Monday, July 25, 2022

Istio useful commands

Setup multiple primary and multiple cluster network.

1. istioctl proxy-config endpoints

istioctl pc endpoints --context kind-cluster1  helloworld-v1-7b8f6db47c-rw88t.sample


2. istioctl dashboard envoy

 istioctl dashboard envoy helloworld-v2-77f7f4cc45-mrgwv.sample --address=192.168.56.32 --browser=false


3. istioctl dashboard controlz (only against istiod instance)

istioctl dashboard controlz  istiod-7849bf7c66-6prbj.istio-system --address=192.168.56.32 --browser=false


Force ubuntu system to sync date and time for a system

just run the following commands to force the system to sync the date and time. 

sudo timedatectl set-ntp true
sudo timedatectl set-ntp false
sudo timedatectl set-ntp true
Running these 3 commands, then the system will sync your date and time
the correct date and time. 


Ubuntu virtualbox virtual machines can have the system date and time be out sync when the host machine goes on sleep, once the host machine is wake up, the virtual machine's time can be off quite a bit. Run the above command to bring the system date and time to the current.

Friday, July 8, 2022

downstream and upstream in computer networking

In case of Server-Client paradigm, the terms “Upstream” and “Downstream” are used only with respect to the server. So basically "Upstream" means data coming to server (or me), "Downstream" means data leaving server (or me).

In a network, the terms upstream and downstream are used with respect to the position of the devices.

For instance, the flow of packets between three kinds of switches: access, distribution and core switches. The flow of packets from the access switches to the distribution and core switches is upstream. Whereas, from core level switches to access switches, the flow of packets is downstream traffic. With respect to distribution switches, the flow of packets to core switches is upstream traffic while the flow to access switches is downstream traffic.  

So to make this a bit easier, for a giving device (app, or program), if data is coming to the device, then it is upstream. if data is leaving the device, then it is downstream.