Carriers L1-L7
Carriers — 29 vendors and operators, each broken down by layer L1 to L7: what they sell at that layer, and which layer is their home turf.
AT&T
Home turf: L1
L1 Physical
This is the most important layer in the domain, because it contains two things no other domain can offer. First, the last mile: every earlier domain on this site hands the segment from your own building to a facility or a cloud on-ramp back to a carrier — Me…
L2 Data Link
This is one of the domain's principal service layers, with more substance than in any preceding domain. Four product lines matter.
L3 Network
This is the thickest layer in the domain, because a carrier's core retail products live at layer 3. Five things matter, two of which no other domain can offer.
L4 Transport
This layer is where a carrier differs most from the preceding domains, because it is the only domain on the site that genuinely sells transport quality as a product. Four things matter.
L5 Session
This is a session layer where a carrier genuinely has products, in clear contrast with the two interconnection domains — Megaport L5 and Equinix L5 both state explicitly that they have nothing to do with voice or SIP, whereas here voice is a principal produc…
L6 Presentation
This layer is explicitly empty — no product or service. This domain's access and transport products are transparent forwarding — no inspection, no encryption of content; its network security business has been divested into an independent company (see L4), an…
L7 Application
Under the reading established at L4 this layer is thin: this domain performs no application-layer traffic processing — no WAF, no API gateway, no CDN, no application delivery and no global load balancing. It has two pieces of content here.
Cross-layer Ops & Governance
This is the layer most worth reading carefully in a carrier domain, because it covers the part of reality the other kinds of domain here barely touch: procurement, delivery, credits and contracts. Six blocks, each with one judgement that matters most.
Verizon
Home turf: L1
L1 Physical
The most effective way to read this domain is against this site's AT&T domain, because the two share a highly similar structure with the differences landing exactly at the points that matter.
L2 Data Link
This layer's second section describes a structural advantage specific to the US, one that makes diversify-by-medium genuinely achievable here in a way many other markets cannot manage.
L3 Network
This layer's second section is a deliberate addition on this site: what the case looks like from the broadband network's side of that peering dispute.
L4 Transport
This layer's second section follows on from L3's it-is-simultaneously-a-destination-for-traffic identity, and it delivers a capacity-planning judgment that many people do not realize they have gotten wrong.
L5 Session
This layer's third section covers content specific to the US, one that gives enterprises building their own private cellular network a path in the US that does not require buying spectrum from a carrier.
L6 Presentation
This layer has two sections, and what they describe is really two sides of the same thing: what you can assert for yourself, and what you simply have to accept.
L7 Application
This layer has two sections, and both land on the thing specific to this domain: the information inconsistency created by asset handovers.
NTT
Home turf: L1
L1 Physical
This layer is what makes the domain distinctive: it holds all three classes of physical asset that the preceding three domains each represent separately.
L2 Data Link
This layer holds something no other domain can offer, so state it first: the in-facility cross connect, metro and inter-city data centre interconnection, and trans-oceanic capacity can all come from one group.
L3 Network
This layer introduces a concept new to the site: a Tier-1 backbone. The global IP network it operates is one of the largest Tier-1 backbones in the industry — and a Tier-1 is defined by settlement-free peering with every other Tier-1, which means it need not…
L4 Transport
Two things deserve stating first at this layer. The first is an explicit contrast with the AT&T domain: there, the security business has been divested into a separate company, so managed security is delivered through partnership, whereas here the security bu…
L5 Session
This layer holds two substantial pieces, one a product and one an operational reality specific to this domain. The product is voice and unified communications: the third appearance of a genuine voice product line on this site (GCX L5 from a wholesale perspec…
L6 Presentation
This layer is explicitly empty — no product or service. This domain's access and transport products are transparent forwarding — no inspection, no encryption of content; the group's in-house security capability is managed security and SOC-class services (see…
L7 Application
This layer is slightly thicker than in the AT&T domain for one reason: the group contains a large systems integration business, so it has a class of 'product' at the application layer that no other domain has — deliverables.
Cross-layer: Management & Operations
The cross-layer proposition here fits in one sentence: the operational difficulty comes not from technology but from organisation.
Vodafone
Home turf: L1
L1 Physical
This layer needs to start by explaining how its footprint was built, because that determines what 'Vodafone's network' actually means in terms of ownership from one country to the next.
L2 Data Link
This layer is the standard Ethernet leased-line business that its Vodafone Business brand offers to enterprise customers, with mechanics no different in substance from this page's other carrier domains: point-to-point Ethernet leased lines and multipoint L2…
L3 Network
Beyond standard IP transit and enterprise IP VPN, the most notable thing at this layer is its global IoT connectivity business — this is a product line where it stands out more than most of this page's carrier domains: multi-country SIM/eSIM connectivity man…
L4 Transport
This layer is relatively thin — the billing mechanics for standard enterprise networks (flat-rate per port, 95th percentile) are the same as several of this page's domains, and are not repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers through Vodafone Business, in a form similar to this page's other major carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is dra…
L6 Presentation
The situation at this layer is the same as most of this page's major carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality sitting on the customer side; connections over managed SD-WAN and the IoT pla…
L7 Application
Two things at this layer. The IoT device management platform: this is the core delivery interface for this business line — device activation, status monitoring, data-pool management and billing are all handled through this platform, a mechanic similar to thi…
Comcast
Home turf: L1 / L2
L1 Physical
Several domains on this site lean on one claim: that in most populated parts of the US there are genuinely two unrelated wireline access networks, which makes diversifying by medium actually feasible there (this site's Verizon domain L2 argues this in full f…
L2 Data Link
This layer has three sections, and the first two are direct corollaries of the architectural fact covered in L1's second section — so they do not need to re-explain the mechanism, only spell out the consequences.
L3 Network
This layer's first section carries the most weight of any in this domain on this site, because it fills in a third viewpoint on a public dispute.
L4 Transport
This layer has three sections, and the mechanism covered in the first is specific to this medium, while the angle in the second has not been covered by any other domain on this site.
L5 Session
This layer has three sections, and the first has to resolve a fact that looks like it contradicts L3 but actually does not. A managed overlay network is not the same as owning the network: it acquired a set of global managed-network and security-service capa…
L6 Presentation
This layer has only two sections, and that is an honest reflection of the fact: this domain's weight sits in the access network, presentation-layer content is not broad to begin with, and padding it out would only dilute the parts that are actually useful.
L7 Application
This layer has two sections, and the first has to point out something many people on this domain never use: the key data for deciding where a problem lies does not live in the portal — it lives on your own device's diagnostics page.
T-Mobile
Home turf: L1
L1 Physical
This domain has one structural quirk on this site that shapes how to read the whole thing: it is the only large US carrier domain here with no legacy wireline access plant.
L2 Data Link
This layer has three sections, and the first two describe two sides of the same thing — two capacity constraints on the fixed wireless product that are rarely explained clearly.
L3 Network
This layer's first section forms an interesting pairing with this site's Jio domain L3: both took the IPv6-first route, but for completely different reasons, which illustrates something more general.
L4 Transport
All three sections of this layer are things you run into when treating a mobile link as an enterprise link, and the two things covered in the first two sections are almost always missed at selection time.
L5 Session
This layer's first section is the one in this domain most worth reading, because it lays out a decision sequence that many designs get backwards.
L6 Presentation
This layer has only two sections, and that is an honest reflection of the fact: this domain's presentation-layer content is not broad to begin with, and padding it out would only dilute the parts that are actually useful.
L7 Application
This layer likewise has only two sections, and both point to the same conclusion: the most critical observability data in this domain does not live in the carrier portal, so you have to collect it yourself.
Jio
Home turf: L1
L1 Physical
This layer needs to clear up two easily confused things before getting to the assets themselves. First: it holds spectrum. This site used to phrase this as a count ('only two domains have spectrum'), and that number has drifted twice as new domains were adde…
L2 Data Link
One section of this layer is unique to this domain, and it is the part most worth reading first: the link-layer properties of the radio bearer.
L3 Network
The section of this layer most worth reading is unique to this site, and its motive is not policy but arithmetic: there simply are not enough IPv4 addresses to hand out to a few hundred million subscribers.
L4 Transport
All three sections of this layer are specific to mobile networks, and the mechanism described in the first runs exactly opposite to fixed-line behaviour, so it is worth reading first.
L5 Session
Three sections in this layer, and the problem discussed in the second is common in enterprises yet is almost never correctly attributed.
L6 Presentation
Only two sections in this layer, and the first has to establish the version of this site's recurring judgment as it applies to mobile networks — possibly the most easily misunderstood of all these versions.
L7 Application
Only two sections in this layer, and that thinness is honest: this is a consumer-scale operator, not a global enterprise service provider.
Orange
Home turf: L1
L1 Physical
This layer is the most worthwhile layer to read in this domain, because it holds two assets that almost no other domain on this site has.
L2 Data Link
This layer is the foundational product of its enterprise business, and L2 circuits spanning Europe, Africa and the Middle East are its most competitive offering — the three things this layer needs to cover each carry a different weight.
L3 Network
This layer has one section that's content found nowhere else on this site, and it's the part of this domain most worth reading: why traffic between neighbouring African countries trombones through Europe.
L4 Transport
All three sections in this layer revolve around one shared premise: this domain's network spans regions with wildly different conditions, so transport-layer behaviour differs enormously between segments.
L5 Session
This layer has three sections, and the first has an angle specific to this domain. Managed SD-WAN: carrier-managed SD-WAN usually isn't a single vendor's solution — it's several vendors' foundations offered side by side for the customer to choose from — this…
L6 Presentation
This layer has three sections, and the second carries the most weight in this domain. Encryption ownership and national crypto regulations: who does the encrypting determines who can see the plaintext, and in a cross-border scenario there's an additional lay…
L7 Application
This layer has three sections; the first deals with the single most misleading thing about this domain, and the third is its substantive advantage relative to other domains on this site.
Telefónica Global Solutions
Home turf: L3
L1 Physical
This layer needs to start by drawing the boundary between this domain and other entities within the Telefónica group, because the Telefónica group's structure is more fragmented than most carrier domains on this page: domestic Spanish fixed and mobile busine…
L2 Data Link
This layer is its standard Ethernet leased-line business for multinational enterprise customers, with mechanics no different in substance from this page's other carrier domains: point-to-point Ethernet leased lines and multipoint L2 services, used to connect…
L3 Network
This is this domain's star layer: international IP transit and international voice wholesale are its core, historical business, relying on the group's international network relationships between Europe and Latin America.
L4 Transport
This layer is explicitly empty — no product or service. Billing and session-keepalive mechanics at this layer are industry-standard, already covered in full in this site's Cogent domain L4; split pricing across Europe and each Latin American country in a mul…
L5 Session
At this layer it offers managed SD-WAN to multinational enterprise customers, in a form similar to this page's other major carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how…
L6 Presentation
The situation at this layer is the same as most of this page's major carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality sitting on the customer side; tunnel connections over managed SD-WAN typicall…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
Singtel
Home turf: L3
L1 Physical
This layer needs to start by separating 'the group' from 'the network this operating entity actually runs itself' — this distinction matters more here than in most domains on this page, because a large part of its regional footprint is a shareholding relatio…
L2 Data Link
This layer is its standard Ethernet leased-line business for domestic Singapore and international directions, with mechanics no different in substance from this page's other carrier domains: point-to-point Ethernet leased lines and multipoint L2 services.
L3 Network
This is this domain's star layer, and also the product it genuinely operates directly itself, rather than acquiring indirectly through a shareholding relationship: Singtel Internet eXchange (STIX, autonomous system AS7473) is its international IP transit and…
L4 Transport
This layer is relatively thin — the mechanics are the industry-standard billing and session keepalive, already fully covered across several of this page's domains, so it is not repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this page's other major carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
The situation at this layer is the same as most of this page's major carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality sitting on the customer side; tunnel connections over managed SD-WAN typicall…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
Telstra International
Home turf: L1
L1 Physical
This layer needs to start with something highly similar to this page's TIM domain, just via a different mechanism: Australia's fixed-line access network (copper and HFC) has been progressively migrated since 2011 into NBN Co — a government-owned, wholesale-o…
L2 Data Link
This layer is its standard Ethernet leased-line business for enterprise and wholesale customers, with mechanics no different in substance from this page's other carrier domains: point-to-point Ethernet leased lines and multipoint L2 services, built on top of…
L3 Network
The core of this layer is autonomous system AS1221 — another network on this page that has long ranked near the top of global interconnection-density statistics (specific rankings per current data from bgp.he.net, PeeringDB and similar public sources; mechan…
L4 Transport
This layer is relatively thin — the mechanics are the industry-standard billing and session keepalive, already fully covered across several of this page's domains, so it is not repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this page's other major carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
The situation at this layer is the same as most of this page's major carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality sitting on the customer side; tunnel connections over managed SD-WAN typicall…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
KDDI
Home turf: L1
L1 Physical
This layer needs to start with its lineage, because that's what explains why its assets today are more complex than an ordinary domestic mobile operator's: it was formed from a 2000 merger of three companies — DDI (domestic long-distance and mobile), KDD (Ko…
L2 Data Link
This layer is its standard enterprise Ethernet-line business for corporate customers, with mechanics no different in substance from this site's other carrier domains: point-to-point Ethernet lines and multipoint L2 services, with international segments able…
L3 Network
This layer is its standard IP transit and enterprise IP VPN business. The domestic segment rides Japan's mature domestic mobile and fixed-line user base, while the international segment rides the KDD-legacy international gateway facilities — this combination…
L4 Transport
This layer's content is relatively thin; the mechanics are the industry-standard billing and session keepalive already covered in full elsewhere on this site, so they aren't repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this site's other large carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
This layer's position is the same as most of this site's other large carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality resting on the customer side; tunnel connections on managed SD-WAN typically…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management, with mechanics consistent with this site's other carrier domains.
Telecom Italia
Home turf: L1
L1 Physical
This layer needs to clarify one thing that stopped being a single answer after 2024: 'what network does Telecom Italia own' now needs to be answered in three separate parts, not lumped together as 'its network.' Part one, domestic fixed access in Italy: the…
L2 Data Link
This layer is its conventional Ethernet private-line business for enterprise customers, with mechanics no different in substance from this page's other carrier domains, but the underlying access is likewise affected by the wholesale network structure covered…
L3 Network
The weight of this layer sits with its international wholesale subsidiary, Sparkle: an internationally branded wholesale carrier operating independently, which owns and participates in multiple international submarine cable systems, covering routes around th…
L4 Transport
This layer is thin — the mechanics are the industry-standard billing and session keepalive, already fully covered at several of this page's domains; not repeated in detail.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a shape similar to the European-carrier managed SD-WAN covered at this page's Orange and Telia domains, with the core questions still being the same three: whose technology is underneath, how…
L6 Presentation
Two things at this layer. Encryption responsibility: conventional IP transit and VPN are transparent forwarding, not encrypted, with confidentiality sitting on the customer side; the managed SD-WAN overlay typically has built-in encryption, mechanics consist…
L7 Application
This layer is the conventional portal and support structure: a customer portal for viewing circuit status and usage, a ticketing/fault-reporting channel, and contract and billing management.
Lumen
Home turf: L1
L1 Physical
This layer is this domain's core asset and the layer it is flagged for — understanding it starts with understanding that what it actually owns is routes.
L2 Data Link
What's sold at this layer is a transparent Layer 2 channel between two points, and its relationship to the L1 assets is direct: Layer 2 services ride on its own routes, so wherever the route reaches, the Layer 2 service can be sold. Three blocks.
L3 Network
This is the hardest layer in this domain besides L1, and its weight comes from the Level 3 lineage: that autonomous system has long ranked among the most densely interconnected in the world, so a great deal of internet traffic inevitably passes through it (c…
L4 Transport
The most valuable thing at this layer isn't the product list, it's an explanation: why you bought a big-bandwidth long-haul link and measured throughput falls well short of the rated number.
L5 Session
There's really only one core question at this layer: who is establishing and controlling these sessions — you, or the carrier. Three blocks.
L6 Presentation
This layer needs to separate three things that are easy to conflate, and the boundaries between them are exactly what's most valuable here.
L7 Application
This layer needs one thing said up front, because it sets how high your expectations should be for this domain: its application-layer capability is narrower than most people assume, because the content-delivery business has already been sold off.
Telia
Home turf: L1
L1 Physical
The primary reason this domain exists is to correct an easy mistake, so that comes first. In networking circles, Telia's best-known identity is as the operator of that global IP backbone — a long-standing top-ranked autonomous system that sold international…
L2 Data Link
Three sections at this layer, and the second is the most valuable because it's this page's recurring "two different suppliers" judgment in its sharpest form in a regulated incumbent market.
L3 Network
The throughline at this layer is a reversal of role, and it's the most effective way into understanding this domain's current position.
L4 Transport
The first section at this layer covers something not covered elsewhere on this page, and it's a clean example of "latency dictates architecture": synchronous replication has a hard latency threshold, and distance directly decides whether zero data loss is ac…
L5 Session
Three sections at this layer, and the second has a Nordic-specific piece that genuinely changes what's practically achievable for remote access here.
L6 Presentation
Two sections at this layer, and the second has a practical point directly tied to L1: keeping data in-region is both the compliant location and the cheap location.
L7 Application
Only two sections at this layer, and the thinness is accurate: it's a regional carrier, not a global enterprise-services company. This page's Tata domain L7 has the full remote-production, global managed-security and cross-border professional-services set; t…
HiNet
Home turf: L1
L1 Physical
This layer needs to start with something that isn't a hypothetical but an event that actually happened: in February 2023, submarine cables connecting the outlying Matsu Islands were cut (public reporting attributed it to vessel activity), knocking out Matsu'…
L2 Data Link
This layer is its standard enterprise Ethernet-line business for corporate customers, with mechanics no different in substance from this site's other carrier domains: point-to-point Ethernet lines and multipoint L2 services.
L3 Network
The core of this layer is autonomous system AS3462 — it has long been Taiwan's principal internet service provider, and its domestic peering density and user base hold a dominant position in the Taiwanese market (specific rankings per current measurements fr…
L4 Transport
This layer's content is relatively thin; the mechanics are the industry-standard billing and session keepalive already covered in full elsewhere on this site, so they aren't repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this site's other large carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
This layer's position is the same as most of this site's other large carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality resting on the customer side; tunnel connections on managed SD-WAN typically…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
True Corporation
Home turf: L1
L1 Physical
This layer needs to start with the major 2023 transaction, because it determines how this domain's network should be understood today: True completed a merger with Total Access Communication (DTAC), combining what had been Thailand's third- and second-larges…
L2 Data Link
This layer is its standard enterprise Ethernet-line business for corporate customers, with mechanics no different in substance from this site's other carrier domains: point-to-point Ethernet lines and multipoint L2 services.
L3 Network
This layer is its standard IP transit and enterprise IP VPN business. Its post-merger subscriber base is now the largest in Thailand, which in theory brings a stronger peering-negotiation position, but whether that advantage has already translated into bette…
L4 Transport
This layer's content is relatively thin; the mechanics are the industry-standard billing and session keepalive already covered in full elsewhere on this site, so they aren't repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this site's other large carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
This layer's position is the same as most of this site's other large carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality resting on the customer side; tunnel connections on managed SD-WAN typically…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
PLDT
Home turf: L1
L1 Physical
This layer needs to start with a geographic reality most of this site's other domains never have to face: the Philippines is an archipelago nation made up of thousands of islands, so "inter-island connectivity" here is not a metaphor but a real engineering p…
L2 Data Link
This layer is its standard enterprise Ethernet-line business for corporate customers, with mechanics no different in substance from this site's other carrier domains: point-to-point Ethernet lines and multipoint L2 services.
L3 Network
This layer is its standard IP transit and enterprise IP VPN business; as the Philippines' incumbent carrier, domestic peering density and path quality are typically its relative strength (domestic traffic doesn't need to detour through an international gatew…
L4 Transport
This layer is explicitly empty — no product or service. Billing and session-keepalive mechanics at this layer are industry-standard, already covered in full in this site's Cogent domain L4; this domain has no standalone product at this layer distinct from ot…
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this site's other large carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
This layer's position is the same as most of this site's other large carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality resting on the customer side; tunnel connections on managed SD-WAN typically…
L7 Application
This layer is the standard portal and support system: a customer portal for circuit status and usage, ticketing and fault-reporting channels, contract and billing management.
Globe Telecom
Home turf: L7
L1 Physical
It faces the same Philippine archipelago geographic constraints (inter-island connectivity depending on submarine cable, international capacity concentrated in a limited number of landing stations) as this site's PLDT domain; the full treatment is in the PLD…
L2 Data Link
This layer is its standard enterprise Ethernet-line business for corporate customers, with mechanics no different in substance from this site's other carrier domains: point-to-point Ethernet lines and multipoint L2 services.
L3 Network
This layer is its standard IP transit and enterprise IP VPN business, with mechanics consistent with this site's other incumbent carrier domains.
L4 Transport
This layer's content is relatively thin; the mechanics are the industry-standard billing and session keepalive already covered in full elsewhere on this site, so they aren't repeated here.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a form similar to this site's other large carrier domains, and the core questions remain the same three: whose technology sits underneath, how the demarcation is drawn, and how long changes t…
L6 Presentation
This layer's position is the same as most of this site's other large carrier domains: standard IP transit and Ethernet are transparent forwarding, unencrypted, with confidentiality resting on the customer side; tunnel connections on managed SD-WAN typically…
L7 Application
This is this domain's flagship layer, because outside its telecom business it has achieved something at a scale no other carrier domain on this site has matched: GCash is its mobile wallet/fintech platform (operated through its subsidiary Mynt, with outside…
Colt Technology Services
Home turf: L1 / L5
L1 Physical
This layer needs to start with this domain's historical origin, since it still shapes its positioning today: founded in London in 1992, with the name coming from 'City of London Telecommunications' — created specifically to give City of London financial inst…
L2 Data Link
This layer is an Ethernet leased-line business built on top of the Colt IQ Network's metro fibre — mechanically the industry-standard point-to-point Ethernet leased line (EVPL) and multi-point Ethernet virtual private LAN (E-LAN/VPLS), already covered in ful…
L3 Network
This layer is a standard IP transit service, with mechanics and billing (typically 95th-percentile) matching the industry-standard approach covered in this page's Cogent domain L3, not repeated here.
L4 Transport
This layer is a standard service-class and SLA mechanism — tiered queuing, DSCP marking, and latency/jitter/packet-loss SLA commitments, with mechanics matching the industry-standard approach discussed in this page's other carrier domains.
L5 Session
This is this domain's second star layer: managed SD-WAN aimed at enterprise customers, in a shape similar to this page's other large carrier domains, with the same three core questions still applying — whose underlying technology is it, how far does fault is…
L6 Presentation
This layer is explicitly empty — no product or service. This domain's access and transport products are transparent forwarding — no inspection, no encryption of content; whether to encrypt is the customer's own choice within its protocol stack, something thi…
L7 Application
This layer has two pieces. Voice and unified communications: enterprise SIP trunking and unified-communications services, a common product line for this kind of pan-European enterprise carrier domain.
Tata Communications
Home turf: L1
L1 Physical
This domain is best read against this site's Jio domain, because the two share a country while being near-opposites: Jio is a consumer-scale domestic operator with spectrum and hundreds of millions of subscribers; this domain does no consumer business at all…
L2 Data Link
Three sections in this layer, and the third covers something no other domain on this site does: broadcast and live media transport. Start with the first two.
L3 Network
Three sections in this layer, and the second contains a judgment worth calling out on its own, because it can make you believe you bought redundancy that in fact does not exist.
L4 Transport
The centre of gravity in this layer is something no other domain on this site has covered: the transport-layer requirements of international voice transport.
L5 Session
Three sections in this layer, the first containing a structure specific to this domain, and the third covering something no other place on this site does.
L6 Presentation
Two sections in this layer, and the first has to state a fact neutrally but plainly, because it is exactly the reason customer-side encryption genuinely matters.
L7 Application
Three sections in this layer, and the second covers something no other place on this site does, also the most distinctive application-layer business in this domain.
Zayo
Home turf: L1
L1 Physical
This layer is the star layer for this domain, and the only entry point for understanding it: what it sells is one layer below what other domains on this page sell — not lit Internet access, but unlit fibre itself and wavelength channels, which the customer t…
L2 Data Link
This layer is one step up from dark fibre and wavelengths: a customer who doesn't want to manage the optical layer itself can just buy a pre-lit Ethernet private line, with mechanics no different in substance from Ethernet services at this page's other carri…
L3 Network
This domain's position at this layer needs to be stated honestly: IP transit is not its core, recognizable product — L1 is. It does offer an IP transit service, but what's more worth recording is cloud connectivity: inside zColo facilities, customers can int…
L4 Transport
This layer covers the special commercial shape of its products, not the transport protocol itself. For physical-layer products like dark fibre and wavelengths, the common contract shape is an IRU (Indefeasible Right of Use — a one-time or installment payment…
L5 Session
This layer is explicitly empty — no product or service. This domain sells dark fibre, wavelengths and cabinet colocation — a physical-layer wholesale business whose customers are mainly other networks and large institutions, not an enterprise networking prov…
L6 Presentation
This layer is explicitly empty — no product or service. This domain has no encryption-class product: its Ethernet and IP transit products (see L2, L3) match this page's other carrier domains — transparent forwarding, no inspection, with encryption left to th…
L7 Application
This layer is the conventional portal and support structure, with mechanics no different in substance from this page's other carrier domains: a customer portal for viewing circuit status and usage, a ticketing/fault-reporting channel, and contract and billin…
PCCW Global
Home turf: L3
L1 Physical
This layer needs to first distinguish it from another entity readers of this page easily confuse it with: Hong Kong's domestic fixed-line, broadband and mobile business is operated by HKT (the independently listed HKT Trust / HKT Limited); this domain is the…
L2 Data Link
This layer is its conventional Ethernet private-line business for enterprise and wholesale customers, with mechanics no different in substance from this page's other carrier domains: point-to-point Ethernet private lines and multipoint Layer 2 service, built…
L3 Network
This is the star layer for this domain, with two things standing side by side. One, conventional IP transit: an Asia-Pacific backbone network operated over autonomous system AS3491, one of the region's major international carriers (for specific peering densi…
L4 Transport
This layer is thin — the mechanics are the industry-standard billing and session keepalive, already fully covered at several of this page's domains; not repeated in detail.
L5 Session
At this layer it offers managed SD-WAN to enterprise customers, in a shape similar to this page's other large carrier domains, with the core questions still being the same three: whose technology is underneath, how far does the fault boundary extend, and how…
L6 Presentation
This layer's situation is consistent with most of this page's pure-transit/enterprise-network domains: conventional IP transit and Ethernet are transparent forwarding, not encrypted, with confidentiality sitting on the customer side; tunnel connections on ma…
L7 Application
The weight of this layer still sits with Console Connect: its portal and API are not just lookup tools — they are themselves the product's core delivery interface: provisioning, changing and tearing down a connection all happen here, different from the model…
Cogent
Home turf: L3
L1 Physical
This layer is the entry point for understanding the whole domain, because its business model is itself an L1 strategy: it only sells into buildings it already covers, and it will generally not build new access to reach you.
L2 Data Link
This layer is its second product line, and the key to understanding it is the same as L1: the product is deliberately kept thin, with few options — and that is exactly what buys the low price.
L3 Network
This layer is this domain's core business, and the layer it stars — it is, at bottom, a company that sells IP transit, and everything else is a supporting act. Three sections.
L4 Transport
This layer covers three sections, each more practical than the last. Billing model: one real difference from most carriers is the flat-port shape — a fixed monthly fee by port speed, with no traffic metering — that is a genuinely concrete advantage for busin…
L5 Session
This layer needs one thing said up front, because it determines how you should read every layer above it in this domain: it does not offer managed services.
L6 Presentation
This layer has only two sections, because it genuinely is thin here — and that thinness is itself a direct consequence of its model, worth stating plainly rather than glossing over.
L7 Application
This layer likewise has only two sections, for the same reason as L6: it doesn't do managed security, content delivery, or professional services, so there isn't material for those sections here.
GTT Communications
Home turf: L3
L1 Physical
This layer is explicitly empty — no product or service. In 2023 it sold its entire physical network (pan-European fibre and transatlantic subsea capacity) to I Squared Capital, which now operates it independently under the EXA Infrastructure brand — today it…
L2 Data Link
This layer needs one thing established first, because it determines how every later layer in this domain should be read: it owns neither physical access nor backbone fibre.
L3 Network
This is the star layer for this domain across the whole site, because it is what holds up the claim that 'the assets were sold, the backbone remains.' It operates autonomous system AS3257, a Tier-1 class network that has long ranked among the highest in glob…
L4 Transport
Two things at this layer, both centered on 'how to make good use of purchased backbone capacity.' Billing and capacity accounting: its IP transit and private lines face the same choice between flat-rate-per-port and 95th-percentile billing models covered at…
L5 Session
This is the product line it genuinely wants customers to remember after the divestiture: managed SD-WAN. The logic is direct: when an enterprise's WAN is inherently forced into a hybrid shape of 'private line plus Internet plus tunnel' (mechanics at L3), the…
L6 Presentation
This layer needs one thing made clear: the underlying transport it resells and integrates does not itself provide confidentiality, and where encryption responsibility sits needs to be confirmed product by product.
L7 Application
Three things at this layer. Portal and observability: the unified portal can show circuit and site status stitched together across multiple underlying suppliers, but a 'unified view' can easily mask the truth about which segment is at fault — which specific…
Hurricane Electric
Home turf: L3
L1 Physical
This layer needs its physical footprint clarified first, because it takes a different shape from most of this page's carrier domains: its core is its own data centre campus, not a self-owned long-haul fibre network spanning a wide area.
L2 Data Link
Two things at this layer, both the physical/link-layer foundation for the peering density story at L3, rather than independent commercial product lines.
L3 Network
This is the star layer for this domain, because its entire industry reputation is concentrated here. Autonomous system AS6939 has long been one of the networks with the highest number of peering sessions globally (for the specific ranking, go by bgp.he.net,…
L4 Transport
The content at this layer follows the same mechanics as this page's other pure-transit carrier domains (Cogent in particular); not repeated in detail, this just notes this domain's position.
L5 Session
This layer is explicitly empty — no product or service. This domain is a pure network-and-facility operator — IP transit, peering, cabinet colocation — with no managed SD-WAN, no remote-access gateway, nothing at the session layer.
L6 Presentation
It has no encryption-class product at this layer — as a pure IP transit and peering network, it is, like this page's Cogent domain, a transparent forwarder that neither inspects nor encrypts customer packets, and confidentiality sits entirely with the custom…
L7 Application
Products at this layer fall into two classes, and the first is more famous than at most carrier domains. Public community tools: bgp.he.net is a widely used public BGP / IP WHOIS lookup and visualization tool; network engineers use it to check an autonomous…
GCX
Home turf: L1 / L3
L1 Physical
This is the thickest layer in the GCX domain — the inverse of the cloud domains — because GCX genuinely owns physical infrastructure.
L2 Data Link
This layer is GCX's main enterprise delivery form: Ethernet private line services. The essential contrast with the cloud domains is worth stating: cloud L2 is about layer-2 capability disappearing, while carrier L2 is about delivering layer-2 capability acro…
L3 Network
This is the carrier's core service layer, with content unlike either the equipment or cloud domains. The first thing to master is the billing model: IP transit bills on the 95th percentile rather than total volume — sampled every five minutes, with the top 5…
L4 Transport
Carriers have few products at this layer, but one piece of knowledge is extremely valuable in practice: the bandwidth-delay product.
L5 Session
This layer is noticeably thin in the carrier domain and that should be stated plainly: GCX has no identity platform, no network access control, no in-house zero trust product of any depth and no privileged access management — those capability areas sit entir…
L6 Presentation
There is little content at this layer but one key insight deserves elaboration: carrier-provided encryption protects against third-party tapping, not against the carrier itself.
L7 Application
This is the thinnest layer in the whole reference, and stating that plainly is more useful than padding it out: GCX has essentially no in-house application-layer products — no WAF, no CDN, no email security, no API gateway, no content moderation and no appli…
Cross-layer: Management & Operations
The proposition at this layer differs fundamentally from the preceding eight domains. Equipment domains discuss operating devices you control and cloud domains discuss managing resources through a self-service console, whereas the carrier domain's core propo…
Megaport
Home turf: L2
L1 Physical
There is little content at this layer but the boundary is exceptionally clear: in the Megaport model you buy exactly one physical thing — a Port, a physical port in a data centre where Megaport is enabled — and everything after that is a software-defined vir…
L2 Data Link
This is Megaport's signature layer and where the entire commercial model lives: the VXC (virtual cross connect) — a point-to-point layer-2 connection provisioned on demand over an existing Port, taking effect in minutes, with bandwidth adjustable online, bil…
L3 Network
This is where the domain differentiates itself: MCR (Megaport Cloud Router) — a virtual routing instance deployed inside a PoP that runs BGP in the fabric with no hardware to buy and no cage or floor space to rent.
L4 Transport
This layer is the turning point of the domain, and the way to read it changes: from L4 upward Megaport builds almost nothing itself.
L5 Session
Read through the lens established at L4 and this layer follows naturally: Megaport takes no part in any application session, and the fabric is transparent to everything above it.
L6 Presentation
This layer is explicitly empty — no product or service. This domain sells layer-2/3 connectivity (Port, VXC, MCR/MVE) — it forwards your traffic without inspecting or encrypting the content; whether to encrypt is the customer's own choice within its protocol…
L7 Application
Under the reading established at L4 this is the thinnest layer in the domain: Megaport performs no application-layer traffic processing at all — no WAF, no API gateway, no DNS service, no CDN, no application delivery and no global load balancing.
Cross-layer: Management & Operations
The cross-layer proposition here differs from every preceding domain and fits in three sentences. First, the risk comes from being fast, not slow: the equipment domains guard against configuration drift and the carrier domain against process latency (see the…
Zenlayer
Home turf: L1 / L4
L1 Physical
The biggest difference between this layer and the two edge domains on this site is that its physical layer is something you can order directly.
L2 Data Link
This layer is thinner than its L1 but thicker than the L2 of the two edge domains here — because it does sell layer 2 connections and they do not. Three blocks.
L3 Network
This is the layer where it has real technical substance, and the thing most worth remembering is that it has its own AS number and BGP, but it is not a backbone owner.
L4 Transport
The protagonist of this layer is its layer 4 acceleration product, and the commonest reason that product gets bought by mistake is being taken for a CDN.
L5 Session
This layer is thin in most infrastructure domains, but here it holds something real: out-of-band management — and it exists precisely because what you rent is a physical server.
L6 Presentation
This layer is explicitly empty — no product or service. Its layer-4 acceleration product (see L4) doesn't terminate TLS — it only optimises the transport path in the middle; encryption and decryption still happen between your own server and client, something…
L7 Application
This layer is explicitly empty — no product or service. What it gives you is a place to run applications (bare-metal servers and cloud networking, covered at the earlier layers), not the capability to process applications — it has no WAF, no CDN-level conten…
Cross-layer Ops & Governance
This is the layer most worth reading carefully in this domain, not because its operational features are many but because its operational shape differs structurally from the large-vendor domains here: your assets are scattered across markets where you have no…