aboutsummaryrefslogtreecommitdiff
path: root/content/docs
diff options
context:
space:
mode:
Diffstat (limited to 'content/docs')
-rw-r--r--content/docs/network_protocols.md135
1 files changed, 135 insertions, 0 deletions
diff --git a/content/docs/network_protocols.md b/content/docs/network_protocols.md
new file mode 100644
index 0000000..d162945
--- /dev/null
+++ b/content/docs/network_protocols.md
@@ -0,0 +1,135 @@
+---
+title: "Packet network protocols"
+author: "Dimitri Staessens"
+description: "what"
+date: 2019-09-05
+#type: page
+draft: false
+---
+
+Packet switched networks move data between two applications using
+_protocols_, which specify where to move the data and how to do it.
+The Internet famously uses the Internet Protocol, IP (versions 4 and
+6, which are mutually incompatible, so in essence, there is not a
+single Internet, there are two!) as the network protocol that
+specifies how to move packets from point _A_ to point _B_. On top, it
+has the Transport Control Protocol (TCP) that takes care of things
+when IP packets get lost. TCP also does some other neat things, like
+making sure that a client does not send faster than a server can
+process, usually called _flow control_; and making sure that the
+network doesn't get overwhelmed by its users, usually called
+_congestion control_.
+
+The IPv4 protocol is specified in
+[RFC791](https://tools.ietf.org/html/rfc791), and its _header_ is
+shown here:
+
+```
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |Version| IHL |Type of Service| Total Length |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Identification |Flags| Fragment Offset |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Time to Live | Protocol | Header Checksum |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Source Address |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Destination Address |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Options | Padding |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+```
+
+The IPv6 protocol is specified in
+[RFC2460](https://tools.ietf.org/html/rfc2460), and its header format
+is:
+
+```
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |Version| Traffic Class | Flow Label |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Payload Length | Next Header | Hop Limit |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ + +
+ | |
+ + Source Address +
+ | |
+ + +
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ + +
+ | |
+ + Destination Address +
+ | |
+ + +
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+```
+
+For a detailed description of what all the fields in this protocol
+mean, we gladly refer you to the RFCs or the wikipedia pages (
+[IPv4](https://en.wikipedia.org/wiki/IPv4) and
+[IPv6](https://en.wikipedia.org/wiki/IPv6)). The most interesting
+fact about the jump from IPv4 to IPv6 is that the protocol got
+noticeably simpler.
+
+As Ouroboros tries to preserve privacy as much as possible, it has an
+*absolutely minimal network protocol* (it's also configurable, this is
+the 64 bit address, 16 bit EID version):
+
+```
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |
+ + Destination Address +
+ | |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Time-to-Live | QoS | ECN | EID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | EID |
+ +-+-+-+-+-+-+-+-+
+```
+
+The fields are:
+
+* Destination address: This specifies the address to forward the
+ packet to. The width of this field is configurable based on various
+ preferences and the size of the envisioned network. The Ouroboros
+ default is 64 bits. Note that there is _no source address_, this is
+ agreed upon during _flow allocation_.
+
+* Time-to-Live: Similar to IPv4 and IPv6 (where this field is called
+ Hop Limit), this ensures that packets don't get forwarded forever in
+ the network, for instance due to (transient) loops in the forwarding
+ path.
+
+* QoS: Ouroboros supports Quality of Service via a number of methods
+ (out of scope for this page), and this field is used to prioritize
+ scheduling of the packets when forwarding. For instance, if the
+ network gets congested and queues start filling up, higher priority
+ packets (e.g. a voice call) get scheduled more often than lower
+ priority packets (e.g. a file download).
+
+* ECN: This field specifies Explicit Congestion Notification (ECN),
+ with similar intent as the ECN bits in the DSCP field in IPv4 / ToS
+ field in IPv6. It has 8-bit width as a default, and gets set higher
+ as packets are deeper and deeper in a forwarding queue. Ouroboros
+ enforces Forward ECN (FECN).
+
+* EID: The Endpoint Identifier (EID) field specified the endpoint for
+ which to deliver the packet. The width of this field is
+ configurable, the values of this field is chosen by the endpoints at
+ _flow allocation_. It can be thought of as an ephemeral port.
+
+---
+Changelog:
+
+2019 09 05: Initial version. \ No newline at end of file