Carrier Ethernet quality of service for an Ethernet virtual private line

Platform: Nokia SR OS 22.10 · Role: Ethernet service edge · Last reviewed 2026-09-22

Role in the network

An Ethernet virtual private line is sold as a bandwidth profile: a committed information rate the customer is guaranteed, an excess information rate they may burst into, and a frame loss, delay and delay variation objective per traffic class. The configuration has to make the network behave the way the contract says, which means policing on ingress so the customer cannot exceed what they bought, shaping on egress so the handoff matches the far end's capability, and a consistent class map so a frame marked for voice treatment at one end is still marked for voice treatment at the other.

Service definition

Bandwidth profile and class objectives for this example service.
Class	Marking	Committed rate	Objective
Real time (voice and signalling transport)	DSCP EF, dot1p 5	20 Mbps	Loss <0.01%, delay <10 ms, jitter <3 ms
Interactive	DSCP AF31, dot1p 3	40 Mbps	Loss <0.1%, delay <25 ms
Bulk	DSCP AF11, dot1p 1	40 Mbps	Loss <0.5%
Best effort	DSCP default, dot1p 0	Remainder, burst to 200 Mbps	No objective
Service total: 100 Mbps committed, 200 Mbps excess, on a 1 Gbps user network interface

Configuration

# ---------------------------------------------------------------------------
# Ingress classification. Customer dot1p is trusted for classification only;
# the network re-marks to its own internal forwarding class so a customer
# cannot promote their own traffic past another customer's.
# ---------------------------------------------------------------------------
configure qos sap-ingress 1001 create
    description "EVPL 1001 - 100M CIR / 200M EIR"
    queue 1 create
        rate 200000 cir 100000
    exit
    queue 2 best-effort create
        rate 40000 cir 40000
    exit
    queue 3 expedite create
        rate 40000 cir 40000
    exit
    queue 4 expedite create
        rate 20000 cir 20000
    exit
    fc "be" create
        queue 1
    exit
    fc "af" create
        queue 2
    exit
    fc "l1" create
        queue 3
    exit
    fc "ef" create
        queue 4
    exit
    dot1p 0 fc "be" priority low
    dot1p 1 fc "af" priority low
    dot1p 3 fc "l1" priority high
    dot1p 5 fc "ef" priority high
    dscp be fc "be" priority low
    dscp af11 fc "af" priority low
    dscp af31 fc "l1" priority high
    dscp ef fc "ef" priority high
exit

# ---------------------------------------------------------------------------
# Egress shaping and re-marking. The aggregate shaper is what keeps the
# handoff inside the contracted rate; without it a burst arriving from the
# core is dropped by the customer's equipment instead of by ours, and the
# loss shows up in their measurement and not in our own.
# ---------------------------------------------------------------------------
configure qos sap-egress 1001 create
    description "EVPL 1001 egress shaping and remarking"
    queue 1 create
        rate 200000 cir 100000
    exit
    queue 2 create
        rate 40000 cir 40000
    exit
    queue 3 expedite create
        rate 40000 cir 40000
    exit
    queue 4 expedite create
        rate 20000 cir 20000
    exit
    fc "be" create
        queue 1
        dot1p 0
        dscp be
    exit
    fc "af" create
        queue 2
        dot1p 1
        dscp af11
    exit
    fc "l1" create
        queue 3
        dot1p 3
        dscp af31
    exit
    fc "ef" create
        queue 4
        dot1p 5
        dscp ef
    exit
exit

# ---------------------------------------------------------------------------
# Aggregate rate across the whole service access point, applied on top of the
# per-queue rates. MEF 10.3 bandwidth profiles are per class of service
# identifier; the aggregate enforces the envelope.
# ---------------------------------------------------------------------------
configure qos scheduler-policy "EVPL-100M" create
    tier 1
        scheduler "aggregate" create
            rate 200000 cir 100000
        exit
    exit
exit

# ---------------------------------------------------------------------------
# The Ethernet pseudowire service itself: a point to point VLL between this
# node and the far-end node across the MPLS core.
# ---------------------------------------------------------------------------
configure service epipe 1001 customer 5 create
    description "CUST-ACME EVPL site 1 to site 2"
    service-mtu 1522
    sap 1/1/3:1001 create
        description "UNI - CUST-ACME site 1"
        ingress
            qos 1001
            scheduler-policy "EVPL-100M"
        exit
        egress
            qos 1001
            scheduler-policy "EVPL-100M"
        exit
        # Link-level OAM per IEEE 802.1ag for service continuity monitoring.
        eth-cfm
            mep 101 domain 1 association 1001 direction down
                ccm-enable
                low-priority-defect all-def
                no shutdown
            exit
        exit
    exit
    spoke-sdp 5:1001 create
        description "Pseudowire to site 2 PE"
        no shutdown
    exit
    no shutdown
exit

Verification

Command	Expected result
`show service id 1001 base`	Service `Up`, service access point and spoke pseudowire both operational.
`show service id 1001 sap 1/1/3:1001 stats`	Per-forwarding-class counters incrementing; in-profile and out-of-profile octets separated, which is the proof that the policer is classifying rather than just counting.
`monitor service id 1001 sap 1/1/3:1001 rate`	Offered rate clipped at 200 Mbps under a flood test, and no drops in the expedited queues while best-effort is being discarded.
`show eth-cfm mep 101 domain 1 association 1001`	Continuity check messages received, no defect flags set.
`oam eth-cfm two-way-delay-test`	Round trip delay and delay variation inside the contracted objective for the real-time class.

Operational notes

Service MTU. 1522 accommodates a 1500-byte customer payload plus the service VLAN tag. If the customer double-tags, raise it to 1526 and re-check the core MTU, or frames will be silently dropped at a midpoint that does not report it.
Do not trust customer markings end to end. Classify on ingress, re-mark to the network's own scheme, re-mark again on egress toward the customer. A network that forwards customer DSCP untouched cannot honour a per-class objective.
Measure where the contract is measured. Frame loss ratio is defined at the user network interface. Counters taken in the core will look better than the figure the customer can measure, and the gap is where disputes come from.
Colour awareness. This reference is colour blind: committed and excess are decided by the policer. A colour-aware profile using the drop eligible indicator bit is required if the customer pre-marks excess traffic themselves.

Standards

MEF 10.3 — Ethernet services attributes, the source of the committed and excess information rate definitions.
MEF 6.2 — Ethernet services definitions, including Ethernet virtual private line.
IEEE 802.1Q — VLAN tagging and priority code point.
IEEE 802.1ag — Connectivity fault management.
ITU-T Y.1731 — OAM functions and mechanisms for Ethernet-based networks, the delay and loss measurement used above.
ITU-T G.8032 — Ethernet ring protection switching, where the access ring requires sub-50 ms protection.
RFC 2474 and RFC 2597 — DiffServ field and assured forwarding classes.
RFC 3246 — Expedited forwarding per-hop behaviour.
RFC 4448 — Encapsulation methods for Ethernet over MPLS.

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