Mesh network may become the ideal bearer network topology to meet operators’ requirements for high-quality network while solving the design and construction problems.
As the underlying transmission platform of the entire communication network, the advantages and disadvantages of the bearer network topology are very important, directly affecting the transmission security and bandwidth delay of the entire network.
Some bearer network planning and construction personnel, SPN/IPRAN and other mainstream bearer network topology network specifications, design rules are too much complexity, quite a few words. Such as the ring rate, each layer of the long ring rate, double return or not, the ring and across the ring on the other side of the route can not be the same, oversized aggregation nodes, and so on.
Complex specification rules, making the design more difficult, there are also indicators of conflict. However, operators attach importance to the network specification is not wrong, through the establishment of a variety of networking indicators to guide the construction of the network, naturally, I hope that the more perfect and detailed the better, which also gives rise to a more ideal topology networking requirements.
History Of The Development Of The Bearer Network Topology
First, we review the changes in networking methods, major equipment and upper layer services since the birth of optical networks:
The rapid expansion of the bearer network scale is an important reason for the continuous change of topology organization.
As operators begin to emphasize cost-effective network construction, precise planning and wireless C-RANization, the growth trend of bearer network scale for supporting wireless is beginning to slow down. Therefore, the topology architecture needs to comprehensively consider performance quality, cost and service requirements.
Another guide about everything about bearer networks.
The technical characteristics of the above typical topologies are analyzed in detail below:
1. Line shape
- AZ single, not adapted to large-scale large number of service transmission needs.
- No protected path.
2. Star shape
- Single A and multiple Z, suitable for single-core multi-branch business model.
- No protection path, core node failure business full block.
3. Tree shape
- Equivalent to the series connection of multiple star shapes, can quickly realize a larger range of network coverage.
- No protection path, single node failure of core/sub-core business impact.
4. Ring shape
- Multiple A’s and Z’s with protection paths.
5. Hierarchical Ring
- A variant of ring-shaped networking, with multiple aggregation rings under the core layer and a large number of access rings under the aggregation layer, adapting to large-scale networking and taking into account security and economy.
6. Mouth shape
- Each node in the two-point ring adds a standby node, with the advantages of ring path protection, but also to prevent the risk of node failure, higher cost, applicable to large-scale networking core layer.
- Zigzag also has the advantage of easy horizontal expansion, compared to adding/subtracting nodes in the ring, the expansion has less impact on the network in use
Starting from the ring network, the scale and security of the bearer network began to have a qualitative improvement, and the demand for fiber optic cables has not increased significantly.
For example, the use of star networking 1 + 5 points needs 5 optical fibers, ring networking, although the need for 6, but ring networking can follow the actual routing of fiber optic cables towards the deployment of nodes in the ring, if the use of star networking, then go in the same direction of the fiber optic cables, overlapping fiber segments lead to fiber core consumption will increase several times.
However, there are also difficulties in organizing the ring. For example, in order to avoid the same routing ring requires the ring of each fiber optic cable segments can not be the same path, otherwise, once the segment is interrupted, the ring will inevitably appear node isolation and thus interruptions, convergence ring is especially not allowed to occur.
As the general direction of fiber optic cables and roads, various counties, townships and districts do not necessarily have more than one road as well as with the road cable, resulting in the convergence of the ring at the end of the node back to the first node of the fiber optic cable segments are often no independent routing cable available.
Do not allow the same routing ring is one of the important networking specifications mentioned in the previous section, similar networking rules are too many and too complex, basically related to ring and hierarchical ring networking system.
Ring networking development has been the absolute mainstream. But the complexity of the actual cable room, the face of diverse and even dynamic bandwidth requirements such as tidal flow, new services 5G toB demanding reliability requirements and network intelligence development direction, the limitations of the ring network began to become obvious, perhaps to the time to change a change.
Advantages And Disadvantages Of Mesh Networks
Mesh network topology is a network structure in which each node in the network is directly connected to other nodes. This structure provides a high degree of redundancy and reliability because each node has multiple paths to other nodes.
In a mesh network topology, data can be transmitted through multiple paths so that in case of failure of some connection or node, the data can still reach its destination through other paths.
The above standard mesh network also known as Full Mesh network has many advantages but is costly, whereas non-Full Mesh is cost controlled, adaptable to complex environments, and can evolve smoothly to Full Mesh.
Non-Full Mesh networking means that the nodes in the network are not all directly connected, but are interconnected through some nodes that act as intermediaries or central nodes. This structure can be in various forms such as Hub-Spoke, Partial-Mesh, hierarchical topology, etc.
Early transmission network theory, it was mentioned that the Mesh network is the most ideal transmission network, but the development of optical networks for more than 30 years, the equipment has been updated for several generations, so far has not become the mainstream, the reasons for its advantages and disadvantages related.
Advantages Of Mesh Networks
Compared with ring dual route protection, the available routes of Mesh network are at least three, and Full Mesh can even be regarded as full routing.
Moreover, with more routes, not only the security is improved, the bandwidth is also increased, optional routes more intelligent traffic engineering means such as peak-fill-valley, path balancing to have a basis for implementation and significance.
Secondly, Mesh networking does not need to consider the direction of the fiber optic cable, can be fully connected to the full connection, not on the best efforts. Unlike the thin ring across the ring to borrow a lot of factors to consider such as the availability of fiber optic cables, length, and whether the bandwidth will be crowded, etc., mesh networking naturally has the advantage of borrowing and sharing.
Therefore, the mesh structure is simple to design, and it is easier to realize the requirements of ring formation, double return ring, long ring and other indexes under the ring network – controlling the size of each mesh hole and giving each node as many routes as possible.
In addition, the underlying fiber optic cable room is more flexible and simple to plan with mesh-oriented. A properly planned mesh network can shorten paths and avoid the increased latency caused by loopbacks in ring or tree networks, which is beneficial to latency-sensitive services.
Cons Of Mesh Networks
Full Mesh’s fiber usage is exponential with more nodes. This is the main reason why Mesh networks have been slow to scale.
However, with the significant increase in the concentration and density of communication networks, the moderate adoption of Mesh networks in trunk lines and dense urban areas has begun to be cost-effective.
The former bearer network mainstream equipment does not support automatic routing capabilities is also an important reason. Before SPN, SDH/PTN are using static path configuration service mode, such as SDH VC time slot cross-connect, PTN MPLS-TP, only support the configuration of the main two service paths, and after the configuration of the path is solidified.
This means that even if there are three or more physical routes in the topology, the service mode does not support automatic inversion to the third available route. When a failure occurs, the path can only be modified temporarily by manual intervention, but the service recovery time in this case is at least minute-level, exceeding the telecom-grade service protection requirement of allowing only 50ms of interruption.
With the SPN, the new generation of IPRAN Smart Network and other 5G bearer equipment supporting SR-TP/BE service automatic rerouting and commercial scale, the equipment capability has been able to fully utilize the advantages of MESH networking with more physical routes.
However, in the current specification of bearer network construction, the networking mode is still based on the port-shaped, hierarchical group ring network, which restricts the innovation and development of topology networking methods and approaches.
Therefore, it is strongly recommended that Mesh be included in the optional networking specifications of carrier groups. In localized scenarios, Mesh networks are promising, and in fact, some practices and applications have already shown promise.
Application Perspectives of Mesh-based Bearer Networks
For the scenarios that require mesh bearer network, we try to categorize and list some of them, and look forward to their value for network intelligence and 6G demand.
With the deepening of application practice, it is expected that new scenarios introducing the “ideal topology” will be continuously discovered, which will in turn promote the upgrading and development of bearer equipment and supporting cable room facilities, and will be of great benefit to the industry ecosystem.
Urgent Scenario 1: Geographically Challenged Local Bearer Networks
In some geographically harsh areas, fiber optic cables have sparse routes and long distances, and the areas they pass through are prone to earthquakes and floods. Even if there is no same route ring, the probability of simultaneous interruption of fiber optic cables or node power down in the ring is also very high.
If the third and fourth routes can be provided at this time, even with the help of neighboring counties fiber optic cable / OTN channel, can effectively protect network security, significantly reduce the risk of regional wide range of communication disruptions, the social value is very high.
Of course, the technical program does not pursue Full Mesh, combined with the actual fiber optic cable can provide as many routes as possible.
Application case of a western mountainous area in China with unfriendly geographic conditions for communication:
The red ring is the current convergence layer long ring, the distance is hundreds of kilometers long and nodes up to 10 or more, plateau, high-risk seismic areas and power supply difficulties, resulting in fiber-optic cable interruption and high risk of power outage in the server room.
The use of blue 1 optical path to provide the third intra-domain routing, but also the use of blue 2 + orange optical path, borrowed from neighboring counties to provide cross-domain 4th route, the final ring structure evolved into a day-type or eye-type structure, the ring itself and under the access layer survivability is greatly enhanced.
Urgent Scenario 2: Local Bearer Network Core Layer in Multi-core Server Rooms
The core layer of local SPN bearer network in some big cities, the number of core server rooms (3 and above), a large number of inter-room scheduling services, whether through the mouth type or ring, need to borrow a way around other no joints, at this time the MESH network can realize a jump directly to the advantage is very obvious.
Similarly, as SPN provincial backbone or urban backbone wavelength division, where a large number of services converge, the pursuit of the shortest path and the highest security, is also suitable for Mesh networking.
Usable Scenario 3: Local Bearer Network Aggregation Access Layer in Dense Urban Areas
Multiple SPN aggregation rings in dense urban areas are intertwined, and the short-ring security requirement in the network specification makes a single aggregation ring with weak convergence to the access layer, such as in accordance with the principle of proximity of the fiber optic cables, and many of the downlinked access rings are prone to cross the ring or even cross the IGP domains (the distributed control plane can not realize cross-domain re-routing).
In order to maintain the network specification, many access layer rings are prone to fiber optic cables around the far side, fiber core waste and the same route and other problems.
Therefore, it is recommended that the principle of dense urban convergence access layer networking can be considered “ring to network”, the same IGP domain to try to connect, in order to fully utilize the SPN re-routing escape protection capabilities.
Future Scenario 4: Satisfying The Need For Integrated Air, Space And Sea Communications In The 6G Vision
The evolution of communication network to intelligence has become the consensus of major carriers.
For the bearer network, bandwidth automatic on-demand allocation, routing optional, traffic engineering and even network simulation of these important self-intelligent network goals can not be reached without a complete physical topology as a base, if most of the services only 2 established physical path, these upper layer intelligent means may be just a setup, not much play value and space.
The 6G vision of air, sky, land and sea integrated communication needs, further challenges the existing ground network architecture.
Mesh network is theoretically not only the optimal goal of planar fully-connected networking, but also may require the development of three-dimensional Mesh-ized fully-connected networking in the future.
In fact, the use of UAV aerial base station disaster relief, SPN CPE as a fiber optic cable routing a single leased line access equipment utilizing 5G as a backup protection routing technology, has emerged.
Therefore, it is necessary to explore the method of ground mesh network construction as early as possible, and study and improve the technical capability of the equipment under various application scenarios.
In Brief
From the development of several generations of bearer networks, new technologies and new networks are almost inevitable, and the evolution of network topology to MESH network should be the trend.
The physical topology of the network tends to be “ideal”, the design work is greatly simplified, and it is easy to reach the security/bandwidth/delay optimization.
Network intelligence will have a solid foundation, topology above a variety of intelligent applications such as automatic routing, traffic engineering, network simulation, etc., will no longer be trapped in the underlying physical topology deficiencies.
For most of the general area with ring topology network, for the security needs of the business in use is enough. Full mesh network investment cost, fiber laying / room construction costs high cycle length, the initial use of non-full mesh may be more suitable. If you have any ideas, please feel free to contact us.