Design – Hierarchical
Where networks once were non-hierarchical (layer-1 design, layer-2 design, layer-3 design) they are generally now three-layer hierarchical in design (above). Cisco has been using this model for years and it gave a high-level overview of how a reliable network could be conceived but was largely conceptual because it did not provide specific guidance on “how-to” implement certain things, like:
- Implementing redundancy,
- Adding Internet Access,
- Accounting for remote users,
- Locating workgroup and enterprise services
Design – Enterprise Composite Network Model (ECNM)
Revisions to the hierarchical design showed redundant distribution and core devices and connections to make the hierarchical model more fault tolerant. The switch block design (above) explained how redundancy fit into a network, but still did not really adequately specify other parts of the network design. This lead to the Enterprise Composite Network Model (ECNM) development to address the failures of both the hierarchical model and switch block model.
This ECNM is broken into three large pieces:
- Enterprise Campus,
- Enterprise Edge,
- Service Provider Edge.
ECNM – Campus
The enterprise campus looks very much like the above switch block design with some added details:
- Campus Backbone (like the core layer of the hierarchical model),
- Building Distribution,
- Building Access,
- Management,
- Server Farm (Enterprise Services).
The ECNM Campus builds onto the Switch block design but gives specific guidance as to where to place servers and management equipment. Take note that the servers look like a switch block and are redundantly attached (dual-homed) to the switches (not really shown nicely in the diagram).
ECNM – Enterprise Edge
The Enterprise edge shows the connections that the enterprise has with the wide area (other networks) and include:
- E-Commerce,
- Remote Access,
- Internet Connectivity,
- WAN (Internal links to other branches).
ECNM – Service Provider Edge
The service provider edge includes the public networks that facilitate wide area (other networks) connectivity:
- Internet Service Provider (ISP),
- Public Switched Telephone Network (PSTN) for dialup,
- Frame Relay, ATM, and PPP for private connections.
Multiplexing
Historically voice traffic used one set of circuits and data traffic another. Also if you wanted more than one “number” the telecommunications company installed another physical line to your premises. If you wanted access to a data network they installed a data line for that purpose.
With line technologies like the T-carrier system (USA, Japan, Korea) 24 pulse-code modulated (I don’t know need to ask one the engineers about this), time-division multiplexed speech signals are carried over 2 copper pairs. This type of technology saved the telecommunications companies a lot of money in building out subscriber lines. The problem with T1 as a technology is that it cannot adjust as the customer usage requirements changes (see E-carrier system for Europe and other countries).
As technology changes so does the requirements from that technology; Modern networks are designed to carry voice, video, enterprise applications, normal LAN traffic and management traffic all on the same single secure infrastructure (convergence). The traffic is forced (statistically multiplexed) to share access to the network.
Service-Orientated Network Architecture (SONA) and Intelligent Information Network (IIN)
As covered above “Multiplexing” described the idea of a converged network as a system that integrates what was previously disparate systems (voice, video, data). The traffic types usually found on a converged network would include, but may not be limited to:
- voice signalling and bearer traffic,
- Core application traffic (ERP and CRM),
- Transactional traffic related to database interactions (SQL),
- Network management traffic for monitoring and maintaining the network structure (including routing protocol traffic),
- Multicast multimedia,
- Other traffic (web, e-mail, file transfer).
Each of the above traffic types has its own requirements and expectations that govern its successful execution. These requirements include security, QoS, transmission capacity, and delay.
To support this kind of multiplexed traffic, Cisco routers are able to implement filtering, compression, prioritization, and policing (dedicating network capacity). Except for the filtering process these processes are collectively known as QoS.
As an alternative to QoS, Cisco has an ideal called the Intelligent Information Network (IIN). This vision describes a network that integrates network and application functionality cooperatively allowing the network to be “smart” about how it handles traffic to minimize the footprint of applications. The IIN evolution is described in three phases:
- Phase 1: Integrated Transport, deals with a converged network, built along a similar fashion of the ECNM and based on open standards (cross-compatibility)
- Phase 2: Integrated Services, posits virtualization of resources such as servers, storage and network access; to move to an “on-demand” model. Don’t think marketing/advertising “virtualization” think practical virtualization the ISR routers (routing, switching, voice, network management, security and wireless) designed as an aio (all-in-one) appliance and Vitalizing Servers (if you have proper designed for the job servers) you can’t be trying this on SMB servers or try recycling 10 year old technology and thinking “bargain let’s load 5 operating systems on this”.
- Phase 3: Integrated Applications, using application orientated networking (AON) to make the network “aware” allowing the network to actively monitor and participate in service delivery.
Service-Orientated Network Architecture (SONA) is the practical application or “how-to” of IIN in enterprise networks. SONA breaks down IIN into three layers;
- SONA Infrastructure Layer is basically the same as IIN Phase 1,
- SONA interactive Services Layer maps to IIN Phase 2,
- SONA Application Layer has the same concepts as IIN Phase 3.
Resources:
Aragoen Celtdra on BSCI: Network Architecture and Design
Notes and Notices:
This is a part of my personal BSCI notes and research to assist myself in learning and understanding the concepts and theory for the BSCI exam. I learn by making notes reading and writing things down and wish to file them where I can’t lose them. These notes are not to be seen, judged or mistaken for replacements to Cisco recognized and authorized training which I personally support and attend and suggest you undertake if you are going for the BSCI Certification.
