ICOM6012 Internet Infrastructure Technologies

Topic 2 The Big Picture

The Internet: “nuts and bolts” view

• Billions of connected computing devices
  • Host = end system
  • Running network apps
  • Internet of things (IoT)
• Packet switches
  • routers
  • switchers
• Communication links
  • Fiber, copper, radio, satellite
  • Transmission rate: bandwidth
• Networks
  • Collection of devices, routers, switches, links
  • Managed by an organization
• Internet: “network of networks”
  • Interconnected ISPs
• Protocols
  • Control sending, receiving of messages
• Internet standards
  • RFC: Requests for Comments
  • IETF: Internet Engineering Task Force
  • IEEE: Institute of Electronical & Electronic Engineering

The Internet: a “service” view

• Infrastructure
  • Web
  • Streaming video
  • Multimedia teleconferencing
  • Email
  • Games
  • E‐Commerce
  • Social media
  • Inter‐connected appliances
  • …
• Programming interface
  • Sending/receiving apps
  • Service options

Protocol

• Activities in the Internet involving two or more remote entities are governed by a protocol
• Protocols are running everywhere in the Internet

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

Network Standards

• IETF
  • Application
  • Transport
  • Network
• IEEE
  • Data link
  • Physical

Network Edge

• Hosts
  • Clients
  • Servers (always in data centers)

Access Networks, Physical Media

• Residential access networks (cable-based)
  • Frequency Division Multiplexing (FDM)
    • Different channels transmitted in different frequency bands
    • Modem = Modulator + Demodulator
      • A device that converts data from digital format into one suitable for a transmission medium
  • HFC: hybrid fiber coax
    • Asymmetric: up to 40 Mbps – 1.2 Gbs downstream transmission rate, 30‐100 Mbps upstream transmission rate
  • Network of cable, fiber attaches homes to ISP router
    • Homes share access network to cable headend
• Residential access networks: digital subscriber line (DSL)
  • Use existing telephone line to central office DSLAM
    • Data over DSL phone line goes to Internet
    • Voice over DSL phone line goes to telephone network
• Wireless access networks
  • Wireless local area networks (WLANs)
    • Within or around building (~100ft)
    • 802.11b/g/n (WiFi) - 11,54,450 Mbps
  • Wide-area cellular access networks
    • Mobile (10km)
    • 4G/5G cellular networks - 10 Mbps
  • IoT
    • BLE
    • ZigBee
    • LoRa
  • Remote areas
    • Satellite network: Geosynchronous Equatorial Orbit (GEO)
      • 35,786 km above equator
      • Large RTT (Round trip time): 0.5s
      • Expensive
      • Slow
      • Examples
        • “Project Loon” – Google
        • Starlink ‐‐ SpaceX
• Enterprise access networks (school, company)
  • Mix of wired, wireless link technologies
    • Ethernet
      • Wired access at 100Mbps, 1Gbps, 10Gbps
    • WiFi
      • Wireless access points at 11, 54, 450 Mbps

History of IEEE 802.11 (Use CSMA/CA)

• Unlicensed ISM - 1985
• 802.11 - 1997
  • 2.4GHz
  • DSSS & FHSS
  • 1,2Mbps
• 802.11b - 1999 (WiFi-1)
  • 2.4GHz
  • DSSS
  • 11Mbps
• 802.11a - 1999 (WiFi-2)
  • 5GHz
  • OFDM
  • 54Mbps
• WiFi Alliance - 1999
• 802.11g - 2003 (WiFi-3)
  • 2.4GHz
  • 54Mbps
• 802.11-2007 - 2007
  • Combined 802.11a/b/g
• 802.11n - 2009 (WiFi-4)
  • MIMO, 2.4 or 5GHz
  • 600Mbps
• 802.11-2012
  • Combined 802.11a/b/g/n
• 802.11ac - 2013 (WiFi-5)
  • 5GHz
  • 7Gbps
• 802.11ah - 2017
• 802.11ax - 2020 (WiFi-6)
  • 5GHz
  • OFDMA
  • 9.6Gbps

Links: Physical Media

• Twisted pair (TP)
  • Two insulated copper wires
    • Category 5: 100Mbos, 1Gbps Ethernet
    • Category 6: 10Gbps Ethernet
• Coaxial cable
  • Two concentric copper conductors
  • Bidiretional
  • Broadband
    • Multiple frequency channels on cable
    • 100 Mbps per channel
• Fiber optic cable
  • Glass fiber carrying light pulse a bit (each pulse a bit)
  • High-speed point-to-point transmission (10-100Gbps)
  • Low error rate
    • Repeaters spaced far apart
    • Immune to electromagnetic noise
• Wireless radio
  • Signal carried in electromagnetic spectrum
  • No physical “wire”
  • Propagation environment effects
    • Reflection
    • Obstruction by objects
    • Interference

Network Core

Mesh of interconnected routers

• Packet-switching (hosts break application-layer messages into packets)

  • Forward packets from one router to the next
  • Each packet transmitted a full link capacity

• Packet transmission delay

	Packet transmission delay = L (bits) / R (bits/sec)

• End-end delay

	End-end delay = 2L (bits) / R (bits/sec)
	(Assuming zero propagation delay)

• Store and forward: entire packet must arrive at router before it can be transmitted on next link

• Packet queuing and loss

  • If arrival rate > transmission rate, packets will queue
  • If memory fills up, packets can be dropped
  • Bigger buffer can bring lower packet loss but higher delay+buffer cost

• Two key network-core functios

  • Forwarding
    • Local action: input link -> output link
  • Routing
    • Global action: source -> destinatin
    • Routing algorithms

• Circuit switching

  • End-end resources allocated to, reserved for “call” between source&dest

• Frequency Division Multiplexing (FDM)

• Time Division Multiplexing (TDM)

Packet Switching vs. Circuit Switching

• Packet switching is great for bursty data
  • Resource sharing
  • Simpler, no call setup
• Packet switching can cause excessive congestion
• Combined: Virtual Circuit Packet Switching

Internet Structure: Network of networks

• Hosts connected to internet
• Access ISPs (Internet Service Providers)
  • To ensure every two hosts can send packets to each other, access ISPs must be interconnected

• Tier-1 ISP
  • Sprint, AT&T, NTT
  • National & international coverage
• Content provider network (private network)
  • Google
  • Facebook

Delay and Loss

• Nodal processing
• Queueing delay
• 
  • R: link bandwidth (bps)
  • L: packet length (bits)
  • a: average packet arrival rate
  • Traffic intensity = La / R
  • E(x) = La/R / (1 - La/R)
• Transmission delay
  • L(packet length) / R (link bandwidth)
• Propagation delay
  • d (length of physical link) / s (propagation speed)

	d(nodal) = d(proc) + d(queue) + d(trans) + d(prop)

Example

	Number of hops = M
	Per-hop processing delay = d(proc)
	Link propagation delay = d(prop)
	Packet transmission delay = d(trans)
	Message size = N packets

	End-to-end Delay (ignoring queueing delay)
	= M * d(prop) + N * d(trans) + (M-1) * d(trans) + (M-1) * d(proc)

“Real” Internet delays and routes: traceroute YouTube (macOS)

➜  ~ traceroute youtube.com
traceroute to youtube.com (216.58.197.110), 64 hops max, 52 byte packets
 1  172.24.172.1 (172.24.172.1)  14.211 ms  1.584 ms  1.635 ms
 2  118.140.125.65 (118.140.125.65)  13.122 ms  23.362 ms  7.402 ms
 3  10.30.31.17 (10.30.31.17)  7.024 ms  23.736 ms  54.474 ms
 4  10.28.21.37 (10.28.21.37)  5.924 ms  3.565 ms  2.954 ms
 5  * * *
 6  * 218.188.28.165 (218.188.28.165)  214.507 ms  3.344 ms
 7  108.170.241.65 (108.170.241.65)  3.595 ms
    72.14.222.9 (72.14.222.9)  10.840 ms  3.377 ms
 8  108.170.241.65 (108.170.241.65)  3.156 ms
    216.239.62.59 (216.239.62.59)  3.495 ms
    216.239.62.57 (216.239.62.57)  2.733 ms
 9  216.239.62.59 (216.239.62.59)  4.698 ms
    hkg12s01-in-f14.1e100.net (216.58.197.110)  3.252 ms  4.355 ms

Packet Loss

• Queen (buffer) preceding link in buffer has finite capcity
• Packet arriving to full queue dropped (lost)
• Lost packet may be retransmitted by previous node, end system or not at all

Throughput

• Rate (bits/time) at which bits transferred from sender to receiver
  • Instantaneous: rate at given point in time
  • Average: rate over longer period of time
• Bottleneck link
  • link on end-end path that constrains end-end throughput
  • 
  • Per-connection end-end throughput
    • min(Rc, Rs, R/10)
    • In practice, Rc or Rs is often bottleneck

Why Layering

• Explicit structure allows identification, relationship of complex system’s pieces
• Modularization eases maintenance, updating of system

Internet Protocol Stack

• Application - supporting network applications
  • FTP
  • SMTP
  • HTTP
• Transport - process data transfer
  • TCP
  • UDP
• Network - routing of datagrams from source to destination
  • IP
  • Routing protocol
• Link - data transfer between neighboring network elements
  • Ethernet
  • WiFi
  • PPP
• Physical - bits “on the wire”

ISO/OSI Reference Model (Implemented in Application)

• Presentation
  • Allow applications to interpret meaning of data
• Session
  • Synchronization, checkpoint, recovery of data exchange

Encapsulation

Network Security

• Fields of network security
  • How bad guys can attack computer networks
  • How we can defend networks against attacks
  • How to design architectures that are immune to attacks
• Internet not originally designed with much security in mind

Bad Guys

• Malware
  • From
    • Virus
    • Worm
  • Spyware malware
  • Usage
    • Botnet
    • Spam
    • DDos attacks
• Denial of service (DoS)
  • Make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with fake traffic
  • Procedures
    1. Select target
    2. Break into hosts around the network
    3. Send packets to target from compromised hosts
• Packet interception
  • Packet “sniffing”
  • 
    • Broadcast media (shared ethernet, wireless)
    • Promiscuous network interface reads/records all packets
• Fake identity
  • IP spoofing: send packet with false source address
  • 

Use’s View Of Internet

• Single large (global) network
  • Achieved through software that implements abstractions
• User’s computers all attach directly
• No other structure visible

Internet History

• Early packet-switching principles (1961-1972)
• Internetworking, new and proprietary nets (1972-1980)
• New protocols, a proliferation of networks (1980-1990)
• Commercialization, the Web, new apps (1990’s, 2000’s)
• More new applications, Internet is “everywhere” (2005-Present)