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_switch

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

End-end delay

store_and_forward

	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

circuit_switching

Frequency Division Multiplexing (FDM)

fdm

Time Division Multiplexing (TDM)

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

isp_tiers

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)

packet_delay

	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)

timing_diagram

“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

packet_loss

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

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

user_view_internet 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)

ICOM6012 Topic 2 The Big Picture

ICOM6012 Internet Infrastructure Technologies

Topic 2 The Big Picture

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