To understand who might be affected, we need to look at how Pakistan’s international connectivity is structured.
Key Submarine Cable Systems in Pakistan
- PTCL is the landing party for several major submarine cable systems: SEA-ME-WE-3, SEA-ME-WE-4, I-ME-WE, and AAE-1.
- There are a total of six submarine cables linking Pakistan internationally: SMW3, SMW4, SMW5, IMEWE, AAE-1, and TW1.
- Transworld Associates (TWA) is the operator/landing party for the TW1 cable, which is privately owned and connects Pakistan to UAE/Oman.
- Cybernet (Cyber Internet Services) is the landing party for the PEACE cable, which is a relatively new addition to Pakistan’s submarine cable network.
- PTCL is also joining the Africa-1 cable consortium; that cable has been landed in Karachi recently, expected to go operational soon.
So, multiple cables bring international bandwidth into Pakistan, but PTCL controls several of the major ones (SMW4, IMEWE, AAE-1) that carry a large share of traffic.
Shared vs Exclusive Infrastructure
- Many ISPs do not have their own international submarine cable access — they lease bandwidth or use PTCL’s infrastructure.
- PTCL, due to its role, is deeply woven into the backbone of connectivity for other ISPs.
- Transworld’s TW1 gives it some independence for international routing, especially when PTCL-controlled cables are under stress.
Because of this structure, disruptions in PTCL-managed cables (or in shared parts of the network) can ripple beyond just PTCL customers.
Past Incidents Show It’s Not Just PTCL
Historical events support the idea that cable faults affect all ISPs, not just PTCL’s customers:
- In September 2025, PTCL reported cuts near Jeddah affecting SMW4 and IMEWE segments, which resulted in broad service degradation across Pakistan during peak hours.
- The IT Minister confirmed that a submarine cable cut near Jeddah was indeed causing nationwide internet disruptions, not isolated ones.
- In a 2024 incident, faults in the AAE-1 cable impacted connectivity for many users in Pakistan.
- Analysts have noted that because most international traffic must traverse undersea cables, damaging one can have outsized consequences.
These events show that when a major submarine cable (especially one heavily used by PTCL) is affected, the impact typically isn’t confined to just one ISP’s user base.
Which ISPs Might Be Less Affected?
Some ISPs have structural advantages that may buffer them against total collapse of service:
- Transworld / TWA (TW1 cable)
- As the owner/operator of its own cable (TW1), Transworld has a separate path for international connectivity.
- Thus, during disruptions on PTCL-controlled cables, Transworld’s network (and its end-users) may see less severe degradation (or may employ fallback to TW1).
- However, if a cable fault occurs in a shared transit zone or upstream of TW1’s interconnects, the advantage may diminish.
- Cybernet / PEACE Cable
- Cybernet’s control of the PEACE cable gives it an additional independent source of international bandwidth.
- This can help Cybernet’s customers suffer less impact during outages affecting PTCL’s cables, depending on how routing is arranged.
- ISPs with Peering / Alternate Paths
- ISPs that maintain peering arrangements, backup routes, or use multiple upstream providers may better absorb disruptions.
- But in Pakistan, cross-border terrestrial backup paths (for example, via India or Afghanistan) are limited for political or infrastructure reasons, reducing redundancy.
However, these “less affected” ISPs might still feel performance drops or delays if the fault is massive or affects upstream aggregation points — it isn’t a guarantee of immunity.
Why a Cable Fault Affects Everyone (or Many)
Here are the technical reasons why a scheduled maintenance or fault on a submarine cable often leads to widespread slowdown across multiple ISPs:
- Shared bandwidth backbone: Many ISPs depend on the same undersea cable systems or upstream transit providers. If that route is impaired, traffic must be rerouted through the remaining cables, causing congestion.
- Limited redundancy: Even though Pakistan has multiple cables, the redundancy is fragile and capacity may not suffice to carry all shifted traffic without performance loss.
- Traffic rerouting delays & latency: When one path goes down, routing protocols take time to re-adjust. The new routes may incur higher latency or longer paths.
- Bottlenecks in the core: Even if an ISP has its own cable or link, the point where traffic aggregates (e.g. exchange points, interconnects) may still use the shared network path segments.
- Scale of the disruption: If a large section of a cable is under repair, some segments may be unusable entirely, forcing traffic to use much longer alternate links.
Likely Scenario for the Current Maintenance
- If the scheduled maintenance impacts one of PTCL’s major undersea cables (e.g. SMW4, IMEWE, AAE-1), which carry a heavy portion of international bandwidth, many ISPs will feel the impact to varying degrees.
- Users on ISPs with independent backhaul may fare slightly better, but might still face lag in peak hours or for international traffic.
- PTCL customers are likely to see more pronounced effects, because the maintenance is directly on PTCL’s infrastructure.
- The exact impact will depend on how well rerouting, load balancing, and backup bandwidth are managed during the maintenance window.
