Hello,
Today, I would like to share with you an introduction to FTTx Network QoS.
1- QoS service classification
The following are the various service QoS levels set according to the current service. Looking at the table below, it can be seen that some levels do not correspond to services. The main consideration is to add service reservations with different guarantee requirements in the future.
Services type | Priority |
Network management | 6 |
Voice | 5 |
Special line | 4 |
CATV | 3 |
Broadband（PPPOE） | 0 |
2- Overall network E2E QoS scheme
The network-wide QoS solution adopts the Diff-serv model, which ensures the QoS requirements through the QoS parameter information carried in the packet header. There are two directions: up and down.
For IP voice, IPTV and private line services, bandwidth is guaranteed through bandwidth planning, bandwidth management, and priority marking. For broadband services, best-effort forwarding is adopted, while the maximum bandwidth of each broadband user is limited.
QoS of uplink service:
HG/ONT/MDU ensures that services with high QoS requirements are forwarded first according to the binding relationship between ports and different services. The forwarding priority is from high to low: IP voice/network management --> leased line --> IPTV --> broadband.
The ONU/OLT distinguishes services (data, voice, video, government-enterprise private line services, etc.) according to different PVC and VLAN IDs, and then identifies the VLAN and 802.1p priority of each service by referring to the VLAN/service priority planning and mapping table. Priority scheduling is performed between ONU-OLT-L2-MSCG/BAS/SR according to 802.1p.
Enable the simple traffic classification function on the MSCG/BAS/SR entry to identify the 802.1p values of different service packets. The device classifies the ingress traffic according to the QoS requirements of the service flow, and re-marks the packet flow as needed, so that the devices in the network can use the new marking value as the classification standard: For the native IP method, MSCG/BAS needs to give priority to 802.1p Mapping to IP layer DSCP value; for VPN access mode, MSCG/BAS/SR needs to map 802.1p to MPLS EXP.
Backbone routers above MSCG/BAS/SR perform congestion management, congestion avoidance and outbound port speed limit according to the DSCP value of IP or the EXP priority of MPLS.
QoS for downlink services:
IPTV, IP voice, and broadband services pass through their respective egress switches or PE devices, and set the DSCP/MPLS EXP of their respective service packets according to the different priorities of different services. Refer to the preceding service priority planning and mapping table. The backbone network performs priority queue scheduling and forwarding according to DSCP/MPLS EXP.
For below POP, downlink traffic is delivered through MSCG/BAS/SR. Since IPTV unicast services, IP voice services, and government-enterprise private line services are carried at the backbone layer in L3 VPN mode, and broadband services are carried in Native IP mode, after downlink service packets arrive at MSCG/BAS/SR, MSCG/BAS/SR will Map DSCP/MPLS EXP to 802.1p, and perform priority scheduling and forwarding between MSCG/BAS/SR and L2/OLT/MDU/ONU/HG according to 802.1p.
The entire network of BTV services is carried in Native IP mode. Layer 3 forwarding is performed on the backbone network according to the DSCP priority, and Layer 2 forwarding is performed according to the 802.1p priority below the MSCG/BAS. MSCG/BAS completes the mapping from DSCP to 802.1p.
Different service VLANs are different. MSCG/BAS/SR can perform CAR according to the service VLAN, or perform CAR on the access device for different service flows. The specific settings can be made according to bandwidth planning.
For broadband services accessed by PPPoE, different maximum accessible rates can be authorized according to AAA, such as: 512K, 1Mbps and 2Mbps, and the MSCG controls the access bandwidth of each broadband user.
For BTV services, if the video stream jitters due to a problem on the server or line side, you can perform Shaping on the MSCG/BAS to shape the traffic.
The queue scheduling policy adopts PQ or PQ+WFQ. For the weight of each queue in WFQ, refer to the service bandwidth planning.
3- FTTx network QoS policy
As the end of the entire E2E bearer network (ONU/OLT), it plays an important role in "connecting the previous and the next". xPON equipment adopts the principle of "do not trust user-side messages, but trust network-side messages".
The specific QoS policies are as follows:
Traffic classification: Classify traffic flow based on VLAN.
Mark:
In the upstream direction, flow-based priority re-marking, flow-based CAR, queuing policy and queue scheduling based on the re-marked 802.1p priority;
In the downstream direction, flow-based priority replication, flow-based CAR, 802.1p priority-based queuing policy and queue scheduling. The CAR needs to be determined according to the maximum possible traffic of the service, and the queue scheduling policy adopts PQ scheduling.
Traffic policing: implement CAR rate limiting through traffic templates or ports (optional, if the upper-layer device supports rate-limiting, to simplify the configuration, it is recommended to limit the rate on the upper-layer device).
Congestion management: high-priority services use PQ scheduling mode, and low-priority services use WRR scheduling mode.
DBA: EPON implements DBA speed limit based on ONU, and each ONU is configured with a DBA template of type 3 (guaranteed/non-guaranteed), which can guarantee high-priority services and share bandwidth; GPON implements DBA limit based on service types Configure different levels of Tcont according to different services. For example, the TDM service requires a high level and the configuration type is Type1 (Fix).
You are welcome to leave a message and exchange in the comment area. Thank you!
