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Diffstat (limited to 'content/en/blog/20220212-tcp-ip-architecture.md')
| -rw-r--r-- | content/en/blog/20220212-tcp-ip-architecture.md | 48 |
1 files changed, 24 insertions, 24 deletions
diff --git a/content/en/blog/20220212-tcp-ip-architecture.md b/content/en/blog/20220212-tcp-ip-architecture.md index 540d190..ca4f58a 100644 --- a/content/en/blog/20220212-tcp-ip-architecture.md +++ b/content/en/blog/20220212-tcp-ip-architecture.md @@ -78,14 +78,13 @@ application less nimble because some choices get anchored in the solution, for instance the choice for a certain encryption library or a certain database solution and directly calling these proprietary APIs from all parts of the application. This tightly locked in -dependency can cause serious problems if these dependencies seize to +dependency can cause serious problems if these dependencies cease to be available (deprecation) or show serious defects. Good design lets development velocities add up. Bad design choices -slow development because development progress that should be -independent starts to interlock. Ever tried running with your -shoelaces knotted to someone else? Whenever one makes a step forward, -the other has to catch up. +slow development because progress that should be independent starts to +interlock. Ever tried running with your shoelaces knotted to someone +else's? Whenever one makes a step forward, the other has to catch up. Often, violations against these 2 principles are made in the name of optimization. Let's have a quick look at the trade-offs. @@ -162,14 +161,15 @@ efficiently!) taken care of at Layer 1 by a feature called Carrier Extension. Layer 2: The Ethernet II frame has an -[Ethertype](https://en.wikipedia.org/wiki/EtherType#Values) -itself is also a layer violation, specifying the encapsulated -protocol. 0x800 for IPv4, 0x86DD for IPv6, 0x8100 for tagged VLANs, etc. +[Ethertype](https://en.wikipedia.org/wiki/EtherType#Values), +which is also a layer violation, specifying the encapsulated +higher-layer protocol. 0x800 for IPv4, 0x86DD for IPv6, 0x8100 for +tagged VLANs, etc. Layer 3: Similarly as the Ethertype, IP has a [protocol](https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers) field, specifying the carried protocol. UDP = 17, TCP = 6. Other tight -couplings between layer 2 and layer 3 are, IGMP snooping and even +couplings between Layer 2 and Layer 3 are, IGMP snooping and even basic routing[^2]. One thing worth noting, and often disregarded in course materials on computer networks, is that OSI's 7 layers each had a _service definition_ that abstracts the function of each layer away @@ -282,16 +282,16 @@ If a protocol is designed with a flexible structure, but that flexibility is never used in practice, some implementation is going to assume it is constant. -Instead of the IP "Protocol" field in routers that I used abovee, the -usual example are _middleboxes_ -- hardware that perform all kinds of -shenanigans on unsuspecting TCP/IP packets. The reason why these boxes -_can_ work is because of the violations of the two important design -principles. The example from the wikipedia page, on how version -negotiation in TLS1.3 was +Instead of the IP "Protocol" field in routers that I used in the +example above, the usual examples are _middleboxes_ -- hardware that +perform all kinds of shenanigans on unsuspecting TCP/IP packets. The +reason why these boxes _can_ work is because of the violations of the +two important design principles. The example from the wikipedia page, +on how version negotiation in TLS1.3 was [preventing it from getting deployed](https://blog.cloudflare.com/why-tls-1-3-isnt-in-browsers-yet/), is telling. -But it happens deeper in the network stack as well. When we were +But it happens deeper down the network stack as well. When we were working on [the IRATI prototype](https://irati.eu/), we wanted to run RINA over Ethernet. The obvious thing to do is to use @@ -368,26 +368,26 @@ overwhelming consensus is that _"It's good enough"_ that is exactly what it will not be. A house built on an unstable foundation can't be fixed by replacing the furniture. Plastering the walls might make it look more appealing, and fancy furniture might even make it feel -temporarily like a "home" again. But however shiny the new furniture, -however comfortable the new queen-sized bed, at some time the once -barely noticeable rot seeping through the walls will become ever more -apparent, ever more annoying, and ever more impossible to ignore, so -that the only option left is to move out. +temporarily like "home" again. But however shiny the new furniture, +however comfortable the new queen-sized bed, at some point in time the +once barely-noticeable rot seeping through the walls becomes ever +more apparent, ever more annoying, ever harder to ignore, +until the only remaining option is to move out. When that realization comes, know that some of us have already started building on a different foundation. -As always, stay curious, +As always, stay curious. Dimitri -[^1]: I use Internet in a restrictive sense to mean the +[^1]: I use Internet in a restrictive sense, meaning the packet-switched TCP/IP network on top of the (optical) support backbones, not for the wider ecosystem on top of (and including) the _world-wide-web_. [^2]: How do IPv4 packets reach the default IP gateway? A direct - lookup by L3 into the L2 arp table! And why would IPv6 even + lookup by L3 into the L2 ARP table! And why would IPv6 even consider including the MAC address in the IP address if these layers were independent? |