Physical Layers and Concepts

Dr. Greg Bernstein

January 29th, 2021

Wired Physical Layers

LAN (Local Area Network)

Ethernet now dominates the wired LAN infrastructure market. You will occasionally see mentions of older technologies such as token ring or specialized high performance computing technologies such as InfinBand, but these are extremely rare in most enterprises.

Ethernet References

Media Types, Speeds and Distances

Just a sample

  • 100BASE‑TX (Fast Ethernet), Cat-5 twisted pair wire, 100 meters
  • 1000BASE‑T (Gig Ethernet), Cat-5 twisted pair wire, 100 meters
  • 10GBASE-SR, 10G over Multi-Mode fiber, 25-400 meters depending on fiber quality
  • 40GbE, 100GbE over parallel multi mode fibers, over WDM single mode fibers. Single mode fibers can achieve distances up to 40km.

WAN: Optical Networks

See Optical slide set.

Advanced Concepts

Layers Again

  • Interoperability points: Physical and logical

  • Management: Fault isolation, Performance monitoring (where did the errors occur)

  • Multiplexing and Switching: Not just one switching layer!!!

Internet Protocol Layers

Internet Protocol Layers

By en:User:Kbrose - Prior Wikipedia artwork by en:User:Cburnett, CC BY-SA 3.0,

10G Ethernet Layers

10G Ethernet Layers

WDM Layers

WDM Layers

The Three-Plane Network Model

In addition to decomposing networks by layer and geography there is the three plane view:

  • Data Plane: This is where the user traffic flows in a network.
  • Control PLane: controls the switching and multiplexing functions in the network. For IP networks this is performed by protocols such as OSPF, BGP, etc…
  • Management Plane: Manages the networks

Control Plane Examples

  • Ethernet: Learning bridge, spanning tree algorithm for loop prevention
  • IP routing: OSPF, RIP, BGP
  • MPLS: enhanced OSPF, RSVP-TE (signaling)
  • WSON/GMPLS: enhanced OSPF, enhanced RSVP-TE

Network Management 1

FCAPS Summary

  • Fault Management
    • the detection, isolation and correction of abnormal operation of the telecommunication network and its environment. Also testing and trouble administration.
  • Configuration Management
    • functions to exercise control over, identify, collect data from and provide data to NEs. Includes: Network Planning and Engineering, Installation, Inventory, Service Planning and Negotiation, Provisioning.

Network Management 2

FCAPS Summary

  • Accounting Management
    • Usage monitoring, generation of call records, billing systems, …
  • Performance Monitoring
    • Evaluates and reports upon the behavior of equipment and the effectiveness of the network or network element, gathers and analyzes statistical data for the purpose of monitoring and correcting the behavior and effectiveness of the network, NEs or other equipment and to aid in planning, provisioning, maintenance and the measurement of QoS.
  • Security Management

Security Implications

Availability Dangers!

Wireless Physical Layers

Low Speed Wireless Examples

WiFi References

WiFi Physical (2.4GHz)

From Wikipedia

2.4GHz Channels

By Rbeede, Liebeskind (original) -, CC BY 3.0,

WiFi Physical Channel Example

Home Router Channels

WiFi Management

From IEEE 802.11 Standard

Management Frames

Getting WiFi Access

  • Access Point (AP) advertises SSID (Beacon Management Frame)
  • Authentication (Authentication Management Frame)
  • Association with AP (Association Management Frame)

Simple Sequence Diagram

From IEEE 802.11 Standard

Association Sequence

Example Associated Stations

Home associated stations

Wireless Security Issues

  • Confidentiality: Anyone can listen to your transmissions!
  • Integrity: Easy to insert transmissions (don’t have to plug in)! “Man in the Middle” attacks…
  • Availability: Jamming (interference) happens all the time! But there are more attacks possible on availability.

Kali Linux Wireless Attack Tools

As of 01/20/2021, includes WiFi, Bluetooth, Zigbee

Airbase-ng, Aircrack-ng, Airdecap-ng and Airdecloak-ng, Aireplay-ng, airgraph-ng, Airmon-ng, Airodump-ng, airodump-ng-oui-updateAirolib-ng, Airserv-ng, Airtun-ng, Asleap, Besside-ng, Bluelog, BlueMaho, Bluepot, BlueRanger, Bluesnarfer, Bully, coWPAtty, crackleeapmd5pass, Easside-ng, Fern Wifi Cracker, FreeRADIUS-WPE, Ghost Phisher, GISKismet, Gqrxgr-scan, hostapd-wpe, ivstools, kalibrate-rtl, KillerBee, Kismet, makeivs-ng, mdk3, mfcuk mfoc, mfterm, Multimon-NG, Packetforge-ngPixieWPS, Pyrit, Reaver, redfang, RTLSDR Scanner, Spooftooph, Tkiptun-ng, Wesside-ng, Wifi Honey, wifiphisher, Wifitap, Wifite, wpaclean

WiFi Phisher 1

From WiFi Phisher documentation

From the victim’s perspective, the attack makes use in three phases:

  1. Victim is being deauthenticated from her access point. Wifiphisher continuously jams all of the target access point’s wifi devices within range by forging Deauthenticate or Disassociate packets to disrupt existing associations.

  2. Victim joins a rogue access point. Wifiphisher sniffs the area and copies the target access point’s settings. It then creates a rogue wireless access point that is modeled by the target. It also sets up a NAT/DHCP server and forwards the right ports. Consequently, because of the jamming, clients will eventually start connecting to the rogue access point. After this phase, the victim is MiTMed.

MiTMed = “Man in the middled”

WiFi Phisher 2

From WiFi Phisher documentation

  1. Victim is being served a realistic specially-customized phishing page. Wifiphisher employs a minimal web server that responds to HTTP & HTTPS requests.

  2. As soon as the victim requests a page from the Internet, wifiphisher will respond with a realistic fake page that asks for credentials or serves malwares. This page will be specifically crafted for the victim. For example, a router config-looking page will contain logos of the victim’s vendor. The tool supports community-built templates for different phishing scenarios.

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