EPISTEME · Glossary

The locked vocabulary

A corpus that claims rigour cannot call the same thing by two names. These terms do not vary between entries or between languages: they are the reference for whoever writes, whoever translates and whoever reads.

active optical cable

Known as AOC. Optics built into both ends, reach of tens of metres, flexible cabling. The natural step once copper no longer reaches.

In all three languages PT cabo óptico ativo · ES cable óptico activo

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

adaptive routing

Real-time traffic diversion when a path congests, without waiting for the application layer to notice.

In all three languages PT roteamento adaptativo · ES enrutamiento adaptativo

Where it appears InfiniBand: from SDR to XDR

cage

The physical receptacle where the module is inserted. At NDR one OSFP cage commonly serves two 400 Gb/s ports: counting cages as ports undersizes the switch by half. How many ports a cage has is a question of configuration before it is a physical fact.

In all three languages PT cage · ES cage

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

collective operation

An exchange in which all nodes combine partial results and nobody moves on until the last one finishes. It is the communication pattern of distributed training.

In all three languages PT operação coletiva · ES operación colectiva

Where it appears InfiniBand: from SDR to XDR

credit-based flow control

The mechanism that makes the fabric lossless: the sender only transmits once the receiver has guaranteed room to receive.

In all three languages PT controle de fluxo por crédito · ES control de flujo por crédito

Where it appears InfiniBand: from SDR to XDR

effective rate

What remains of the nominal rate after encoding overhead. QDR advertised as 40 Gb/s delivers 32. Comparing generations by nominal rate is comparing different quantities.

In all three languages PT taxa útil · ES tasa útil

Where it appears InfiniBand: from SDR to XDR

encoding

The scheme that inserts synchronisation bits into the stream. 8b/10b consumes 20% of the link; 64b/66b, roughly 3%. Not a detail: it is the difference between the datasheet number and what arrives.

In all three languages PT codificação · ES codificación

Where it appears InfiniBand: from SDR to XDR

entry

The unit of the corpus: a versioned text with auditable sources, an update date and a next-review date. It is not a blog post, which is why it does not age in silence.

In all three languages PT verbete · ES entrada

fabric

The set of switches, cables and adapters treated as one system rather than a sum of parts. The network is a chain in series: the result is that of the weakest link.

In all three languages PT fabric · ES fabric

Where it appears InfiniBand: from SDR to XDR

fat-tree

Topology in which bandwidth does not narrow as you climb: each layer aggregates enough not to create a bottleneck. It is the default AI cluster design with no oversubscription.

In all three languages PT fat-tree · ES fat-tree

Where it appears The connector fits. That means nothing.

ferrule

The ceramic face of an optical connector, where the fibres end in alignment. An MPO-12 has twelve positions on the ferrule and a four-lane variant lights eight.

In all three languages PT ferrule · ES ferrule

Where it appears The connector fits. That means nothing.

InfiniBand

Interconnect architecture in which the network adapter reads and writes directly into the remote server's memory, bypassing the operating system. Not 'a faster network': a network with a different path.

In all three languages PT InfiniBand · ES InfiniBand

Where it appears InfiniBand: from SDR to XDR

justified knowledge

ἐπιστήμη · episteme. A claim that survives the demand for justification: it has a cited, verifiable source. It is the declared regime of the technical entries in this corpus.

In all three languages PT conhecimento justificado · ES conocimiento justificado

lane

Each individual serial path in a link. The most common cluster width is x4, four lanes grouped into one port. The number on the datasheet is the sum of the lanes, never one of them.

In all three languages PT lane · ES lane

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

latency

The time between sending and receiving. In a collective operation it is what decides the outcome, because the whole group moves at the pace of the last one.

In all three languages PT latência · ES latencia

Where it appears InfiniBand: from SDR to XDR

leaf

The access switch, at the top of the rack, where the nodes connect. It is one half of the spine-and-leaf pair.

In all three languages PT leaf · ES leaf

Where it appears The connector fits. That means nothing.

leg

Each branched end of a splitter cable, the one that goes in the host. It is always RHS, flat-top. Reversing leg and trunk is not an error anyone fixes in the field.

In all three languages PT leg · ES leg

Where it appears The connector fits. That means nothing.

link width

How many lanes make up a port. Written as x1, x4 or x12. It is what turns the per-lane rate into the port rate.

In all three languages PT largura de link · ES ancho de enlace

Where it appears InfiniBand: from SDR to XDR

lossless fabric

A fabric where the packet is not dropped under congestion, because it is never sent without guaranteed room at the destination. In a collective operation, one retransmission delays the entire group.

In all three languages PT rede sem perda · ES red sin pérdida

Where it appears InfiniBand: from SDR to XDR

oversubscription

Selling more bandwidth at the edge than exists in the core. Acceptable in an enterprise network, expensive in a collective operation: the whole group moves at the pace of the last one.

In all three languages PT oversubscription · ES oversubscription

Where it appears The connector fits. That means nothing.

passive copper

Copper cable with no electronics, known as DAC. Lowest latency, lowest cost, near-zero power draw, and a reach of a few metres that shortens with every generation.

In all three languages PT cobre passivo · ES cobre pasivo

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

reach

The distance a medium covers without losing signal integrity. It shortens with every generation because closer signal levels reduce noise tolerance.

In all three languages PT alcance · ES alcance

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

reasoned opinion

δόξα · doxa. Direct observation, inference and professional judgment. It is not justified knowledge, which is why it is declared: the author saw one part, in one context, and may be wrong.

In all three languages PT opinião fundamentada · ES opinión fundamentada

spine

The aggregation layer that interconnects the leaf switches. Distinct from backbone, which is the long-haul stretch between rooms or buildings.

In all three languages PT spine · ES spine

splitter

A cable that opens one wide port into two or more narrow ones. It has a trunk and several legs, and the ends are not interchangeable.

In all three languages PT splitter · ES splitter

Where it appears The connector fits. That means nothing.

transceiver

Removable module that converts electrical signal into optical and back. Used with fibre for reaches of hundreds of metres to kilometres. Priced per pair, not per cable.

In all three languages PT transceptor · ES transceptor

Where it appears InfiniBand: from SDR to XDR · The connector fits. That means nothing.

trunk

The single end of a splitter cable, the one that goes in the switch. It is always IHS, finned-top, and does not fit an adapter cage.

In all three languages PT trunk · ES trunk

Where it appears The connector fits. That means nothing.

uplink

The link that climbs from the leaf to the aggregation layer. In a fat-tree with no oversubscription there is one uplink per compute link, and it is almost always optical.

In all three languages PT uplink · ES uplink

Where it appears The connector fits. That means nothing.