Home > Networking Tips > > VoIP campus VLAN design
Networking Tips:
EMAIL THIS
 TIPS & NEWSLETTERS TOPICS 


VoIP campus VLAN design


Rich Parsons
10.07.2004
Rating: -3.94- (out of 5)


Digg This!    StumbleUpon Toolbar StumbleUpon    Bookmark with Delicious Del.icio.us   


A company's campus network typically is made up of at least two "hierarchical layers" of LAN switching devices. Within these layers, Virtual Local Area Networks (VLANs) are used to manage traffic queues.

A VLAN is used for logically segmented traffic or a broadcast domain over a switched network. For example, all workstations and servers used by a particular division within an organization can operate over the same VLAN, regardless of their physical locations or connections within the campus. VLANs meet the scalability, security, and management requirements of a network infrastructure.

Today's access switches are required to support IP telephony alongside data traffic in the LAN. The switches also are able to support multiple VLANs on the access port connected to an IP phone. However, the introduction of IP phones into a data switched campus presents some challenges. The current IP addressing scheme could be saturated with IP addresses for data endpoint, thus limiting the IP address space available for IP phones. In addition, the combination of voice and data traffic over the same VLAN could reduce the necessary quality for VoIP traffic, especially in the event of broadcast storms.

These challenges can be addressed by creating a separate VLAN and isolating the voice traffic onto this VLAN. The switch port would have an auxiliary VLAN carrying voice traffic to and from the IP phone, and the port would have data traffic traversing the native VLAN carrying data traffic to and from the PC or data endpoint. The isolation of the voice traffic onto an auxiliary VLAN also permits a large quantity of phones to be implemented into the network infrastructure by essentially creating a new subnet and a new set of IP addresses.

As mentioned previously, voice and data on the same broadcast domain can deteriorate sound quality. When the transmission of data pack...


Digg This!    StumbleUpon Toolbar StumbleUpon    Bookmark with Delicious Del.icio.us   



RELATED CONTENT
Voice/data Convergence
Networking Products of the Year 2004
The best of 2004
Elements of VoIP QoS
Telephony 'just another IP application' according to FCC
A significant VoIP benefit - Unified messaging
IP telephony development tools
SPIT, or Spam over Internet Telephony
First Wi-Fi handset makes its debut
Duties of an IP telephony gateway when integrating VoIP and the PSTN
VoIP and NAT

RELATED RESOURCES
2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems
Search Bitpipe.com for the latest white papers and business webcasts
Whatis.com, the online computer dictionary


ets become bursty, the inherent delay and jitter within the network adversely affects voice quality. However, the separation of voice traffic on an auxiliary VLAN increases its quality. For example, Cisco switches utilize Class of Service parameters to prioritize voice traffic based on 802.1Q VLAN tagging. Once voice traffic is prioritized, it can be then expedited using a higher priority queue. In addition, the switch can be used to trust or adjust the 802.1Q priority naturally assigned by the phone.

Separate VLANs over a converged infrastructure also augment the security of the network. Cisco's CallManager can be configured to deny the forwarding of auxiliary voice packets to the PC. Conversely, the PC is able to use VLAN tagging without needing permission into the voice VLAN.

Finally, the implementation of an auxiliary/native VLAN solution eases the day-to-day operation or troubleshooting of the converged infrastructure. Due to the auxiliary voice VLAN and its IP address range's segmentation from the data infrastructure, the identification of problematic source components is greatly enhanced. Access-lists are additionally easier to design and configure when separate VLANs exist.

While it is not mandated to implement auxiliary and native VLANs for a converged design over a campus environment, the above mentioned benefits appear to warrant its recommendation.


Richard Parsons (CCIE#5719) is a Manager of Professional Services for Callisma Inc., a wholly owned subsidiary of SBC. He has built a solid foundation in networking concepts, advanced troubleshooting, and monitoring in areas such as optical, ATM, VoIP, routed, routing, and storage infrastructures. Rich resides in Atlanta GA, and is a graduate of Clemson University. His background includes senior and principal consulting positions at International Network Services, Lucent, and Callisma.


Rate this Tip
To rate tips, you must be a member of SearchNetworking.com.
Register now to start rating these tips. Log in if you are already a member.


Submit a Tip




DISCLAIMER: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.



Networking Solutions for Business

Alcatel-Lucent Network Business Communications Solutions

About Us  |  Contact Us  |  For Advertisers  |  For Business Partners  |  Site Index  |  RSS
SEARCH 
TechTarget provides technology professionals with the information they need to perform their jobs - from developing strategy, to making cost-effective purchase decisions and managing their organizations' technology projects - with its network of technology-specific websites, events and online magazines.

TechTarget Corporate Web Site  |  Media Kits  |  Site Map




All Rights Reserved, Copyright 2000 - 2009, TechTarget | Read our Privacy Policy
  TechTarget - The IT Media ROI Experts