Hi everyone.
With this first post, I am beginning a seriesof informational posts that will help you to selfstudy int the search of the SDN´s Certification.
Is importat taht you know that each one post is indexed, that is mean, you´ll find a link to go to the next or to the backward post
So, lets begin.
1
CHALLENGES AND CHARACTERISTICS OF TRADITIONAL NETWORKS
Traditional Networks Characteristics.
Due to reliability and high availability, the current network are based on distributed networking approach, where every device is configured independently; each of them performs calculation independently and administratively.
Lets see the picture as an example:
ü imagine a traffic enter from PEA and exit at PEB. When PEA receive the traffic, PEA will check according to routing table.
ü Based on routing table, it decides that in order to reach PEB, it have to go through PEC as next hop.
ü Then PEA forward the traffic to PEC. PEC does exactly the same thing as PEA; check routing table, finding the next hop and forward to PEB. This forwarding manner called per-hop forwarding. Information inside routing table is collected and built through static routing or dynamic routing.
ü In large scale network, normally routers are running dynamic routing protocol such as OSPF and ISIS. Every router in the routing domain collect link state information and then perform independently by using the same routing algorithm, for example, Shortest Path First Algorithm to find the shortest route. This networking called as distributed networking.
Traditionally, control plane and data plane reside in the same physical hardware.
o The internal architecture of a network devices has three planes of operation:
§ Management Plane handles external user interaction and administrative tasks like authentication, logging, and configuration via a Web interface or CLI
§ Control Plane performs the internal device operations, provides the instructions used by the silicon engines to direct the packets; it also runs the routing and switching protocols and feeds operational data back to the management plane.
§ Data Plane is the engine room that moves packets through the device, using the forwarding table supplied by the control plane to determine the output port.
Traditional Networks Challenges- an Overview
Diagram above generally concludes the 3 main challenges and limitations faced by conventional network nowadays, listed as:
· Network inflexibility
· Network complexity
· Slow network provisioning and innovation
Now, lets follow with the examples:
Network Inflexibility due to shortest path first calculation mechanism.
For the first part of the figure, based on shortest path first algorithm, traffic from Router A to Router B will take link between A-B. At the moment, link bandwidth usage has been occupied around 6G over 5G links, in which are link bandwidth usage are over-utilized, whereas link A-C-B is under-utilized. Even though MPLS TE has been introduced to solve under-utilized link usage, but most of MPLS TE planning are pre-configured and does not solve real-time or sudden burst traffic, hence causing network congestion.
For second part of figure, there are some certain requirement. For example, there are 3 tunnel to be establish in sequence. First tunnel requirement needs 6G from A to E, hence after calculation or explicit configuration, it might be take A-B-C-D-E path. Followed by second tunnel with requirement 4G from C to G, eventually take the path C-B-A-F-G. For the third tunnel with requirement 8G from C to D. As a result, due to insufficient bandwidth, it fails to be established.
Traditional distributed networking approach causes many control plane protocols to be deployed and configured on a devices, including IGP protocol, BGP protocol, MPLS protocol, ipv6 protocol,etc.
IETF has produced thousands of protocol standardization to describe various network protocol features and the numbers of standardizations are still increasing from time to time when there are new features and network functions being developed and implemented.
This makes a networking engineer has to learn complicated technology and need to master certain knowledge in order to perform network operation and maintenance.
On the other hands, some vendors may deploy private proprietary protocol in operator network, causing a further difficulty in operation and maintenance. Difference vendor networking devices such as Huawei, CISCO, juniper provide different type of GUI, causing networking engineer has to learn multi-vendor on how to operate the networking devices.
In order to cope with the aggressively increasing network requirement, network expansion and increasing numbers of protocols and features deployed in the network will definitely increasing; Various types of network protocols and features have to deployed in order to cater for different network requirements.
The example shown on the slide above clearly shows the complexity of network O&M and configurations in traditional network; for instance, to configure a L3VPN service in network, the steps of configuring IGP protocol, configuring MPLS, configure L3VPN instance, configure routing protocol between PE and CE and configuring MP-BGP peer; these series of configurations need to be done on all provider edge (PE) routers which are connected to customer edge (CE) routers.
The configuration scripts shown on the right shows a complete configurations command deployed on PE3, just to configure a L3VPN service, and the command involved is a lot.
The example given above is based on the assumption that PE devices connected are all Huawei devices. Configuration work will become even more complicated if it is applied to the scenario that different vendors devices are used in the network; for examples, some PE devices are belonged to Cisco while some belongs to Huawei’s. The network engineer needs to be familiar on Cisco configuration platform and also Huawei configuration platform in order to complete the end to end configuration in this case.
Another major issue brought by the distributed networking architecture is the slow network innovation and slow network provisioning. This can be proven to see that there are very less new service innovation is completed since the past 30 years. The service features, such as L3VPN and L2VPN are the conventional features which have been developed long ago. Why is this scenario happening?
In the process of defining a new service feature or service type, this service features must be standardized first before proceeding with further development. Thus, the service requirement will first needs to be sent to IETF, to standardize the feature standard.
This process normally takes up 1 to 2 years for definition discussion before the standards about this feature is released officially; Standardization is very crucial in the step to ensure multi-vendor inter-operability; as all vendors will do research and survey on this features based on the standard released.
Each vendor will then need at least one year to embed this features into vendors’ devices once R&D has successfully developed the features based on IETF standards; Devices then can be upgraded to support this particular features; after this, deployment and configurations need to be planned and performed too, to make this particular service goes online.
The whole process will require 3 to 5 years duration and this long duration definitely cannot fulfill the service requirement from the network operator; this needs to be solved as soon as possible to guarantee operator’s satisfaction.
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Thank a lot for your reading. I hopw that you found this information concise, clearly and helpful.
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