obonaventure · gregbo · Dec 28, 2021 · Dec 28, 2021 · Dec 28, 2021 · Dec 29, 2021
diff --git a/book/application/dns.rst b/book/application/dns.rst
@@ -12,7 +12,7 @@ Because names are at a higher level than addresses, they allow (both in the exam
 
 .. index:: Network Information Center, hosts.txt
 
-The first solution that allowed applications to use names was the :term:`hosts.txt` file. This file is similar to the symbol table found in compiled code. It contains the mapping between the name of each Internet host and its associated IP address [#fhosts]_. It was maintained by SRI International that coordinated the Network Information Center (NIC). When a new host was connected to the network, the system administrator had to register its name and IP address at the NIC. The NIC updated the :term:`hosts.txt` file on its server. All Internet hosts regularly retrieved the updated :term:`hosts.txt` file from the server maintained by SRI_. This file was stored at a well-known location on each Internet host (see :rfc:`952`) and networked applications could use it to find the IP address corresponding to a name. 
+The first solution that allowed applications to use names was the :term:`hosts.txt` file. This file is similar to the symbol table found in compiled code. It contains the mapping between the name of each Internet host and its associated IP address [#fhosts]_. It was maintained by the SRI International Network Information Center (NIC). When a new host was connected to the network, the system administrator had to register its name and IP address at the NIC. The NIC updated the :term:`hosts.txt` file on its server. All Internet hosts regularly retrieved the updated :term:`hosts.txt` file from the server maintained by SRI_. This file was stored at a well-known location on each Internet host (see :rfc:`952`) and networked applications could use it to find the IP address corresponding to a name. 
 
 A :term:`hosts.txt` file can be used when there are up to a few hundred hosts on the network. However, it is clearly not suitable for a network containing thousands or millions of hosts. A key issue in a large network is to define a suitable naming scheme. The ARPANet initially used a flat naming space, i.e. each host was assigned a unique name. To limit collisions between names, these names usually contained the name of the institution and a suffix to identify the host inside the institution (a kind of poor man's hierarchical naming scheme). On the ARPANet few institutions had several hosts connected to the network. 
 
@@ -122,7 +122,7 @@ An important point to note regarding the Domain Name System is its extensibility
 .. rubric:: Footnotes
 
 
-.. [#fhosts] The :term:`hosts.txt` file is not maintained anymore. A historical snapshot retrieved on April 15th, 1984 is available from http://ftp.univie.ac.at/netinfo/netinfo/hosts.txt
+.. [#fhosts] The :term:`hosts.txt` file is not maintained anymore. A historical snapshot dated April 19th, 1984 is available from https://www.saildart.org/HOSTS.TXT%5BHST,NET%5D15
 
 .. [#fdnstimeline] See http://www.donelan.com/dnstimeline.html for a time line of DNS related developments. 
 

diff --git a/book/links.rst b/book/links.rst
@@ -16,7 +16,7 @@
 
 .. _Unicode: http://en.wikipedia.org/wiki/Unicode
 
-.. _Internet drafts: http://www.ietf.org/id-info/
+.. _Internet drafts: https://www.ietf.org/standards/ids/
 
 .. _telnet: http://en.wikipedia.org/wiki/Telnet
 
@@ -36,7 +36,7 @@
 
 .. _Richard Stevens: http://www.kohala.com/
 
-.. _Van Jacobson: http://www.parc.com/about/people/88/van-jacobson.html
+.. _Van Jacobson: https://en.wikipedia.org/wiki/Van_Jacobson
 
 .. _Sally Floyd: http://www.icir.org/floyd/
 
@@ -156,7 +156,7 @@
 
 .. _cisco: http://www.cisco.com
 
-.. _level3: http://www.level3.com
+.. _level3: https://www.lumen.com
 
 .. _google: http://www.google.com
 

diff --git a/book/network/bgp.rst b/book/network/bgp.rst
@@ -617,7 +617,7 @@ Due to this organisation of the Internet and due to the BGP decision process, mo
 
 .. [#fgranularity] Some researchers such as [MUF+2007]_ have shown that modelling the Internet topology at the AS-level requires more than the `shared-cost` and `customer->provider` peering relationships. However, there is no publicly available model that goes beyond these classical peering relationships.
 
-.. [#fbgpdata] BGP data is often collected by establishing BGP sessions between Unix hosts running a BGP daemon and BGP routers in different ASes. The Unix hosts stores all BGP messages received and regular dumps of its BGP routing table. See http://www.routeviews.org, http://www.ripe.net/ris, http://bgp.potaroo.net or http://irl.cs.ucla.edu/topology/
+.. [#fbgpdata] BGP data is often collected by establishing BGP sessions between Unix hosts running a BGP daemon and BGP routers in different ASes. The Unix hosts store all BGP messages received and regular dumps of their BGP routing tables. See http://www.routeviews.org, https://www.ripe.net/ris, or https://bgp.potaroo.net
 
 
-.. [#fpotaroo] Several web sites collect and analyse data about the evolution of BGP in the global Internet. http://bgp.potaroo.net provides lots of statistics and analyses that are updated daily.
+.. [#fpotaroo] Several web sites collect and analyse data about the evolution of BGP in the global Internet. https://bgp.potaroo.net provides lots of statistics and analyses that are updated daily.
diff --git a/book/transport/tcp.rst b/book/transport/tcp.rst
@@ -398,7 +398,7 @@ Once the round-trip-time measurements have been collected for a given TCP connec
 
 The original TCP specification proposed in :rfc:`793` to include two additional variables in the TCB : 
 
- - `srtt` : the smoothed round-trip-time computed as :math:`srrt=(\alpha \times srtt)+( (1-\alpha) \times rtt)` where `rtt` is the round-trip-time measured according to the above procedure and :math:`\alpha` a smoothing factor (e.g. 0.8 or 0.9)
+ - `srtt` : the smoothed round-trip-time computed as :math:`srtt=(\alpha \times srtt)+( (1-\alpha) \times rtt)` where `rtt` is the round-trip-time measured according to the above procedure and :math:`\alpha` a smoothing factor (e.g. 0.8 or 0.9)
  - `rto` : the retransmission timeout is computed as :math:`rto=min(60,max(1,\beta \times srtt))` where :math:`\beta` is used to take into account the delay variance (value : 1.3 to 2.0). The `60` and `1` constants are used to ensure that the `rto` is not larger than one minute nor smaller than 1 second.
 
 However, in practice, this computation for the retransmission timeout did not work well. The main problem was that the computed `rto` did not correctly take into account the variations in the measured round-trip-time. `Van Jacobson` proposed in his seminal paper [Jacobson1988]_ an improved algorithm to compute the `rto` and implemented it in the BSD Unix distribution. This algorithm is now part of the TCP standard :rfc:`2988`.
@@ -789,7 +789,7 @@ In general, the maximum throughput that can be achieved by a TCP connection depe
 
 .. [#faveragebandwidth] A precise estimation of the maximum bandwidth that can be achieved by a TCP connection should take into account the overhead of the TCP and IP headers as well.
 
-.. [#ftcphosts] See http://fasterdata.es.net/tuning.html for more information on how to tune a TCP implementation
+.. [#ftcphosts] See https://fasterdata.es.net/host-tuning/ for more information on how to tune a TCP implementation
 
 .. [#frttmes] In theory, a TCP implementation could store the timestamp of each data segment transmitted and compute a new estimate for the round-trip-time upon reception of the corresponding acknowledgement. However, using such frequent measurements introduces a lot of noise in practice and many implementations still measure the round-trip-time once per round-trip-time by recording the transmission time of one segment at a time :rfc:`2988`