From c74fc01d2eeaff12cc9e7b2ed7d0c1a7ebb45887 Mon Sep 17 00:00:00 2001
From: Tyler Perkins <tperki17@kent.edu>
Date: Mon, 25 Apr 2022 12:30:01 -0400
Subject: [PATCH] Update for 25-04-22 12:30

---
 tech/DHT.wiki        | 38 ++++++++++++++++++++++++++++++++++++++
 tech/algorithms.wiki |  1 +
 2 files changed, 39 insertions(+)
 create mode 100644 tech/DHT.wiki

diff --git a/tech/DHT.wiki b/tech/DHT.wiki
new file mode 100644
index 0000000..b48c0f6
--- /dev/null
+++ b/tech/DHT.wiki
@@ -0,0 +1,38 @@
+= DHT =
+
+A DHT or Distributed Hash Table is a distributed system that provides a look up
+service, similar to that of a [[hash_table]]. The difference however, is the
+distributed, self organizing nature of such a datastructure. The keys are
+distributed in such a manner that any disruption of nodes causes minimal
+disruption to the availability of the data.
+
+DHTs are used in cooperative web caching, distributed file systems, domain name
+services, instant messaging, and peer-to-peer file sharing. DHTs are used by
+BitTorrent, Freenet, and [[IPFS]].
+
+== Structure ==
+
+A DHT is made up of several components
+
+* Abstract keyspace
+  * IE all 160bit strings
+  * Partitioned across all participating nodes
+* Overlay network
+  * TCP/IP protocol to allow nodes to find each other
+  * Allows node to query network for any vlaue
+
+=== Insertion ===
+
+Some _filename_ and _data_ exist. A SHA-1 hash is taken of _filename_ and
+produces a key, _k_, in the specified keyspace. The message `put(k,data)` is
+sent to any node in the network, and is forwarded till the node responsible for
+key _k_ is found, and then that node stores the _data_ and _key_.
+
+=== Retrieval ===
+
+A node wants to find some _filename_. They take the SHA-1 hash of _filename_
+and produce some key, _k_. `get(k)` is sent to any other node, and the message
+is propogated through the network till the node responsible for _k_ is found,
+and replies with _data_.
+
+=== Keyspace Partitioning ===
diff --git a/tech/algorithms.wiki b/tech/algorithms.wiki
index 5d6a673..84b8691 100644
--- a/tech/algorithms.wiki
+++ b/tech/algorithms.wiki
@@ -11,6 +11,7 @@ Different ways to store and operate on data, with differing efficiency
 * [[queue|Queue]]
 * [[skip_list|Skip list]]
 * [[hash_table|Hash Table]]
+* [[DHT|Distributed Hash Table]]
 
 == Non sequential Data Structures ==