BFD uses Hello intervals, poll interval and multiplier for detection.<\/p>\n\n\n
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<\/a><\/figure><\/div>\n\n\nApplication Aware Routing\/Enhanced Application Aware Routing<\/h2>\n\n\n\n
I have already written a Blog about EAAR (http:\/\/jaychou.co.uk\/?p=613<\/a>) – This section is based on standard AAR.<\/p>\n\n\n\n A better example to understand AAR is having a scenario where there are multiple Transports such as Biz-Internet, Internet and LTE. Should there be an issue with one of the Transports which will impact the user experience. With AAR, you create a threshold for a specific Application so should the transport not meet SLA then it will switch to another Transport (fastest is 10minutes unless using EAAR which is 10s).<\/p>\n\n\n\n AAR is measured against Latency\/Jitter\/Loss, when the user configures the Application Aware Routing Policy then you can set the threshold before the transport switches over. This ensures the SLA is compliant through the SD-WAN fabric. <\/p>\n\n\n\n BFD is used for AAR, which has two timers:<\/p>\n\n\n\n FEC uses the XOR cipher. If the Cipher is the same then no change has been made. An example of XOR operation below:<\/p>\n\n\n This helps to understand how FEC is operated, XOR allows FEC to create a parity packet which then reconstructs the lost packet.<\/p>\n\n\n\n FEC helps the following :<\/p>\n\n\n\n FEC can only reconstruct 1 packet out of 4.<\/p>\n\n\n\n As the name suggests, this allows duplcating packets for critical traffic\/application such as Credit or ATM transactions and sending the duplicated path over a second path.<\/p>\n\n\n\n This can work when there is little or limited of Critical traffic compared to the capacity of the network. If there is multiple circuits then SD-WAN will choose the best transport. Best as in the least amount of packet loss to replicate the packets to.<\/p>\n\n\n When transferring, duplicate the packets of the primary tunnel and send simultanousely, the secondary\/duplicated tunnel is chosen based on MTU. Duplication happens only if the secondary tunnel MTU is greater or equal to that of first to avoid fragmentation. When the receiving router receives the first packet to the LAN whether it is duplicate or original it will drop the other one.<\/p>\n\n\n\n Is used when Shaping is being utilised. This allows the packets to sit in a queue waiting to be sent in the egress interface. Uses Weighted Round-Robin, when the queue gets dropped it uses Random Early Discard. <\/p>\n\n\n\n Is used when you do not want to drop the packet if there is a queue and exceeded the configured Shaper rate. Essentially if there are no more tokens in the bucket it will be placed in a queue. The queued packets will operate in Weighted Round-Robin. This is not supported on Sub-interfaces.<\/p>\n\n\n Is used if you want to completely drop the traffic if does not conform the policer rate. <\/p>\n\n\n You can bond both transport links together – this essentially means it will be per packet load sharing, with the receiving host ordering the packets if packets are being send out of order.<\/p>\n\n\n\n None-conforming traffic will spill over to a different circuit.<\/p>\n\n\n DSCP operates on Layer 3, so as a packet is being mapped into a forwarding class, you can modify this to another DSCP rule.<\/p>\n\n\n You can remark COS (Layer 2) frames.<\/p>\n\n\n Each WAN Edge router sends BFD Hello packets for path quality and liveliness detection, the packets will be echoed back by the receiving router. Using Hello interval and multiplier will determine how many BFD packets need to be lost in order to declare whether the IPsec tunnel is down.<\/p>\n\n\n\n The number of hello intervals that fit inside the Poll interval determins the number of BFD packets considered for establising poll interval average path quality. This is used to help the need in fragmentation of packets, Routers on the WAN edge will signal the appropriate MTU based on the host\/application on the LAN. This in turn will be forwarded to the receiving router in terms of the appropriate MTU it needs to be.<\/p>\n\n\n This allows the site to dynamically adjust the sending rate of its traffic to acomodate lower bandwidth circuits at remote sites.<\/p>\n\n\n\n Cloud on Ramp allows quality probing towards popular SaaS Application, the WAN Edge router chooses the best porforming path towards the popular Saas Applications.<\/p>\n\n\n CoR works by using the following 3 components:<\/p>\n\n\n\n An example is if you had two DIA transports to the SaaS application, CoR monitors the edge to the SaaS application. This in turn then picks the best porforming metrics such as loss and delay.<\/p>\n\n\n\n Perfomance Visiibilty works by the WAN edge reuesting DNS in VPN0 and sends a DNS reuest for the pre-configured SaaS application.<\/p>\n\n\n\n DNS requests are duplicated and sent to all transports to get the application server address.<\/p>\n\n\n\n HTTP pings are sent to the application such as SalesForce servers on both the DIA links for performance measurements.<\/p>\n\n\n The results and score is measured from 0-10 with 10 being the best. <\/p>\n\n\n\n 0-5 RED<\/p>\n\n\n\n 5-8 Yellow<\/p>\n\n\n\n 8-10 Green<\/p>\n\n\n\n TCP optimisation fine tunes the processing of TCP traffic which in turn decreases the round-trip latency to improve throughput.<\/p>\n\n\n\n An example is if you are using a high latency link like a satelite transport attempting to connect to a SaaS based or Server, the TCP handshake is formed from Client to the Router. This TCP connection will be terminated and in turn the router will then form another TCP handshake with the remote router. This TCP handshake from WAN Edge to WAN Edge will be cached. The remote router will form a TCP handshake with the Server.<\/p>\n\n\n Essentially using NBAR2 to classify and regonise applications, it uses DPI plus different techniques such as:<\/p>\n\n\n\n AppQoE’s main goal is to improve application Quality of Experience. AppQoE Features in SD-WAN BFD BFD is used for path liveliness and to measure the quality of the link. Whether the link is up\/down, loss\/latency\/jitter BFD runs between the WAN Edges as well as the Edge Cloud routers. BFD uses Hello intervals, poll interval and … Continue reading SD-WAN AppQoE<\/span> \n
Forward Error Correction (FEC)<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\n\n
Packet Duplication<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nQoS<\/h2>\n\n\n\n
Queuing <\/h2>\n\n\n\n
Shaping <\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nPolicing<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nLink Bonding<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nDSCP Marking an Remarking<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nCOS (802.1p) Marking and Re-marking<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nPath Quality and Liveliness Detection<\/h2>\n\n\n\n
The App Route multuplier determines the number of poll intervals for establishing the ocerall average path quality.<\/p>\n\n\n<\/a><\/figure><\/div>\n\n\nTCP MSS Adjust<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nPer-Tunnel QoS support on SD-WAN<\/h2>\n\n\n\n
Cloud onRamp for SaaS<\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\n\n
<\/a><\/figure><\/div>\n\n<\/a><\/figure><\/div>\n\n\nTCP Optimisation <\/h2>\n\n\n\n
<\/a><\/figure><\/div>\n\n\nSD-AVC – Advanced Visibilility Control<\/h2>\n\n\n\n
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