Transcript All About Home Wireless Routers

Brian Hixenbaugh
Network Managment
My Home Network
My Plan…
 N.A.S. (1 TB External Hard Drive)
 Connects to Router via Ethernet (Has IP Address)
 Stores movies, television shows, etc.
 Laptop Connected to TV (Downstairs)
 Wirelessly stream content from N.A.S. or Internet
 Display on television
 Roommate’s Laptop (iPhone, etc.)
 Independently use Internet or N.A.S. as well
It Works! (Almost)
 Need to Implement QoS (Quality of Service)
 Router Inspects Packets – Prioritizes Video, VoIP
 Low Priority – P2P
 Improve Radio Performance
 Increase TX power, Increase Beacon Interval
 Expensive Commercial Routers Offer These Features
 Cheap home routers can offer these features as well with
replacement software!
Embedded Systems
 A Router is a “Mini” Computer with:
 CPU
 RAM
 Hard Drive (Flash Chip)
 Open Source Software Can Replace Factory Software to
Provide More Features
 OpenWRT
 Tomato
 DD-WRT
Netgear WGR614
DD-WRT
“Flashing” New Software
 Similar to a PC
 Boot program (CFE)
 Kernal (linux!)
 Software (dd-wrt)
 Upload via Router’s Web GUI (Ethernet)
 Software not always compatible with all makes & models
of routers
 Flash memory locations can be different
 There can be problems!
Bricked
Fix a Brick with JTAG
 Joint Test Action Group or Boundary-Scan
 IEEE Standard for communicating with embedded
systems
 Allows issuing commands directly to Processor
 Allows directly programming Flash Memory
 Allows a PC to Communicate for Debugging
 Requires parallel port on PC, special interface device,
and communication software
Common Firmware Environment
 CFE contains information for Ethernet (MAC addr.)
 Also contains information to boot Kernal
 If damaged, must be replaced by JTAG
 CFE is small (~128k) but JTAG is slow – can take 5-10
minutes to upload
 Kernal & software are much larger (2-3MB) not practical
to send via JTAG
 Once CFE is uploaded and running, remaining software
can be quickly flashed via Ethernet using TFTP (Trivial
File Transfer Protocol)
No Happy Ending
 Could not successfully
reload factory software
 Possible hardware
problems (bad flash
chip, CPU)
 Still a Brick!