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I can't understand the meaning of this paragraph!

But in our brief description of TCP and UDP, conspicuously missing was any mention of throughput or timing guarantees— services not provided by today’s Internet transport protocols.

is "conspicuously missing" the subject of the sentence? or "conspicuously" is the subject?
What does that dash mean before "services"?
It doesn't make sense to me not at all!

In other words I can't understand meaning of

conspicuously missing was any mention of throughput or timing guarantees—

part!

There are two verbs in that sentence that have a subject. These are was and provided.

Was is a little confusing because it's in a non-standard order. To be is a linking verb, so it can take an adjective as object - and in certain circumstances it can be OVS rather than SVO, which is what has happened here. The object is conspicuously missing, that is the adjective missing modified by the adverb conspicuously. The subject is any mention of throughput or timing guarantees, a noun phrase.

Provided is in passive voice, so the subject is services and there's no object, but the adverbial provides what would have been the subject if it were in active voice - today's Internet transport protocols. If it were in active voice, it would be "today's Internet transport protocols do not provide these services".

But in our brief description of TCP and UDP, conspicuously missing was
any mention of throughput or timing guarantees— services not provided
by today’s Internet transport protocols.

The subject is “any mention of throughput or timing guarantees”.

The dash signals what appears to be a supplementary appositive NP, one that can substitute for the matrix NP.

"Conspicuously missing" is a preposed adjective phrase in which "conspicuously" modifies "missing". It functions as predicative complement of "be" in its ascriptive sense.

The basic non-preposed equivalent makes things clearer:

But in our brief description of TCP and UDP, any mention of throughput or timing guarantees – services not provided by today’s Internet transport protocols -- was conspicuously missing.

The subject of the sentence is "any mention of throughput or timing guarantees." It's a case where, when people try to sound smarter OR want to prequalify something, they place the syntax in a non-standard order.

The sentence essentially reads:

Mention of throughput and timing guarantees, which are services not provided by todays Internet transport protocols, were conspicuously missing in our brief description of TCP and UDP

For the second part, we have "conspicuously," meaning "obviously" or "clearly;" "throughput," or "amount passing through a system or process" or "what passes through the process;" and "timing guarantees," which research shows is the "amount of time a website is active."

The phrase as a whole says that

"Information on the amount of data passing through the system and the amount of uptime of a website are obviously missing"

The dash in front of "guarantees" indicates that this was a pause, and that the following phrase was describing the prior two.

As such, the whole sentence reads:

"Information on the amount of data passing through the system and the amount of uptime of a website, which are services not provided by today's Internet transport protocols, are obviously missing in our short description of TCP and UDP"

Or, more succinctly:

"Information on data transportation and website uptime is obviously not in our description of TCP and UDP, and these services are not provided by Internet Transport protocols"