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Why network engineers need to know Linux

Unix is something that I learned long long time ago while Slackware was ruling the world of Linux. At that time I had no idea how much I did not know about it and since then the things went crazy and the Unix Universe enlarged to an unimaginable size.

Becuse today more and more devices are based on Linux I guess it would be bad taste to say you do not know Unix and that goes especially for  Linux. From phones and tablets to robots and routers many many  other things are powered by Linux these days.

This article came out of my frustration with not knowing what exactly I am doing and who I am dealing with when working with various network appliances, especially when it comes to hacking these appliances. Here are just a couple of then that I have been dealing with for the last couple of months:

  • Cisco ASA appliances
  • Alteon Load balancers
  • F5 load balancers
  • OpenVswitch
  • Checkpoint Firewall
  • OpenFlow and Openvswitch
  • Linkys routers usig dd-wrt

The list is quite long and all the above have one thing in common: The Linux Kernel and its network related features. Today’s kernel capabilities have evolved to the point where the Linux kernel is not only a money and time saving solution but it also opens a full range of options when it comes to building network appliances around it

Long story short, my target for these articles is to clarify and put in good order the following:

  • differences between various flavours of Unix/Linux and how they evolved
  • next I will focus on the Linux kernel
  • a list of network appliances that I deal with on a daily basis and what kernel they are based on
  • the kernel networking concepts
  • network emulators and how to use them
  • virtualisation with Linux

I do not intend explore the above to their full extent but just enough to give me the confidence that I know exactly what can be done and what can not be done specific situation.


The Linux Kernel map

I have recently started to develop an interest for virtual networking as this is becoming an important step in a “Cloud” incarnation. Here is just a link for now


I am currently studying the Open vSwitch architecure and features. Next I will continue with a short look at VMware vSwitch and Nexus 1000. The final leg of this virtual trip will be the “virtual appliances” from vendors like F5, Alteon, Checkpoint and so on.

Free AAA: Tacacs+ vs Radius

Here is a short article that will help and guide you in case you have to select one of these two protocols for controlling the access to your devices. The first thing you have to bear in mind is that while Tacacs is a propietary protocol (Cisco) Radius is an open standard protocol and it is natively supported by many applications and network devices. Plese see below a comparision table between the two protocols:

A quick look at traffic generators

Due to a change in priorities for the client I am working with I will have to postpone studying BGP (actually resuming this) and to start learning QoS and to add some Voice to my skills. This is a great opportunity and I am very happy that I can learn this.
Any serious QoS learning will involve testing and I don't think that you can seriously do that without using a traffic generator. So here is the list with traffic generators that I am currently evaluating and my opinions about each of them:
  1. TTCP
  2. IxChariot
  3. JPerf/Iperf
  4. Pagent
  5. Packet Builder
  6. Scapy
  7. Ostinato
  8. Mtools
  9. MGEN
  10. Rude/Crude
  11. UDPgen
  12. UDP Generator
  13. Network Traffic Generator
  14. MxTraf
  15. NTGen
  16. Netperf
  17. Traffic Generator Tool
  18. TfGen
  19. Packet Shell
  20. Real-Time Voice Traffic Generator
  21. Self Similar Traffic Generator
  22. PacGen packet forger
  23. IPGen packet forger
  24. IP-Packet packet forger
  25. GenSyn
  26. Netspec Traffic emulator
  27. Surge Traffic emulator
  28. Poisson Traffic Generator
  29. FTP traffic generator
  30. Brawny and Rough Udp Traffic Engine
  31. Jugi's Traffic Generator (jtg)
  32. TrafGen
  33. SPAK, Packet Generator
  34. TTCP, Test TCP
  35. PIM-SM, Protocol Independent Multicast Packet Generator
  36. KUTE-- Kernel-based Traffic Engine
  37. GEIST - Generator of E-commerce and Internet server Traffic

Commercial Tools

LANdecoder32T Traffic Generator  
LANTraffic V2 and IP Traffic Test & Measure  
Traffic Generator for Wide Area Networks  
Candela Technologies LANforge-FIRE Network Traffic Generator Testing Specific Protocols  
ProvaGEN 3.0  
Internetworking Test Traffic Generation Programs  
Omnicor Hardware IP traffic generators    
Omnicor Software IP traffic generators  
Skaion's Traffic Generation System (TGS)