CSIS 430 Advanced Networking : Synchronous Optical Networking

lows excess padding for the data which is multiplexed to progress within the overall framing; here the data is clocked at a varied rate compared to the frame rate (SONET/SDH 2017). The protocol made can be more complicated by the allowance of this padding; however, enhanced all-around performance can be gained at the end.

SONET standard was deployed in North America and is termed as the North American Standards. Synchronous Transport Signal (STS) is not only carried out through the fibre optic line, but also the signal is carried out electronically through the coaxial cable line. From the hierarchy of the SONET, it can be noted that the STS-1 operates at the OC-1 level at 51.84 Mbps and it has the capacity of 28 DS1s. It can be also noted that STS-3 operates at the OC-3 level at 155.52 Mbps and it has the capacity of 84 DS1s (5 Wan Technologies 2017). From the SONET hierarchy, it can also be found that the STS-12 operates at OC-12 at 622.08 Mbps and it has the capacity of 336 DS1s. STS-1 is at the base level, if three such STS-1s are multiplexed, one channelized STS-3 can be formed. If three unchannelised STS-1s are multiplexed, then it is known as the unchannelised STS-3c or STS-3concatenated. Four STS-3s if multiplexed, one STS-12 can be formed.

DPT uses the SONET framing and implies intelligent protection switching in the case of any failures related to nodes. DPT utilises the counter-rotating ring structure for the metro applications (Doherty, Anderson and Della 2008). DPT also utilises the ring structure with a central switching device for service PoP backbones and thus it facilitates the SONET networks.

Figure 1: SONET and SDH Standards

(Source: 5 Wan Technologies 2017)

Sdh

Synchronous Digital Hierarchy (SDH) is the standard which gets deployed later after the SONET. It first gets deployed in the Europe and then gets deployed in the rest of the world. SDH Hierarchy works similar to the SONET Hierarchy and is followed in the rest of the world. The SONET uses the STS signal whereas the SDM uses the Synchronous Transport Module (STM) frame format. This STM signal is followed in the rest of the world. In case of SONET, the signal STS-3 signal operates at the OC-3 level at 155.52 Mbps and its capacity is 84 DS1s. The STM-1 works similar to STS-3 of SONET (5 Wan Technologies 2017). It operates at the level of OC-3 at 155.52 Mbps and it has the capacity of 63 E1s. An STM-1 operates at 155 Mbps. If four such STM-1s are multiplexed, then one STM-4 can be built. The STM-4 signal operates at the OC-12 level at 622.08 Mbps and it has the capacity of 252 E1s. Again, the STM-16 signal operates at the OC-48 level at 2488.32 Mbps it has the capacity of 1008 E1s. The STM-64 operates at the level OC-192 at 9953.28 Mbps and it has the capacity of 4032 E1s. The STM frame is continuous in nature and gets transmitted in a serial way that is row-by-row and byte-by-byte.

The transport overhead is utilised to measure the signal transmission error rate. The transport overhead consists of the following- section overhead- it is called RSOH and it contains the 27 octets about the frame structure, line overhead- it is called MSOH and it contains the 45 octets about the auto protection switching messages, AU pointer- addresses the location of J1 byte in the payload (SONET/SDH 2017). The path virtual envelope consists of Payload overhead (POH) and Payload. The POH consists nine octets for measuring the signal errors.

ATM Technology

ATM is basically the virtual circuit switching techniques. The ATM technology is the deterministic networking system responsible to cater the quality of service.  The ATM technology caters high level of control from end to end. The technical aspects which ATM contains caters are -Scalable performance- The data can be sent in an agile fashion and in an accurate manner via ATM. The ATM works on high-speed media as well as on the low-speed media. Quality of Service- ATM facilitates both speed and accuracy of data transfer What Is (ATM? Asynchronous Transfer Mode (ATM) 2017). Integration of various traffic updates- ATM provides the facility to assimilate the varied data service, voice and video on a single network. ATM.

ATM Network allows transfer of varied cells through a definite path known as a varied channel (VC). A full duplex communication can be set up with the help of ATM. The LANs have the capability to detect the missing information and the corrupted information. The cells get transmitted in specific orders. The Virtual Path Identifier is utilised by the ATM Network in the ATM header to transfer data frames. A switch reads the ATM header; the switching table gets compared to the switch and thus the latency gets reduced and the correct output is acquired (ATM? Asynchronous Transfer Mode (ATM) 2017). The ATM header contains all the required information and the information is always available in ATM header. Thus the tasks can be implemented in hardware simply by diminishing latency. ATM has the capability to handle the requirements of isochronous traffic like the video data and the voice data. ATM can handle the non-isochronous traffic like the LAN data.

The virtual connectors (VC) are used to connect the dedicated servers. The service provider connects with the dedicated server through this virtual circuit, the service providers can learn the dedicated server’s address and the data flow. When a new network connection is required, the virtual circuit connects them to the same physical network line and not through a separate line (5 Wan Technologies 2017). ATM is the cell-switching technology that allows the fast building of switches. The ATM allows the transition of video, voice and data on the same network. The ATM allows the customers to share network resources with the service provider and also allows the customers to creating private VPNs.

ATM networks are composed of ATM endpoints as well as ATM switches. The ATM switches are responsible for transferring data stream via the ATM network (Doherty, Anderson and Della 2008). ATM endpoints include the routers, data service units’ workstations, video codecs and LAN switches.

MPLS Technology

The full form of MPLS technology is the Multi-Protocol Label Switching, it provides the combination of a high-performance forwarding mechanism, OAM functions, data path protection and the mapping onto various technologies and connection establishment (MPLS Part 1: The Basics of Label Switching 2017). It lies within the Layer 2 and Layer 3 network thus it is popularly known as Layer 2.5 network.

MPLS provides the privacy as well as the security of Frame Relay or ATM Network. The MPLS enables any-to-any connectivity and also provides the flexibility of an IP-based network. The MPLS resides in between the Layer 2 and Layer 3 protocol. The encapsulation is basically the packet switching technique procedure and the encapsulation technique procedure and this technique are adapted to route data over the WAN connection. The MPLS data can be used over any layer 2 technology, which involves both the PPP and the Ethernet. MPLS uses the Label-Switched Path (LSP) to connect each location and thus connected on to the providers’ network. LSP works almost similar to Frame Relay virtual circuit, it is not dependent on Layer 2 technology. LSP works in unidirectional motion and the customers require matching LSP (5 Wan Technologies 2017). The routers that are involved with the running of MPLS protocol are called Label Switching Router (LSR), the MPLS domains also have three associate domains, one is the Label Edge Router (LER) or the LER is a special type of LSR. When the customers’ data arrive in the MPLS domain the LER looks for the header. The LER assigns labels and they are based on definite QoS requirements, the destination IP network, source and destination IP network, destination IP network and the application type.

The MPLS is developed to speed up the routing of packets through the WAN network. MPLS has multiple benefits to offer, it is developed to accelerate the routing of packets via WAN network. MPLS has facilitated the service providers to the enterprise customers which includes the VPNs, Layer 2 tunnelling, multiprotocol support and QoS. The MPLS architecture is divided into two planes or two layers- one is the Control plane as well as the Data plane (Doherty, Anderson and Della 2008). The Control plane exchanges the routing information between the adjacent devices. The forwarding information is handled by the Data plane. ATM or Frame is more secured compared to MPLS. The MPLS is not encrypted by default, however, it can be encrypted if required.

References

5 Wan Technologies 2017. 5 WAN TECHNOLOGIES. [online] Available at: https://www.youtube.com/watch?v=BAvQY9_cvp4 [Accessed 22 Nov. 2017].

Doherty, J., Anderson, N. and Della Maggiora, P.L., 2008. Cisco networking simplified. Cisco Press.

MPLS Part 1: The Basics of Label Switching 2017. MPLS Part 1: The Basics of Label Switching. [online] Available at: https://www.youtube.com/watch?v=U1w-b9GIt0k [Accessed 22 Nov. 2017].

SONET/SDH 2017. [online] Available at: https://www.fiberoptic.com/adt_sonet_sdh.htm [Accessed 22 Nov. 2017].

What Is ATM? Asynchronous Transfer Mode (ATM) 2017. What Is ATM? Asynchronous Transfer Mode(ATM). [online] Available at: https://technet.microsoft.com/en-us/library/cc783455(v=ws.10).aspx [Accessed 22 Nov. 2017].