P and File sharing, DNS
|
||||
|
||||
BitTorrent uses the rarest first algorithm to distribute chunks
|
||||
|
||||
Sending chunks uses the tit-for-tat algorithm to evaluate neighbours for sending chunks
|
||||
|
||||
DNS is a distributed database implemented in a hierarchy of name-servers
|
||||
@ -1 +1 @@
|
||||
Lecture Topic: DNS
|
||||
Lecture Topic: DNS
|
||||
|
||||
@ -1,16 +1,16 @@
|
||||
Lecture Topic: Transport Layer overview
|
||||
|
||||
Socket information is a tuple, port number is important
|
||||
|
||||
# Transport Layer
|
||||
## UDP
|
||||
Connectionless transport protocol, no handshake, each segment is handled independently from others
|
||||
|
||||
UDP segment is very simple: an 8 byte header and a payload.
|
||||
It has a source port, destination port, length and checksum
|
||||
|
||||
The checksum in UDP is only for detection, not correction
|
||||
|
||||
As messages are transported through layers, they acquire new headers that wrap the existing packet
|
||||
|
||||
Lecture Topic: Transport Layer overview
|
||||
|
||||
Socket information is a tuple, port number is important
|
||||
|
||||
# Transport Layer
|
||||
## UDP
|
||||
Connectionless transport protocol, no handshake, each segment is handled independently from others
|
||||
|
||||
UDP segment is very simple: an 8 byte header and a payload.
|
||||
It has a source port, destination port, length and checksum
|
||||
|
||||
The checksum in UDP is only for detection, not correction
|
||||
|
||||
As messages are transported through layers, they acquire new headers that wrap the existing packet
|
||||
|
||||
Checksum in UDP is actually optional but is required in TCP and IPv4
|
||||
@ -1,5 +1,5 @@
|
||||
Lecture Topic: UDP and Reliable Data Transfer
|
||||
|
||||
Uses 1's compliment sum to do check-summing (info in slides)
|
||||
|
||||
Lecture Topic: UDP and Reliable Data Transfer
|
||||
|
||||
Uses 1's compliment sum to do check-summing (info in slides)
|
||||
|
||||
You use a system where you can imply the NACK request in packets, for example in TCP, NACKs are implied
|
||||
@ -1,4 +1,4 @@
|
||||
Lecture Topic: Reliable Data Transfer and TCP
|
||||
|
||||
Look at utilisation slides from notes, has formulas
|
||||
|
||||
Lecture Topic: Reliable Data Transfer and TCP
|
||||
|
||||
Look at utilisation slides from notes, has formulas
|
||||
|
||||
|
||||
@ -1,3 +1,3 @@
|
||||
Lecture Topic: TCP and TCP connection management
|
||||
|
||||
Lecture Topic: TCP and TCP connection management
|
||||
|
||||
Look at slides
|
||||
@ -1,22 +1,22 @@
|
||||
Lecture Topic: Midterm Review and TCP
|
||||
# Midterm
|
||||
## Format:
|
||||
- Multiple Choice questions
|
||||
- 5 MCQ, 5 Short and Numerical Questions (ish)
|
||||
- Concept and numerical questions
|
||||
- No formula sheet, no unit table, need to memorise
|
||||
## Delivery:
|
||||
- Closed book, calculators needed
|
||||
- Monday Feb 26th
|
||||
- ITD 414 (even student number)
|
||||
- ITD 415 (odd student number)
|
||||
## Coverage:
|
||||
All material up to today
|
||||
- Chapter 1 - 3
|
||||
Preparation Material
|
||||
- Lecture Slides
|
||||
- Review Exam
|
||||
|
||||
## Review:
|
||||
Went over review slides, going too fast to take notes
|
||||
|
||||
Lecture Topic: Midterm Review and TCP
|
||||
# Midterm
|
||||
## Format:
|
||||
- Multiple Choice questions
|
||||
- 5 MCQ, 5 Short and Numerical Questions (ish)
|
||||
- Concept and numerical questions
|
||||
- No formula sheet, no unit table, need to memorise
|
||||
## Delivery:
|
||||
- Closed book, calculators needed
|
||||
- Monday Feb 26th
|
||||
- ITD 414 (even student number)
|
||||
- ITD 415 (odd student number)
|
||||
## Coverage:
|
||||
All material up to today
|
||||
- Chapter 1 - 3
|
||||
Preparation Material
|
||||
- Lecture Slides
|
||||
- Review Exam
|
||||
|
||||
## Review:
|
||||
Went over review slides, going too fast to take notes
|
||||
|
||||
|
||||
@ -1,13 +1,13 @@
|
||||
Exam Review
|
||||
3 Hour Closed Book
|
||||
Calculator allowed and needed
|
||||
Q1 - Multiple Choice Questions (10 points)
|
||||
Q2-Q8 - Numerical and discussion questions (45 points)
|
||||
Prep Resources:
|
||||
Practice Test
|
||||
Slides
|
||||
Past Work
|
||||
Textbook
|
||||
|
||||
What will be on the exam is on review slides
|
||||
|
||||
Exam Review
|
||||
3 Hour Closed Book
|
||||
Calculator allowed and needed
|
||||
Q1 - Multiple Choice Questions (10 points)
|
||||
Q2-Q8 - Numerical and discussion questions (45 points)
|
||||
Prep Resources:
|
||||
Practice Test
|
||||
Slides
|
||||
Past Work
|
||||
Textbook
|
||||
|
||||
What will be on the exam is on review slides
|
||||
|
||||
|
||||
Reference in New Issue
Block a user