# QoS, Load Balancing and Policy Route (iproute2, traffic control and netlink socket)
###### tags: `linux` `QoS` `iproute2` `traffic control` `tc` `ip route` `policy route` `load balancing`
Author: WhoAmI
Date: 20220728
Copyright: CC BY-NC-SA

:::success
[財團法人台灣兒童暨家庭扶助基金會](https://https:www.ccf.org.tw/)

:::


這些是運用 [netlink - communication between kernel and user space(AF_NETLINK)](https://man7.org/linux/man-pages/man7/netlink.7.html)

netlink socket設計想法: 把 Linux user space 與 kernel space 看成 client/server 架構

例如 您可透過 AF_NETLINK 檢查 route 狀態, e.g., PPPoE

:::info
這裡其實真正困難的是 決策問題與優先權的規劃, 使用者命令並不多!

困難的是: 由於 進入的使用者是隨機現象, Detection, Estimation, QoS decision, and Priority 的規劃!

例如 當有 QoS 需求時, 檢測最 "忙" 的 server 然後切換至其他 server 其實不一定是最好的選擇! 有時反而會更嚴重! 甚至不穩定!
:::

實務上請盡可能用
:::info
ip route ...代替 route

ip addr ... 代替 ifconfig

QoS:

tc (traffic control)
:::

**運作原理基本概念~Queueing Networks**









[IPROUTE2 Utility Suite Howto](https://www.policyrouting.org/iproute2.doc.html)

[Linux Advanced Routing Tutorial
by Michal Ludvig on September 12, 2013 ](https:////www.linuxjournal.com/content/linux-advanced-routing-tutorial)

**了解 Bridge! 其實這也很重要!**

[Linux Bridge
Linux BRIDGE-STP-HOWTO: About The Linux Modular Bridge And STP](https://www.tldp.org/HOWTO/BRIDGE-STP-HOWTO/set-up-the-bridge.html)

iptables -A FORWARD -p tcp --syn -m limit --limit 1/s -j ACCEPT

[Iptables Tutorial – Securing Ubuntu VPS with Linux Firewall](https://www.hostinger.com/tutorials/iptables-tutorial)