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Figure 91: S8700 /G700 /G350 Multi-Connect system (gateways deployed at remote
offices)
on page 348 illustrates a typical S8700 Multi-Connect system with G700 or G350
gateways deployed at two remote offices. It demonstrates a number of the features previously
discussed:
The network as designed is highly resilient. There are redundant routers and switches at
every level. In addition, the routers and Layer 3 switches are running VRRP to offer
redundant default gateways to endpoints.
The G700/G350s in the branch offices use LSPs for local survivability, should connectivity
to headquarters be disrupted.
The phones are powered by midspan power units connected to UPSs, reducing the
likelihood of power outages to the phones.
This network is very secure. Access-lists (set up in accordance with Appendix B) are
applied on the routers and Layer 3 switches. In addition, firewalls and intrusion detection
sensors have been deployed. The control networks are physically disconnected from the
building network, and only the C-LANs, MedPros, and S8700 administrative interfaces are
connected to the building network (through access-lists). This does provide sufficient
connectivity, however, for the G700/G350s to reach the C-LANs and the LSPs to reach the
S8700s.
DiffServ (L3) QoS has been applied on the T-1 circuits. In this case, 75% of the bandwidth
has been reserved for voice and voice signaling (DSCP 46) and 25% has been left for
everything else. Should voice traffic not fill the voice queue, the excess bandwidth is
passed to the data queue. This level of queuing may not be appropriate for all networks,
but is often a good place to start.
802.1Q has been enabled on the Ethernet segments. Voice and signaling traffic are both
tagged at 6, the value reserved for voice (and the second-highest level of Layer 2 QoS,
leaving the highest for network control). Because 802.1Q tags are stripped at every router
hop, they are regenerated at the far side of WAN links by mapping 802.1p tags based on
Layer 3 DiffServ tags.
Three network regions have been set up: one for headquarters and one for each branch
office. The codec sets have been established such that intra-region traffic uses G.711,
while inter-region traffic uses G.729.
Sample Multi-Connect deployment
Issue 3.4.1 June 2005
349
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