Monday, December 24, 2007

Calculating Frame-Relay map-class parameters

Have you struggle to understand what seems like black magic behind the calculation of the parameters of a frame-relay map? Well, I did for a long time. Frame-relay is one of those technologies that isn't going to disappear anytime soon. So if you are a consultant you will find yourself implementing QoS over frame-relay.
Now Cisco provides several ways of doing QoS over Frame-Relay but here I'm going to cover the map-class and its basic parameters.


Unlike many other documents I'm not going to explain all the theory behind this parameters, I'm going to give you a simple recipe which I use. There are mostly two types of map-class you are going to find deploying. Those to shape data traffic and those to shape VoIP traffic. Anything else is a mix of any of those two. (Most of the time... there is always those exception to the rule)

Since CIR is what you providers tell you based in what you bought, for this discussion I will assume a line of 768K with a CIR of 512K.

You will find that the documents out there always mention the Tc value and that all the calculations are based on the Tc value you are using, etcetera. Well, you know what? It is true, BUT you can not set this parameter. It is router auto-calculated value based on your other parameters. You have to "indirectly" modify it. So, this was the first issue that I always struggle with and never understood well.

It is simple, the default Tc = 1s and you can forget about everything else and remember this: The industry "best practices" define Tc = 125ms for data traffic and Tc = 10ms for VoIP traffic.

How they get there? Long story and I promised not to do all the calculations. You only need to remember this. They recommend to have 8 time-slots for DATA and for VoIP 100 time-slots. So, that's how you obtain:

Data: 1s / 8 = 0.125 s = 125 ms
VoIP: 1s / 100 = 0.010 = 10ms

The easiest way to calculate the values for a frame-relay map class for DATA:

CIR = 512000
Bc = CIR / 8 = 512000 / 8 = 64000
Be = (Available Bandwith - CIR) / 8 = (768000 - 512000) / 8 = 32000

Note: You will only need to calculate the Be if your CIR is less that the provisioning of the line and you what to have the "extra burst". Otherwise, don't define that parameter.

To calculate the sames parameters for a frame-relay map for VoIP:

CIR = 512000
Bc = CIR / 100 = 5120
Be = (Available Bandwidth - CIR) / 100 = (768000 - 512000) / 100 = 2560

Note: You will only need to calculate the Be if your CIR is less that the provisioning of the line and you what to have the "extra burst". Otherwise, don't define that parameter.

Now, there are some additional parameters that are defined for VoIP, I will only cover the "fragmentation" or "fragment size". This is not necessarily how it is explained, but the calculation works for me:

frame-relay fragment = Bc / 8 = 5120 / 8 = 640

Finally make sure you give VoIP RTP traffic the priority you want. In this case, lets say that I want to give it priority over the full CIR. I will then have an entry like this:

frame-relay ip rtp priority 16384 16383 512

So the final map-class will look like:

!
map-class frame-relay DATA_768K_CIR_512K
frame-relay cir 512000
frame-relay bc 64000
frame-relay be 32000
!
!
map-class frame-relay VoIP_768K_CIR_512K
frame-relay cir 512000
frame-relay bc 5120
frame-relay be 2560
frame-relay fragment 640
frame-relay ip rtp priority 16384 18383 512
!

Finally, apply it to our interface:

!
int Serial0/0
encapsulation frame-relay
no frame-relay inverse-arp
frame-relay traffic-shaping !Need to be activated at physical interface level
!
!
int Serial 0/0.100
ip address 192.168.100.2 255.255.255.0
frame-relay class DATA_768K_CIR_512K
frame-relay interface-dlci 100
!

And that is it. For more information visit:


VoIP over Frame Relay with Quality of Service (Fragmentation, Traffic Shaping, LLQ / IP RTP Priority)

Hope you find this useful.

32 comments:

  1. This is good article for practical approach but there is just one confusion that why you have used bc=CIR/8 for data and bc=CIR/100 while exactly it is BC=cir*tc/1000, but again if it is your best practice and if practically gives nearly accurate value then I would for for this as it is easy to remember. But for exam for which I am preparing I think BC=cir*tc/1000 is good for me. Just sharing thought with you.. Zaheer

    ReplyDelete
  2. This article is very interesting and I really like your thoughts in writing this article is extraordinary.
    raja poker

    ReplyDelete
  3. You managed to hit the nail upon the top and also defined out the whole thing without having side effect , people could take a signal. Will likely be back to get more. Thanks
    Tangki Panel
    Tangki Fiberglass
    Jual Septic Tank
    Tangki Kimia
    Jual Talang Fiber
    Jual Rotameter
    jual mesin ro
    Jual Botol Plastik Agro

    Jual Botol Plastik Murah

    ReplyDelete
  4. I hope to hear more updates from you, this is what I want to find.
    instagram viewer

    ReplyDelete
  5. Hey thanks for sharing all this information learned a lot. Do check below:
    buy logo

    ReplyDelete
  6. You are doing a great job, and up to date with technology of your site. Ill find it as an inspiration to my current project. Thanks เว็บเล่นบาคาร่า

    ReplyDelete
  7. Nice Blog...Thanks for sharing with us...and i have some information about The Botanika and it is a new residential project located in Gachibowli, Hyderabad. This project offers 3 BHK Luxury Apartments in Affordable Prices. Contact Us@ 98492 05577

    The Botanika Hyderabad
    The Botanika Gachibowli

    ReplyDelete
  8. I enjoyed reading your post.You make so many great points here that I read your article a couple of times.
    Asrithas Jewels County
    Asrithas Jewels County Hyderabad

    ReplyDelete
  9. It’s amazing and helpful article for all sort of readers. please share more article. you must read if you are live in Australia I really appreciate to you. I also rerecommended to you lean too...
    learn more
    learn more

    ReplyDelete
  10. This content material is written very well. Your use of formatting when making your factors makes your observations very clear and clean to apprehend. Thank you.


    law dissertation Writing Service

    ReplyDelete
  11. Great post. I was checking constantly this blog and I'm

    impressed! Extremely helpful info specially the last part :

    ) I care for such information much. I was seeking this certain info for

    a very long time. Thank you and good luck.
    Acts 1:8 Foundation

    ReplyDelete
  12. Great post and great site. Guys, very interesting recipes and a large selection of kitchen utensils.https://kitchenbackground.com/

    ReplyDelete
  13. Over 80% say that playing is legitimate 온라인 카지노 and casinos are okay. You can, nevertheless, bet on those races from 23 casinos and county fairs across the state, or even from residence. People exterior the state can bet on races taking place in California as nicely. It’s the only form of sports betting at present allowed within the Golden State.

    ReplyDelete
  14. Great post. I was checking constantly this blog and I'm impressed! Thanks for sharing... This is Very Nice One And Gives In depth Information... mortgage raising capacity report

    ReplyDelete
  15. Calculating Frame-Relay map-class parameters involves defining crucial settings for efficient data transmission. Precise configuration ensures optimal network performance and streamlined communication. ipad price in bd






    ReplyDelete
  16. I really like your blog thanks for sharing...and i have some information about
    Health tips

    ReplyDelete
  17. I'm always looking for new fashion trends to try out. These suggestions are great and very inspiring!
    YouTube

    ReplyDelete
  18. "I never considered the psychological effects of color in interior design until I read this. Now I'm eager to repaint my bedroom with soothing tones and create a relaxing sanctuary."live score

    ReplyDelete
  19. ActiveLife is my personal fitness companion. The app's diverse workout routines, progress tracking, and personalized recommendations keep me motivated and on track to meet my fitness goals. Staying active has never been this enjoyable!"

    ReplyDelete
  20. Your dedication and hard work are truly inspiring. Thank you for consistently going above and beyond."Rajshahi University

    ReplyDelete
  21. In the ever-evolving world of mobile technology, Vivo has emerged as a prominent player, consistently pushing the boundaries of innovation and design. Founded in 2009, this Chinese smartphone manufacturer has quickly risen to prominence, captivating consumers with its commitment to excellence. This article explores the fascinating journey of Vivo mobile phones and highlights their significant contributions to the smartphone industry.

    ReplyDelete
  22. This comment has been removed by the author.

    ReplyDelete
  23. This comment has been removed by the author.

    ReplyDelete
  24. n the ever-evolving world of mobile technology, Vivo has emerged as a prominent player, consistently pushing the boundaries of innovation and design. mobile price in bd

    ReplyDelete