Overlay Routing Problem StatementHuaweiD2-03,Huawei HeadquartersShenzhenChinadengshangling@huawei.comHuaweiHuaWei Bld., No.3 Xinxi Rd.BeijingChinaligeng23@huawei.comTsinghua University4-104, FIT BuildingBeijingChinacuiyong@tsinghua.edu.cn
General
Internet Engineering Task ForcetemplateThis document considers the limitations of existing technologies in addressing
the challenges of low network latency. It analyzes the problem of signaling redundancy
on control plane and problem of non-global optimal path selection policy for overlay
network and explores possible solutions.IntroductionThere are emerging mobile applications, such as online games, audio and video,
and AR (augmented reality)/VR (virtual reality), which have higher requirements for
low latency, throughput, and packet loss. With the rapid development of mobile Internet
services, the research on mobile Internet architecture has become a hot topic.
The terminal industry, represented by device-edge-pipe-cloud devices with ultimate
interoperability experience in all-scenario, poses great challenges to the current
Internet and requires disruptive technologies to support transformation.
This document analyzes some existing technologies related to improving the user
experience of real-time applications, and hope to find a solution to improve the
end-to-end transmission experience to meet the increasing requirements of network delay.
Related WorkThere is a significant amount of previous work in terms of improving the
end-to-end transmission performance. Some are to control the destination ends,
and some are to control the network path. The relevant work is presented in
this section.Global Server Load Balancer Based on Smart DNSIn the request process of Global Server Load Balancer (GSLB) Based on Smart DNS,
the root DNS forcibly forwards the DNS to the GSLB device. The GSLB resolves the optimal
IP address based on the server load and the user's IP address, sends the DNS response
to the local server, and finally sends the response to the user.GSLB based on smart DNS enables an application to control the destination of requests
but cannot control the path to the destination. For example, if an application wants to
further optimize the path requested by a user due to security or performance considerations,
smart DNS cannot meet the preceding requirements.The overlay network technology can further optimize the path to avoid failure or congestion
in the path to a certain extent. It is an important means to improve the quality of Internet
transmission and user experience and achieve high-quality transmission.Intelligent Overlay RoutingThe Internet consists of multiple carriers, ISPs, and autonomous domains, which causes the
complex business relationships between domains. The transmission paths of the Internet are affected
by business relationships and is not the shortest path in the network. For example, transmission between
two Asian nodes may be detoured to Europe. This increases the end-to-end latency. At the same time,
the Internet routing is not aware of path performance, and thus it is difficult to avoid failure or
congestion in the path, or requires a long convergence time.The overlay network technology is proposed to find out the optimal path of the Internet.
Software forwarding units are deployed in data centers in different areas of the Internet to connect
to each other and schedule each other. In this way, a new virtual overlay network is constructed on the
basis of the existing public network (underlay network). An intermediate forwarding node may be referred
to as a forwarding relay or a point of presence (PoP) node.Intelligent overlay routing, the key of overlay network technology, directly determines the
transmission performance for users accessing the overlay network. It selects appropriate forwarding
nodes on the overlay network to form an end-to-end optimal forwarding path for data transmission.In the existing intelligent overlay routing technologies, the optimal path is determined by
three subsystems: the ingress PoP selection system, the egress PoP selection system, and the internal
overlay routing system. The optimal scheme is computed independently in each subsystem, but the local
optimal doesn’t mean the global optimal. The sum of each optimal scheme in subsystem can’t figure out
the best network path. In addition, it takes expensive cost to maintain the routing table status and
invoke different systems to perform packet header encapsulation and decapsulation for subsystems.Challenges and Problem StatementThis section describes in detail some possible bottlenecks encountered when dealing with low network latency.Signaling Redundancy on Control PlaneOverlay routing can be divided into two segments: access segment and backbone segment. The source in
the access segment obtains the address of the access controller through the DNS and requests the address
of the access point (ingress or egress). The access controller selects an access point based on factors
such as geographic location and latency. The backbone controller in the backbone segment updates the
optimal path from any ingress to egress in real time.On the control plane, the source obtains the address of destination and access
controller through the DNS, requests for an access point from the access controller,
and sends the messages to the destination. Multiple rounds of signaling interaction
with the DNS and the controller are required from connection establishment to packet
transmission. As shown in the figure, five rounds of signaling interaction are needed and it is redundant.Non-global Optimal Path Selection PolicyIn the prior art, an optimal path is calculated in several parts. That is,
the Internet gets the optimal routing in access segment and backbone segment,
and strings them together as the optimal path. However, the optimal path calculated
in this way is not an optimal end-to-end path.For example, the nearest PoP would be chosen as the access point (ingress/egress)
according to the latency. Take A as the source and C as the destination, and then an
optimal path is calculated by the existing overlay routing technology: A->D->E->F->C (263.7ms).
However, it is clear that there is a better path here: A->B->C (140.4ms).Candidate Solution DirectionsThis section seeks for the possible breakthrough point to achieve lower latency and improve the user experience in real-time applications.As mentioned above, the problem of signaling redundancy on control plane and problem of non-global
optimal path may be the obstacles to reduce lower network latency and improve user’s experience.
A possible solution direction is presented below.To solve the problem of non-global optimal path, the source calculates the global optimal overlay path and delivers to the destination. For details, the source directly delivers routing through DNS. The DNS is redirected to the controller
to request an optimal path, and the controller returns a multi-dimensional path vector. In this way, the users can
control a delivery path at the source. Also, the intermediate forwarding nodes don’t need to maintain any routing
table, because all routing status information may be included in a private header of a data packet generated by the source.IANA ConsiderationsRequest to IANA will be added later.Security ConsiderationsSecurity issues will be considered later in the design.ReferencesNormative ReferencesInformative ReferencesAdditional StuffThis becomes an Appendix.