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<!doctype html>
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<title>Infrastructure Services - School Of SRE</title>
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<header class="md-header" data-md-component="header">
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School Of SRE
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Infrastructure Services
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</label>
<div class="md-search" data-md-component="search" role="dialog">
<label class="md-search__overlay" for="__search"></label>
<div class="md-search__inner" role="search">
<form class="md-search__form" name="search">
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</form>
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<div class="md-sidebar__scrollwrap">
<div class="md-sidebar__inner">
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<!-- Navigation -->
<nav
class="md-nav md-nav--primary"
aria-label="Navigation"
data-md-level="0"
>
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<ul class="md-nav__list" data-md-scrollfix>
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../.." class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Home
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--section md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
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type="checkbox"
id="__nav_2"
/>
<!-- Toggle to expand nested items -->
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class="md-nav__link"
for="__nav_2"
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tabindex=""
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<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Level 101
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="1"
aria-labelledby="__nav_2_label"
aria-expanded="false"
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<label class="md-nav__title" for="__nav_2">
<span class="md-nav__icon md-icon"></span>
Level 101
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1"
id="__nav_2_1_label"
tabindex="0"
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<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fundamentals Series
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1">
<span class="md-nav__icon md-icon"></span>
Fundamentals Series
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
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<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_1"
/>
<!-- Toggle to expand nested items -->
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class="md-nav__link"
for="__nav_2_1_1"
id="__nav_2_1_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Basics
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_1">
<span class="md-nav__icon md-icon"></span>
Linux Basics
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_basics/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_basics/command_line_basics/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Command Line Basics
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_basics/linux_server_administration/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Server Administration
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_basics/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1_2"
id="__nav_2_1_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Git
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_2">
<span class="md-nav__icon md-icon"></span>
Git
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/git/git-basics/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Git Basics
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/git/branches/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Working With Branches
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/git/github-hooks/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Github and Hooks
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/git/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_1_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_1_3"
id="__nav_2_1_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Networking
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_1_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_1_3">
<span class="md-nav__icon md-icon"></span>
Linux Networking
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/dns/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
DNS
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/udp/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
UDP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/http/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
HTTP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/tcp/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
TCP
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/ipr/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Routing
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/linux_networking/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_2"
id="__nav_2_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Python and Web
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_2">
<span class="md-nav__icon md-icon"></span>
Python and Web
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/python_web/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/python_web/python-concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Some Python Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/python_web/python-web-flask/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Python, Web and Flask
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/python_web/url-shorten-app/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
The URL Shortening App
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/python_web/sre-conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3"
id="__nav_2_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Data
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3">
<span class="md-nav__icon md-icon"></span>
Data
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_1"
id="__nav_2_3_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Relational Databases
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_1">
<span class="md-nav__icon md-icon"></span>
Relational Databases
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/mysql/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
MySQL
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/innodb/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
InnoDB
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/backup_recovery/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Backup and Recovery
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/replication/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
MySQL Replication
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/operations/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Operational Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/select_query/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Select Query
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/query_performance/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Query Performance
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
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<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/lab/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Lab
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_sql/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_2"
id="__nav_2_3_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
NoSQL
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_2">
<span class="md-nav__icon md-icon"></span>
NoSQL
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_nosql/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_nosql/key_concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/databases_nosql/further_reading/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_3"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_3"
id="__nav_2_3_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Message Queue
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_3_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_3">
<span class="md-nav__icon md-icon"></span>
Message Queue
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/messagequeue/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/messagequeue/key_concepts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Key Concepts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/messagequeue/further_reading/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_3_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_3_4"
id="__nav_2_3_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Big Data
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_2_3_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_3_4">
<span class="md-nav__icon md-icon"></span>
Big Data
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/big_data/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/big_data/evolution/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Evolution and Architecture of Hadoop
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/big_data/tasks/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_4"
id="__nav_2_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Systems Design
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_4">
<span class="md-nav__icon md-icon"></span>
Systems Design
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/systems_design/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/systems_design/scalability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scalability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/systems_design/availability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Availability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/systems_design/fault-tolerance/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fault Tolerance
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/systems_design/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_5"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_5"
id="__nav_2_5_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Metrics and Monitoring
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_5_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_5">
<span class="md-nav__icon md-icon"></span>
Metrics and Monitoring
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/command-line_tools/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Command-line Tools
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/third-party_monitoring/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Third-party Monitoring
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/alerts/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Proactive Monitoring with Alerts
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/best_practices/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Best Practices for Monitoring
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/observability/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Observability
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/metrics_and_monitoring/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_2_6"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_2_6"
id="__nav_2_6_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Security
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_2_6_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_2_6">
<span class="md-nav__icon md-icon"></span>
Security
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/fundamentals/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Fundamentals of Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/network_security/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Network Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/threats_attacks_defences/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Threat, Attacks & Defences
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/writing_secure_code/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Writing Secure code
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../../level101/security/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--active md-nav__item--section md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3"
checked
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3"
id="__nav_3_label"
tabindex=""
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Level 102
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="1"
aria-labelledby="__nav_3_label"
aria-expanded="true"
>
<label class="md-nav__title" for="__nav_3">
<span class="md-nav__icon md-icon"></span>
Level 102
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_1"
id="__nav_3_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Intermediate
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_1">
<span class="md-nav__icon md-icon"></span>
Linux Intermediate
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/package_management/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Package Management
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/storage_media/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Storage Media
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/archiving_backup/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Archiving and Backup
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/introvim/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction to Vim
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/bashscripting/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Bash Scripting
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../linux_intermediate/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2"
id="__nav_3_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Linux Advanced
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2">
<span class="md-nav__icon md-icon"></span>
Linux Advanced
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2_1"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2_1"
id="__nav_3_2_1_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Containerization And Orchestration
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_3_2_1_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2_1">
<span class="md-nav__icon md-icon"></span>
Containerization And Orchestration
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../containerization_and_orchestration/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../containerization_and_orchestration/intro_to_containers/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction To Containers
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../containerization_and_orchestration/containerization_with_docker/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Containerization With Docker
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../containerization_and_orchestration/orchestration_with_kubernetes/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Orchestration With Kubernetes
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../containerization_and_orchestration/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_2_2"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_2_2"
id="__nav_3_2_2_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Calls and Signals
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="3"
aria-labelledby="__nav_3_2_2_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_2_2">
<span class="md-nav__icon md-icon"></span>
System Calls and Signals
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_calls_and_signals/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_calls_and_signals/signals/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Signals
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_calls_and_signals/system_calls/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Calls
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_calls_and_signals/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--active md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_3"
checked
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_3"
id="__nav_3_3_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Networking
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_3_label"
aria-expanded="true"
>
<label class="md-nav__title" for="__nav_3_3">
<span class="md-nav__icon md-icon"></span>
Networking
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../security/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Security
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../scale/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scale
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../rtt/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
RTT
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item md-nav__item--active">
<!-- State toggle -->
<input
class="md-nav__toggle md-toggle"
type="checkbox"
id="__toc"
/>
<!-- Hack: see partials/toc.html for more information -->
<!-- Navigation link to table of contents -->
<label class="md-nav__link md-nav__link--active" for="__toc">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Infrastructure Services
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<a
href="./"
class="md-nav__link md-nav__link--active"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Infrastructure Services
</span>
<!-- Navigation link status -->
</a>
<!-- Table of contents -->
<nav class="md-nav md-nav--secondary" aria-label="Table of contents">
<label class="md-nav__title" for="__toc">
<span class="md-nav__icon md-icon"></span>
Table of contents
</label>
<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
<li class="md-nav__item">
<a href="#tor-connectivity" class="md-nav__link">
<span class="md-ellipsis">
ToR connectivity
</span>
</a>
<nav class="md-nav" aria-label="ToR connectivity">
<ul class="md-nav__list">
<li class="md-nav__item">
<a href="#single-tor" class="md-nav__link">
<span class="md-ellipsis">
Single ToR
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#dual-tor" class="md-nav__link">
<span class="md-ellipsis">
Dual ToR
</span>
</a>
<nav class="md-nav" aria-label="Dual ToR">
<ul class="md-nav__list">
<li class="md-nav__item">
<a href="#layer-2" class="md-nav__link">
<span class="md-ellipsis">
Layer 2
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#layer-3" class="md-nav__link">
<span class="md-ellipsis">
Layer 3
</span>
</a>
</li>
</ul>
</nav>
</li>
</ul>
</nav>
</li>
<li class="md-nav__item">
<a href="#anycast" class="md-nav__link">
<span class="md-ellipsis">
Anycast
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#load-balancing" class="md-nav__link">
<span class="md-ellipsis">
Load balancing
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#nat" class="md-nav__link">
<span class="md-ellipsis">
NAT
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#qos" class="md-nav__link">
<span class="md-ellipsis">
QoS
</span>
</a>
</li>
</ul>
</nav>
</li>
<!-- Navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_4"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_4"
id="__nav_3_4_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Design
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_4_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_4">
<span class="md-nav__icon md-icon"></span>
System Design
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/intro/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/large-system-design/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Large System Design
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/scaling/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scaling
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/scaling-beyond-the-datacenter/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Scaling Beyond the Data Center
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/resiliency/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Resiliency
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_design/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_5"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_5"
id="__nav_3_5_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
System Troubleshooting and Performance Improvements
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_5_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_5">
<span class="md-nav__icon md-icon"></span>
System Troubleshooting and Performance Improvements
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/introduction/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Introduction
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/troubleshooting/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Troubleshooting
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/important-tools/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Important Tools
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/performance-improvements/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Performance Improvements
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/troubleshooting-example/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Troubleshooting Example
</span>
<!-- Navigation link status -->
</a>
</li>
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<li class="md-nav__item">
<a href="../../system_troubleshooting_and_performance/conclusion/" class="md-nav__link">
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Conclusion
</span>
<!-- Navigation link status -->
</a>
</li>
</ul>
</nav>
<!-- Pruned navigation item -->
</li>
<!-- Currently active page -->
<!-- Determine classes -->
<!-- Determine active page for paginated views -->
<!-- Navigation item with nested items -->
<!-- Determine all nested items that are index pages -->
<!-- Navigation tabs -->
<!-- Render 1st level items with nested items as sections -->
<!-- Navigation pruning -->
<!-- Nested navigation item -->
<li class="md-nav__item md-nav__item--nested">
<!-- Determine checked and indeterminate state -->
<!-- Active checkbox expands items contained within nested section -->
<input
class="md-nav__toggle md-toggle "
type="checkbox"
id="__nav_3_6"
/>
<!-- Toggle to expand nested items -->
<label
class="md-nav__link"
for="__nav_3_6"
id="__nav_3_6_label"
tabindex="0"
>
<!-- Navigation link icon -->
<!-- Navigation link title -->
<span class="md-ellipsis">
Continuous Integration and Continuous Delivery
</span>
<!-- Navigation link status -->
<span class="md-nav__icon md-icon"></span>
</label>
<!-- Toggle to expand nested items with link to index page -->
<!-- Nested navigation -->
<nav
class="md-nav"
data-md-level="2"
aria-labelledby="__nav_3_6_label"
aria-expanded="false"
>
<label class="md-nav__title" for="__nav_3_6">
<span class="md-nav__icon md-icon"></span>
Continuous Integration and Continuous Delivery
</label>
<ul class="md-nav__list" data-md-scrollfix>
<!-- Nested navigation item -->
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<h1>Infrastructure Services</h1>
<blockquote>
<p><em>Some of the aspects to consider are, whether the underlying data
centre infrastructure supports ToR resiliency, i.e. features like link
bundling (bonds), BGP, support for anycast service, load balancer,
firewall, Quality of Service.</em></p>
</blockquote>
<p>As seen in previous sections, to deploy applications at scale, it will
need certain capabilities to be supported from the infrastructure. This
section will cover different options available, and their suitability.</p>
<h3 id="tor-connectivity">ToR connectivity</h3>
<p>This being one of the most frequent points of failure (considering the scale of deployment), there are different options available to connect the servers to the ToR. We are going to see them in detail below,</p>
<h4 id="single-tor">Single ToR</h4>
<p>This is the simplest of all the options. Where a NIC of the server is
connected to one ToR. The advantage of this approach is, there is a
minimal number of switch ports used, allowing the DC fabric to support
the rapid growth of server infrastructure (Note: Not only the ToR ports
are used efficiently, but the upper switching layer in DC fabric as well,
the port usage will be efficient). On the downside, the servers can be
unreachable if there is an issue with the ToR, link or NIC. This will
impact the stateful apps more, as the existing connections get
abruptly disconnected.</p>
<p><img alt="Graphical user interface, application Description automatically
generated with medium
confidence" src="../media/Single%20ToR.png" /></p>
<p>Fig 4: Single ToR design</p>
<h4 id="dual-tor">Dual ToR</h4>
<p>In this option, each server is connected to two ToR, of the same
cabinet. This can be set up in active/passive mode, thereby providing
resiliency during ToR/link/NIC failures. The resiliency can be achieved
either in layer 2 or in layer 3.</p>
<h5 id="layer-2">Layer 2</h5>
<p>In this case, both the links are bundled together as a <a href="https://en.wikipedia.org/wiki/Link_aggregation">bond</a> on the
server side (with one NIC taking the active role and the other being
passive). On the switch side, these two links are made part of
<a href="https://en.wikipedia.org/wiki/Multi-chassis_link_aggregation_group">multi-chassis lag</a> (similar to bonding, but spread across switches). The
prerequisite here is, both the ToR should be part of the same layer 2
domain. The IP addresses are configured on the bond interface on the
server and SVI on the switch side.</p>
<p><img alt="Diagram Description automatically
generated" src="../media/Dual%20ToR.png" /></p>
<p>Note: In this, the ToR 2 role is only to provide resiliency.</p>
<p>Fig 5: Dual ToR layer 2 setup</p>
<h5 id="layer-3">Layer 3</h5>
<p>In this case, both the links are configured as separate layer 3
interfaces. The resiliency is achieved by setting up a routing protocol
(like BGP). Wherein one link is given higher preference over the other.
In this case, the two ToR's can be set up independently, in layer 3
mode. The servers would need a virtual address, to which the services
have to be bound.</p>
<p><img alt="Diagram Description automatically
generated" src="../media/Dual%20ToR%20BGP.png" /></p>
<p>Note: In this, the ToR 2 role is only to provide resiliency.</p>
<p>Fig 6: Dual ToR layer 3 setup</p>
<p>Though the resiliency is better with dual ToR, the drawback is, the
number of ports being used. As the access port in the ToR doubles up,
the number of ports required in the Spine layer also doubles up, and
this keeps cascading to higher layers.</p>
<table>
<thead>
<tr>
<th>Type</th>
<th>Single ToR</th>
<th>Dual ToR (layer 2)</th>
<th>Dual ToR (layer 3)</th>
</tr>
</thead>
<tbody>
<tr>
<td>Resiliency<sup>1</sup></td>
<td>No<sup>2</sup></td>
<td>Yes</td>
<td>Yes</td>
</tr>
<tr>
<td>Port usage</td>
<td>1:1</td>
<td>1:2</td>
<td>1:2</td>
</tr>
<tr>
<td>Cabling</td>
<td>Less</td>
<td>More</td>
<td>More</td>
</tr>
<tr>
<td>Cost of DC fabric</td>
<td>Low</td>
<td>High</td>
<td>High</td>
</tr>
<tr>
<td>ToR features required</td>
<td>Low</td>
<td>High</td>
<td>Medium</td>
</tr>
</tbody>
</table>
<p><sup>1</sup> Resiliency in terms of ToR/Link/NIC</p>
<p><sup>2</sup> As an alternative, resiliency can be addressed at the application layer.</p>
<p>Along with the above-mentioned ones, an application might need more
capabilities out of the infrastructure to deploy at scale. Some of them
are,</p>
<h3 id="anycast">Anycast</h3>
<p>As seen in the previous section, of deploying at scale, anycast is one
of the means to have services distributed across cabinets and still have
traffic flowing to each one of the servers. To achieve this, two things
are required</p>
<ol>
<li>
<p>Routing protocol between ToR and server (to announce the anycast
address)</p>
</li>
<li>
<p>Support for ECMP (Equal Cost Multi-Path) load balancing in the
infrastructure, to distribute the flows across the cabinets.</p>
</li>
</ol>
<h3 id="load-balancing">Load balancing</h3>
<p>Similar to Anycast, another means to achieve load balancing across
servers (host a particular app), is using load balancers. These could be
implemented in different ways</p>
<ol>
<li>
<p>Hardware load balancers: A LB device is placed inline of the traffic
flow, and looks at the layer 3 and layer 4 information in an incoming
packet. Then determine the set of real hosts, to which the connections
are to be redirected. As covered in the <a href="https://linkedin.github.io/school-of-sre/level102/networking/scale/#load-balancer">Scale</a> topic, these load balancers can be set up in two ways,</p>
<ul>
<li>
<p>Single-arm mode: In this mode, the load balancer handles only the
incoming requests to the VIP. The response from the server goes directly
to the clients. There are two ways to implement this,</p>
<ul>
<li>
<p>L2 DSR: Where the load balancer and the real servers remain in the
same VLAN. Upon getting an incoming request, the load balancer
identifies the real server to redirect the request and then modifies the
destination mac address of that Ethernet frame. Upon processing this
packet, the real server responds directly to the client.</p>
</li>
<li>
<p><a href="https://github.com/yahoo/l3dsr">L3 DSR</a>: In this case, the load balancer and real servers need not be
in the same VLAN (does away with layer 2 complexities like running STP,
managing wider broadcast domain, etc). Upon incoming request, the load
balancer redirects to the real server, by modifying the destination IP
address of the packet. Along with this, the DSCP value of the packet is
set to a predefined value (mapped for that VIP). Upon receipt of this
packet, the real server uses the DSCP value to determine the loopback
address (VIP address). The response again goes directly to the client.</p>
</li>
</ul>
</li>
<li>
<p>Two arm mode: In this case, the load balancer is in line for incoming
and outgoing traffic.</p>
</li>
</ul>
</li>
<li>
<p>DNS based load balancer: Here the DNS servers keep a check of the
health of the real servers and resolve the domain in such a way that the
client can connect to different servers in that cluster. This part was
explained in detail in the deployment at <a href="https://linkedin.github.io/school-of-sre/level102/networking/scale/#dns-based-load-balancing">scale</a> section.</p>
</li>
<li>
<p>IPVS based load balancing: This is another means, where an IPVS
server presents itself as the service endpoint to the clients. Upon
incoming request, the IPVS directs the request to the real servers. The
IPVS can be set up to do health for the real servers.</p>
</li>
</ol>
<h3 id="nat">NAT</h3>
<p>Network Address Translation (NAT) will be required for hosts that need
to connect to destinations on the Internet, but don't want to expose
their configured NIC address. In this case, the address (of the internal
server) is translated to a public address by a firewall. Few examples of
this are proxy servers, mail servers, etc.</p>
<h3 id="qos">QoS</h3>
<p>Quality of Service is a means to provide, differentiate treatment to few packets
over others. These could provide priority in forwarding queues, or
bandwidth reservations. In the data centre scenario, depending upon the
bandwidth subscription ratio, the need for QoS varies,</p>
<ol>
<li>
<p>1:1 bandwidth subscription ratio: In this case, the server to ToR
connectivity (all servers in that cabinet) bandwidth should be
equivalent to the ToR to Spine switch connectivity. Similarly for the
upper layers as well. In this design, congestion on a link is not going
to happen, as enough bandwidth will always be available. In this case,
the only difference QoS can bring, it provides priority treatment for
certain packets in the forwarding queue. Note: Packet buffering happens,
when the packet moves between ports of different speeds, like 100Gbps,
10Gbps.</p>
</li>
<li>
<p>Oversubscribed network: In this case, not all layers maintain a
bandwidth subscription ratio, for example, the ToR uplink may be of
lower bandwidth, compared to ToR to Server bandwidth (This is sometimes
referred to as oversubscription ratio). In this case, there is a
possibility of congestion. Here QoS might be required, to give priority
as well as bandwidth reservation, for certain types of traffic flows.</p>
</li>
</ol>
</article>
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