PUTTING IT ALL TOGETHER: SAMPLE NETWORKS

The following diagrams illustrate notional networks supporting various levels of Citrix activity. Due to size constraints, none of the diagrams are intended to be complete in every detail or completely accurate in depicting physical connectivity. Chapter 17 will delve into greater detail regarding each aspect of a sample network. When documenting your network design (a necessity), three major documents are needed: First, a physical diagram similar to those that follow. Second, a logical diagram to document the relationship between Layer 2 boundaries (VLANs) and Layer 3 boundaries (routed networks) for each protocol (TCP/IP, IPX/SPX, and so on) you must support. Finally, a documented naming and addressing scheme, to address both protocol address and naming convention (NetBIOS Name, DNS Host Name ), is essential.

As examples, three business scopes (small businesses, medium- sized businesses, and large businesses) are addressed. Additionally, the medium-sized business shows two possible scenarios, branches connected via private WAN media and an Internet-centric and VPN approach.

The Small Business Network

The small business model (see Figure 6-20) uses the same basic equipment as larger scale deployments, but separation between hierarchical layers is limited. The local distribution, core, and server access layer are collapsed and exist on the same Layer 3 switch. Multiple protocols are isolated by separate Layer 2 VLANs connected to the Layer 3 core ; this concept is implied , but not illustrated , in subsequent diagrams.

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Figure 6-20: A small business network example

The Medium-Sized Business Network

The medium-sized business network shares component parts with its small business counterpart , but employs more specialized distribution and core layer hardware to isolate local users, DMZ networks, and branch offices from the production server environment in the core.

Figure 6-21 depicts a typical mid-sized business with large branch offices connected via dedicated media. The distribution layer switch serves to aggregate traffic from LAN, WAN, and Internet sources, and to insulate the core switch and server farm from this traffic.

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Figure 6-21: A medium-sized business network example (dedicated media)

Figure 6-22 depicts a model more suited to a medium-sized business with many small branches (such as point of sale [POS] sites) where dedicated WAN media are cost-prohibitive. A combination of Internet access to the Web Interface site, VPN access, and secure access via Citrix Access Gateway provides a flexible, secure WAN without dedicated links. In both cases, branch-to-Internet or LAN user -to-Internet traffic flows never traverse the core and are kept in check by the Packeteer (to protect Internet-based users and VPN traffic).

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Figure 6-22: A medium-sized business network example (Internet/VPN media)

Again, like the small business model, the "server-specific" access and distribution layers are collapsed onto the core switch (see Figure 6-23). Redundant connectivity is added between the core and the distribution layer switch for reliability and survivability . All aspects of the local server farm, particularly the Presentation Server farm, are more robust and more redundant.

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Figure 6-23: A medium-sized business network example (Core)

The Large Business Network

The large business model (the beginnings of a true enterprise model) moves away from a collapsed structure to a hierarchical network design where each layer is purpose-built. Layer 2 connectivity becomes far less prevalent , with redundant Layer 3 links being the norm.

Figure 6-24 illustrates the more robust access layer structure expected in a large business model. Note the redundant Internet, multiple VPN methods , and access aggregation for specific groups of services (WAN aggregation router).

image from book
Figure 6-24: A large business network example (distribution/core layer)

Typical large business distribution and core components are shown in Figure 6-25. Virtually every aspect of the distribution and core layers are redundant and "self-healing" by either Layer 3 route convergence or Layer 2 (STP) convergence. For additional resilience, the Presentation Server farm itself has been split into two physical zones. Both physical zones still function as a single logical load-balanced farm, even on different subnets. The implication is that if an organization requires on-campus survivability and has adequate (gigabit) connectivity, it can distribute the farm across multiple buildings with no loss of functionality.

image from book
Figure 6-25: Large business distribution and core components


Citrix Access Suite 4 for Windows Server 2003. The Official Guide
Citrix Access Suite 4 for Windows Server 2003: The Official Guide, Third Edition
ISBN: 0072262893
EAN: 2147483647
Year: 2004
Pages: 137

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