Nokia 7705 SAR-8 v2 — the cell-site / aggregation edge router

The 7705 SAR (Service Aggregation Router) family is Nokia's compact, hardened MPLS edge router. Targeted at mobile backhaul, transport-aggregation, and small service-node deployments — anywhere you need a full SR OS feature set in a small, often outdoor-rated chassis. The SAR-8 v2 (8 service slots) is the medium-sized chassis you'll most often touch in regional aggregation networks.

What it actually is

| Property | SAR-8 v2 | |---|---| | Form factor | 4 RU, 19" rack | | Service slots | 8 (MDA — Media Dependent Adapters) | | Control / fan modules | 1 + 1 redundant CSM (Control / Switching Module) | | Typical interfaces | Mix of GE, 10GE, and legacy serial / TDM via MDAs | | OS | SR OS (Service Router Operating System) — same OS as 7750 / 7950 | | Operating temp | -40 °C to +65 °C (extended) for outdoor cabinets | | Power | DC or AC variants |

It runs the same SR OS as the big 7750 platform — every command you learn here transfers up the stack. That's a big part of the value: one CLI, one config syntax, from the cell-site to the core.

Where it lives in the network

Two typical deployments:

1. Mobile backhaul / cell-site router (CSR). Sits at the foot of a cell tower (or in a hut nearby), aggregating GE/10GE radios from the eNB/gNB, terminating them as MPLS pseudowires back to the BSC/EPC over a regional fiber ring.
2. Small enterprise / industrial aggregation. Sits at a regional aggregation point, terminating low-speed customer access (often serial / TDM via specialty MDAs) into an MPLS service layer.

In both, the SAR-8 sits between access (toward radios or customer interfaces) and transport (toward the operator's MPLS core, usually 7750-class PEs).

A typical config — IES uplink + EPipe to remote site

[object Object]

[object Object]

This brings up an MPLS pseudowire between the cell-site SAR-8's 1/2/3 SAP and the corresponding SAP on the central 7750. From the radio's perspective it's a transparent Ethernet wire to the controller.

What to know operationally

• Timing is often as critical as connectivity. Mobile networks need sub-microsecond phase/frequency sync. SAR-8 supports PTP (1588v2) master/slave, SyncE, and BITS T1/E1 — get the design's timing source straight before commissioning.
• CSM redundancy. Two CSMs give active/standby; failover is sub-second for the data plane (MDAs keep running) but a few seconds for the control plane. Important for HA designs.
• Common MDAs for the user's environment: 4-port GE/10GE, 8-port Fast-E, 16-port T1/E1 (TDM pseudowire), 4-port channelized OC-3/OC-12 (legacy SONET).
• Power and environment. When deployed in an outdoor cabinet, the DC-input variant + extended temperature rating matter. Check the BTU/heat budget against the cabinet's cooling.

Useful 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

• 7705 SAR = compact SR OS edge router, same CLI as 7750 — the same commands transfer.
• Common roles: cell-site router for mobile backhaul, aggregation edge for low-speed industrial access.
• MDA-based I/O — pick the MDA per slot per interface mix.
• Timing (PTP / SyncE / BITS) often defines the deployment; don't treat it as an afterthought.
• Pair with a 7750 SR at the core for end-to-end MPLS services.