Tidy up

docs/lectures/acn/12_naming.md

@@ -1,6 +1,6 @@
 # Naming
 
-IPs are not human readable.
+IPs are not human-readable.
 
 Not always the appropriate granularity
 
@@ -10,11 +10,11 @@ Not always the appropriate granularity
 A file maps names to addresses
 
 - Unix & Linux
-  - `/etc/hosts`
+    - `/etc/hosts`
 - Windows
-  - `C:\Windows\System32\drivers\etc\hosts`
+    - `C:\Windows\System32\drivers\etc\hosts`
 
-These are simple but neither automatic or scalable which led to **DNS**.
+These are simple but neither automatic nor scalable, which led to **DNS**.
 
 - Was initially `RFC882`
 - Now is `RFC1035, 1987`
@@ -22,24 +22,24 @@ These are simple but neither automatic or scalable which led to **DNS**.
 DNS is a consistent namespace
 
 - No reference to addresses, routes etc
-- Is hierarchical, distributed & cache
-  - All of which to help with scalability
+- Is hierarchical, distributed and cached
+    - All of which help with scalability
 - **Federated** - sources control trade-off
-  - This just means DNS are worldwide
-- **Flexible** - many record
+    - This just means DNS is worldwide
+- **Flexible** - many records
 - Simple client-server name resolution protocol
 
 #### Components
 
 - *Domain name space* and *resource records*
-  - Tree structured name space
-  - Data associated with names
+    - Tree-structured name space
+    - Data associated with names
 - *Name server*
-  - Contains records for a sub tree
-  - May cache information about any part of the tree
+    - Contains records for a subtree
+    - May cache information about any part of the tree
 - Resolver
-  - Extract information from tree upon client requests
-  - `gethostbyname()`
+    - Extracts information from the tree upon client requests
+    - `gethostbyname()`
 
 ![img](img/aa.png)
 
@@ -48,26 +48,26 @@ DNS is a consistent namespace
 - Ultimate authority with the US Dept. of commerce (NITA)
 - Managed by IANA, operated by ICANN, maintained by Verisign
 - Started with only thirteen root server clusters
-  - Now much more
-- Top level Domains, TLDs
-  - Operated by registrars, delegated by ICANN
+    - Now many more
+- Top-level domains, TLDs
+    - Operated by registrars, delegated by ICANN
 - Delegate zones to other registrars
-  - and so on down the hierarchy
-- Eventually customer rents a name - their **zone**
-  - Registrar installs appropriate *resource records*
-  - Associated with names within the zone
+    - and so on down the hierarchy
+- Eventually, a customer rents a name - their **zone**
+    - Registrar installs appropriate *resource records*
+    - Associated with names within the zone
 
 #### Query
 
 - Query generated by resolver
-  - e.g. call to `gethostbyname()`, `gethostbyaddr()`
+    - e.g. call to `gethostbyname()`, `gethostbyaddr()`
 - Carried in single UDP/53 packet
-  - Or more rarely TCP/53 in case of truncation
-  - UDP is not smart and therefore does not follow traffic routing (it is selfish)
-    - It is beneficial for the internet as a whole to use UDP sometimes
+    - Or more rarely TCP/53 in case of truncation
+    - UDP is not smart and therefore does not follow traffic routing (it is selfish)
+        - It is beneficial for the internet as a whole to use UDP sometimes
 - Header followed by question
-  - ID, Q/R, opcode, AA/TC/RD/RA, response code, counts
-  - Query type, query class, query name
+    - ID, Q/R, opcode, AA/TC/RD/RA, response code, counts
+    - Query type, query class, query name
 
 Response consists of three RRsets following the header and question
 
@@ -113,27 +113,27 @@ nott.ac.uk.	3600	IN	MX	2 mx192.emailfiltering.com.
 nott.ac.uk	3600	IN	MX	3 mx193.emailfiltering.com.
 ```
 
-What happens when the resolver queries a server that doesn't know the answer? two solutions:
+What happens when the resolver queries a server that doesn't know the answer? There are two solutions:
 
 1. **Iterative** (required)
-   - Server responds indicating who to ask next
-   - This method is slower and more difficult to retrieve an answer
+    - Server responds indicating who to ask next
+    - This method is slower and more difficult to retrieve an answer
 1. **Recursive** (optional)
-   - Server generates a new query to the next server
+    - Server generates a new query to the next server
 
 ![img](img/ab.png)
 
 #### Load Balancing
 
-DNS may have multiple servers, when a query comes various algorithms can be used to choose the best one, this can be geographical location.
+DNS may have multiple servers. When a query arrives, various algorithms can be used to choose the best one, for example, based on geographical location.
 
 #### Operational & Security Issues
 
 - Usually need primary and secondary servers
-  - Separate IP netblocks, physical networks - more robust
-  - DNS is a *very* common single point of failure
+    - Separate IP netblocks, physical networks - more robust
+    - DNS is a *very* common single point of failure
 - Cache poisoning
-  - Caching and soft-state means bad data propagates and can persist for some time
-  - Even if through simple mistakes (or of course malicious attacks)
+    - Caching and soft-state means bad data propagates and can persist for some time
+    - Even if through simple mistakes (or of course malicious attacks)
 - Man-in-the-middle attacks
-  - Can happen with both iterative & recursive queries
+    - Can happen with both iterative & recursive queries