Nokia 7750 SR-a8 — the operator service router

The 7750 SR family is Nokia's flagship multiservice provider-edge router. Where the 7705 SAR is the access/aggregation tier, the 7750 SR is the PE: where MPLS labels are imposed, where BGP carries route tables of a million prefixes, where every VPRN, VPLS, and EPipe ultimately terminates. The SR-a8 is the "augmented" compact variant — 8 service slots in a 4-RU chassis, designed for medium-density operator PoPs.

Family map (so the SR-a8 makes sense in context)

| Platform | Slots | Capacity | Use | |---|---|---|---| | 7750 SR-1, SR-1s | 1 fixed | up to ~36 Tbps (SR-1s) | Small PoP, edge | | 7750 SR-a4 / SR-a8 | 4 / 8 | multi-Tbps | Medium-density PE | | 7750 SR-7s | 7 service slots + 2 SFM | multi-Tbps | Larger PoP | | 7750 SR-14s | 14 + 4 SFM | dozens of Tbps | Large core/edge | | 7950 XRS | 16-40 slot | exabit-class | Hyperscale core |

All run the same SR OS (the same one as the 7705 SAR).

SR-a8 hardware

• 4 RU, 19" rack.
• 8 service slots (MDAs / IOMs depending on terminology).
• Dual CPM (Control Processor Module) for redundancy.
• Power: redundant AC or DC.
• Cooling: front-to-back.
• Module choice drives everything: 10G, 25G, 40G, 100G, 400G, plus specialty cards for OTN, MACsec, services.

What it's for

The 7750 SR-a8 sits as a Provider Edge (PE) in an operator's MPLS network. Three primary jobs:

1. Terminate customer access. SAPs face customers — EPipes for L2 point-to-point, VPRNs for managed L3 VPNs, IES for native internet.
2. Speak the operator-grade routing. OSPF / IS-IS to build the IGP underlay; iBGP (often with route reflectors) for VPN routes; eBGP for upstream / peer ASNs.
3. Carry MPLS labels. Either via LDP (IGP-aligned LSPs) or via RSVP-TE / Segment Routing for engineered paths and fast reroute.

A realistic PE setup snippet

[object Object],[object Object],[object Object],[object Object],[object Object]

That's a full L3VPN PE in maybe forty lines. The SR OS service model is famously clean once you've internalized the service / sdp / sap / vrf-target vocabulary.

What sets the 7750 apart operationally

• Hierarchical QoS that's actually usable: per-SAP egress queues with multi-tier scheduling, per-customer ingress policing, all defined as reusable templates.
• Hot software upgrade (ISSU). Push a new SR OS image to the standby CPM, switch over, push to the (now) standby. Done online, no traffic loss with good design.
• Hardware sec MACsec and IPsec for line-rate encryption where required.
• Segment Routing native support. Many modern operators are migrating from LDP/RSVP-TE to SR-MPLS on these platforms.

Day-to-day show commands

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What to remember

• 7750 SR is the PE in an MPLS operator network; SR-a8 = compact 8-slot variant.
• Same SR OS as the 7705 SAR — the CLI scales together with you.
• Speaks IGP (OSPF/IS-IS) + iBGP (often with route reflectors) + LDP/RSVP-TE/Segment Routing for the underlay; VPRN/VPLS/EPipe/IES for services.
• Hierarchical QoS, ISSU, MACsec, native SR make it operator-grade.
• Pair with 7705 SAR at the access tier for end-to-end SR OS deployments.