5G網路(5th generation mobile networks)是4G的次世代，並聲稱傳輸速度能高達10Gbps。
當然5G網路使用非常多的核心技術，那麼我只介紹其中一種集成技術：SDN( Software-Defined Networking )。
5G網路使用基於SD-WAN( Software-Defined Wide Area Network )軟體定義廣域網路的集成技術(嚴格來說是SDN應用在5G網路而叫SD-WAN，我認為如此)，OSI參考模型為7層架構，SDN模型為3層架構，由下而上是基礎架構層(infrastructure layer)、控制層(control layer)、應用層(application layer)。
在談這些架構前先談過去的典型結構，標準的路由器由管理板(management plane)、控制板(control plane)、資料板(data plane)構成，管理板負責HTTP、telnet、SSH等應用程式，控制板負責路由協定，如BGP、OSPF，資料板負責轉發封包，控制板在資料板之上。明顯區分控制板與資料板的關鍵是資料板無時無刻都有流量，只要路由器是開機狀態、上網狀態，然而路由並非經常性改變，甚至很少改變，如果路徑發生改變，管理路由協定的控制板才會將收斂完成的路由表更新交給資料板。
後來的SDN技術使用OpenFlow協定，將控制板從資料板拿出來再以虛擬化技術實作，路由器、交換器屬於SDN模型的基礎架構層、網管軟體屬於控制層，而控制層與基礎架構層之間的通道就使用OpenFlow溝通，並且或許docker container世代屬於其應用層。在應用層部署SD-WAN的角度來看可分電信端與用戶端，就像透過數據機上網，用戶這端叫ATU / R、ISP那端叫ATU / C，請參考圖，不過SD-WAN電信端的成本實在太高。
另外，任何網路架構都可能遇到流量瓶頸或單點失效的問題，SDN技術降低面臨這些問題的方法，叫輪詢連線。輪詢連線(session polling)是一種維持連線的特定方法並非SDN才有的名詞，並且它和思科的專利GLBP閘道負載平衡相同，都是基於Round-Robin演算法(GLBP支援3種演算法，是預設選擇Round-Robin)。另一個輪詢連線的例子，透過Linux的KVM(Kernel-based Virtual Machine)技術，使用qemu/kvm軟體進行虛擬主機遷移之前，必須在2台主機預先建立特定連線，而維持這個連線的方法，qemu/kvm就是使用輪詢連線。簡而言之就是定期向對方打招呼，確認對方沒睡著。
但是就目前來看(2018)，台灣不可能有廠商做得起SD-WAN，不但專業人士外移，台灣不太注重科技發展，IoT物聯網、big data大數據、AI人工智慧、SDN等，在台灣各間大學的資訊科系教室，普遍還能看到外面的海報寫著未來趨勢，然而這些未來趨勢在先進地區甚至已經普及。當然我們現在普遍的4G網路、手機或許在落後地區也被認為是一種先進產品。
在台灣的資訊教育沒有比較差，我不相信台商或資訊大學做不到那些核心技術。物聯網的主角是物品並連上網路，理想上我的車、冷氣、冰箱等日常生活電子物品都能連上網路，同時意味著物聯網也牽涉到很大的隱私權法律問題，然而我們較優先處理勞工問題、同性婚姻、大學校長。雖然我是在2018寫這篇文章，但在2017我就常說物聯網技術早已成熟，台灣的高度夠高卻看不到成熟的果子可摘下。
回題，我還想特別聊一下基礎架構層。據工研院文件「VLAN網路環境之SDN管理技術」描述，基於SDN的某個特定架構，聲稱能夠動態規劃路由繞送，我的理解是類似某種高度複雜化策略路由，比對到感興趣流量走路徑A、比對到其他感興趣流量走路徑B的概念。可是另一個問題是即使硬體運算力夠強大，為何殺雞用牛刀？
有些資料是說若用戶端使用2個VLAN，則電信端只能支援2000個左右的用戶，因為VTPv3支援4094個VLAN；電信端明顯是基於VRF(Virtual Routing Forwarding)虛擬路由轉發的技術來佈署L2網域，VRF通常用在MPLS(Multi-Protocol Label Switching)的PE(Provider Edge)端設備。以scalability擴展性來說，因為佈署與維護MPLS-VPN都需要純人工作業，顯得缺乏彈性，加上不易整合新舊VLAN。
在此要先弄清一個重要觀念，MPLS是一種標籤交換網路，MPLS網域通常用在電信網路；我會比喻標籤交換網路是MPLS-VPN的介質，並且MPLS-VPN是隔離客戶流量不是做加密！MPLS-VPN的分類屬於peer-to-peer VPN，而非overlay VPN！overlay VPN是電信業者僅提供線路，但是不用負責維運客戶VPN(甚至不知道有做)；然而客戶不一定有能力做VPN(或許沒有MIS)，那電信業者幫你做！這種方法主要採用MPLS-VPN。
最後介紹一個由Nokia做的實驗，youtube視頻名稱是「Nokia 5G Demonstration Video – 5G: driving the automation of everything」，
實驗內容為機器手臂分別套用4G、5G模組，並量測分別所需的延遲時間。
圖片來源(即該視頻)：https://www.youtube.com/watch?v=nNIRV8Xr19A
感謝Johnson提供。
5th generation mobile networks is 4G next generation, and claimed its bandwidth can achieve 10Gbps.
5G network has very much integrated technologies, one of them is SDN(Software-Defined Networking).
5G network use SD-WAN(Software-Defined?Wide Area Network)-based. Strictly speaking, SDN was apply in 5G network. It call SD-WAN, I think.
ISO model has 7 layers, SDN model has 3 layers. Bottom-up for SDN model is infrastructure layer, control layer and application layer.
I will discuss typical structure before SDN. Standard router is consist of management plane, control plane and data plane.
Management plane is responsible for HTTP, telnet, SSH and so on application.
Control plane is responsible for routing protocol. Such as BGP, OSPF.
Data plane is responsible for forwarding packets.
Control plane is on the data plane. Their different are include data plane always has traffic if it active state.
However routing entries was changed seldom. Control plane will updates convergence routing entries to data plane if routing entries was changed.
Later, SDN technology use OpenFlow protocol. First from data plane isolated control plane, and implement by virtualization technology.
Router, Switch are belong infrastructure layer of SDN model. Network management software is belong control plane.
The channel of OpenFlow for communication is between control layer and infrastructure layer.
And maybe docker container is belong application layer.
To deploy SD-WAN from application layer that view point. The ends are telecommunication and client. It like access Internet by modem, the client end was call ATU / R, and the ISP end was call ATU / C.
To reference image, but telecommunication end of SD-WAN that cost is too higher.
[image]
Any structure of network are meet traffic bottleneck or single point of failure problems possible.
SDN technology has the method for reduce meet the problems. It call session polling. It is specified method of keep connection, but is not proper noun of SDN.
The method is same with Cisco GLBP for default configuration. They are base Round-Robin algorithm(The GLBP has support 3 algorithms, and default algorithm is Round-Robin).
Another example for session polling, is KVM(Kernel-based Virtual Machine) technology by Linux.
By qemu/kvm software before to migrate virtual host. Must pre-establish specified connection at 2 hosts.
And method for keep the connection. The qemu/kvm use session polling.
In short, say hello to other side periodically. To confirm it is not sleeping.
But for now(2018), the corporates impossible import SD-WAN in Taiwan. Not only professional move outward, but also Taiwan is not pay attention for technological development. Such as IoT, big data, AI, or SDN.
Many classroom of university in Taiwan, outside of classroom with poster, the poster contents is "future trends".
But the future trends already to popularize at advanced area. Of course, we have 4G network now. It was be advanced product at backward area.
The IT education is not bad in Taiwan. I haven't believe Taiwan corporates or university that cannot achieve the kernel technology.
Protagonist of IoT are things. Ideally, My car, air conditioning, refrigerator that living electronic items are connect to Internet.
The means IoT has involving much legal issue for privacy. But we are first handling not important thing.
Although I have written in 2018, but I often talk IoT technology already ripe in 2017.
Come back, I want to talk infrastructure layer. According to ITRI document "SDN management of VLAN network environment".
Some SDN-based specific architecture. It claimed able to dynamic planning for routing.
My knowns is similar some very complicated policy-based routing.
If match some interest traffic select A path, or if match other some interest traffic select B path.
However, another problem. Even if computing of hardware is powerfull. Why take a musket to kill a butterfly?
Something data mean if client end use 2 VLANs, then communication end has support about 2000 clients only. Because VTPv3 can support 4094 VLANs.
Obviously, the communication end has VRF(Virtual Routing Forwarding) to deploy L2 domain. The VRF apply to PE(Provider Edge) of MPLS(Multi-Protocol Label Switching) generally.
From scalability, because to deploy and maintenance MPLS-VPN. They are need manual work purely. It is not elasticity, and not easy integrate VLANs.
First, have a important concept. MPLS is label switching network. MPLS domain was import at communication network generally.
I have metaphor. Label switching network is medium for MPLS-VPN. And MPLS-VPN function is isolated clients traffic, not to encrypt.
Class of MPLS-VPN is belong peer-to-peer VPN, not belong overlay VPN!
Overlay VPN mean the ISP provides medium, but ISP not need maintain VPN of clients(even don't know deployed)
However, client don't necessarily have ability to maintain VPN(maybe no MIS). So VPN task was given to ISP! This method is belong MPLS-VPN.
[image]
Last, I introduce a lab by Nokia. The video name of youtube is 「Nokia 5G Demonstration Video – 5G: driving the automation of everything」.
The lab content that robot arms are applied module with 4G and 5G. To measure their needed latancy time seperately.
[image]
The image source(This is the video):https://www.youtube.com/watch?v=nNIRV8Xr19A
Thanks Johnson for provided.
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