Search /
Docfinder:
Advanced search  |  Help  |  Site map
RESEARCH CENTERS
SITE RESOURCES
Click for Layer 8! No, really, click NOW!
Networking for Small Business
TODAY'S NEWS
iPhone 5 rumor rollup for the week ending Feb. 10
Forget Public Cloud or Private Cloud, It's All About Hyper-Hybrid
Apple passes HP as largest tech company
How to get the IRS' attention: Forge nearly $8 million in tax returns, steal identities
Much of Western U.S. is a 3G wasteland, says FCC
How the Phoenix Suns basketball team takes on social media attacks
Microsoft details Windows 8 for ARM devices
Resume Makeover: How an Information Security Professional Can Target CSO Jobs
Blogger exposes major Google Wallet security flaw
Web app lets enterprise set security, sharing for Google Apps users
Cloudscaling to offer OpenStack private cloud platform
Macs take on the enterprise
Valentine's Day Patch Tuesday: Microsoft to issue 9 patches, 4 critical
Mobile World Congress sneak peek: Quad-core smartphones, Ice Cream Sandwich & more
/

QoS at the IP layer, Part 2

Related linksToday's breaking news
Send to a friendFeedback

Sign up to receive this and other networking newsletters in your inbox.

Last time, we introduced the type-of-service byte as a way IP can support quality of service. Because ToS has limitations, especially when multiple networks are involved, the IETF has created another QoS mechanism called Differentiated Services, or DiffServ. DiffServ, which offers up to 64 service classes, reinterprets the values offered in the ToS byte.

The DiffServ model was developed to differentiate IP traffic so that the traffic's relative priority could be determined on a per-hop basis. By using DiffServ, traffic is classified based on priority. Then the traffic is forwarded using one of three IETF-defined per-hop behavior (PHB) mechanisms. This approach allows traffic with similar service characteristics to be passed with similar traffic guarantees across multiple networks, even if the multiple networks don't provide the same service the same way. This is an important feature because, as our readers know, the Internet is really a network of multiple service provider networks.

DiffServ replaces the first bits in the ToS byte with a differentiated services code point (DSCP). The DSCP is then mapped to the PHB. This technique allows service providers to control how the DSCP codepoints are mapped to PHBs, and each time a packet enters a network domain it may be re-marked.

DiffServ, as described in RFC 2475, allows for five categories of service differentiation. They are: Relative Priority Marking; Service Marking; Label Switching; Integrated Services/Resource Reservation Protocol; and Static per-hop Classification.

We'll continue our discussion of DiffServ and PHBs next week.

RELATED LINKS

Steve Taylor is President of Distributed Networking Associates and Publisher/Editor-in-Chief of Webtorials.Com. For more detailed information on most of the topics discussed in this newsletter, connect to Webtorials.Com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP.

Larry Hettick is an independent consultant, with 19 years of experience in telecommunications and data communications marketing and product management for service providers and equipment vendors. He can be reached at larry@larryhettick.com

You can reach the authors at taylor@webtorials.com or larry@larryhettick.com.

Convergence archive
Past newsletters.

DiffServ working group
IETF.org

RFC 2475 - An Architecture for Differentiated Services
IETF.org


NWFusion offers more than 40 FREE technology-specific email newsletters in key network technology areas such as NSM, VPNs, Convergence, Security and more.
Click here to sign up!
New Event - WANs: Optimizing Your Network Now.
Hear from the experts about the innovations that are already starting to shake up the WAN world. Free Network World Technology Tour and Expo in Dallas, San Francisco, Washington DC, and New York.
Attend FREE
Your FREE Network World subscription will also include breaking news and information on wireless, storage, infrastructure, carriers and SPs, enterprise applications, videoconferencing, plus product reviews, technology insiders, management surveys and technology updates - GET IT NOW.