Sunday, January 29, 2012

FRF.12 Link Fragmentation and Interleaving calculation

Assuming we want to configure FRF.12 with interleaving and fragmentation delay of 10ms on a 768Kbps link:

Delay = Frame size (bits) / Link Bandwidth (bps)
0.01s = Frame size (bits) / 768,000 bps
Frame size = 7680 bits = 960 bytes

This is the configuration example extracted from the AutoQoS applied on the frame relay sub-interface

map-class frame-relay AutoQoS-FR-Se0/0/0:1-202
  frame-relay cir 768000
  frame-relay bc 7680
  frame-relay be 0
  frame-relay mincir 768000
  frame-relay fragment 960
  service-policy output AutoQoS-Policy-Trust

SRR queue - sharing and shaping on 3750

On 3750, both ingress and egress queue are serviced by SRR queue.  Here are a summary on SRR queue sharing and shaping:

1. You can configure sharing or shaping for egress queue, however for ingress you can only configure sharing.

2. In shaped mode, the egress queues are guaranteed a percentage of the bandwidth, and they are rate-limited to that amount. Shaped traffic does not use more than the allocated bandwidth even if the link is idle.

3. With shaping, the inverse absolute value of each weight is used to compute the bandwidth available for the queues.

Example: "srr-queue bandwidth shape 4 0 0 0", which means 1/4 of the interface bandwidth is assigned to queue 1.  If the link is a FE interface, around 25Mbps is allocated.  Even if the link is idle, queue 1 can't use more than 25Mbps bandwidth in this case.

4. In shared mode, the queues share the bandwidth among them according to the configured weights. The bandwidth is guaranteed at this level but not limited to it. For example, if a queue is empty and no longer requires a share of the link, the remaining queues can expand into the unused bandwidth and share it among them.

5. With sharing, the ratio of the weights controls the frequency of dequeuing.

Example: "srr-queue bandwidth share 30 40 25 5", the sum is 30 + 40 + 25 + 5 = 100 (better to reference to 100 for ease of calculation). The relative rate are 30/100, 40/100, 25/100 and 5/100

6. Shaping and sharing is configured per interface. Each interface can be uniquely configured.

7. You can mix shared and shaped on the same interface.

interface GigabitEthernet 1/0/1
srr-queue bandwidth share 1 30 40 30
srr-queue bandwidth shape 5 0 0 0

The interface bandwidth is 1000Mbps, queue 1 will get 1/5 = 200 Mbps. Queue 2, 3 and 4 will share the remaining 800Mbps.

Queue 2 = 800Mbps x 30% = 240Mbps
Queue 3 = 800Mbps x 40% = 320Mbps
Queue 4 = 800Mbps x 30% = 240Mbps

8. When you type "priority-queue out", you will turn queue 1 into PQ, it will ignore shared and shaped weight in the calculation. It means the PQ has 100% bandwidth when it needs, therefore other shaped queue may starve.

Saturday, January 28, 2012

Changing Background Image for CME IP phones

To change the background image of IP phone for CME is quite similar to UCM, I am using a 7965 as an example to illustrate how to get it done.

7965 resolution
Actual Background Image - 320x212
Image Thumbnail - 80x53

Create 2 images based on above resolution.

1. Create directory on CME router
mkdir Desktops
cd Desktops
mkdir 320x212x16
cd 320x212x16

2. Compose a List.xml file, here the example:
Then copy the List.xml, voice-large.png and voice-small.png to flash:Desktops/320x212x16/

3. allow tftp-server file access on CME
tftp-server flash:Desktops/320x212x16/List.xml
tftp-server flash:Desktops/320x212x16/voice-large.png
tftp-server flash:Desktops/320x212x16/voice-small.png

Check out the phone User Preference > Background image, and you will see the thumbnail image.  Choose it and you can change to the new background image!

For UCM, you can use the JQ Phone iPhone app to use the iPhone image to IP phone background!  Check it out here:

Factory Reset Cisco Unity Express

One of the thing that you did most in lab practice is reset the scene.  This is the way how we reset the CUE module to factory default.

Saturday, January 14, 2012

Downgrade to IE 6

I have an application that can only run on IE 6, and I have downgraded my machines with IE 7 and IE 8 back to IE 6.  Here is how I did it on my old XP boxes:

1. Run %windir%\ie7\spuninst\spuninst.exe
2. Reboot your machine
3. Then launch your IE 6 with the command iexplore.exe

Good luck!