August 2008
Intermediate to advanced
816 pages
22h 34m
English
book
The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition
by Rich Seifert, James Edwards
Content preview from The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
13.3. VLAN and Priority Tagging
In Chapter 11, "Virtual LANs: Applications and Concepts," and Chapter 12, "Virtual LANs: The IEEE Standard," I discussed the use of Virtual LAN (VLAN) tagging to explicitly indicate the VLAN association of a given frame. A VLAN tag contains both a VLAN identifier and a priority value indicating the user priority assigned to the frame. Through the use of tags, a device can signal user priority on LANs (such as Ethernet) that provide no native priority support. It is possible to perform this feat even if the device in question does not support VLANs. The special case of a tagged frame carrying a VLAN Identifier of all zeroes is not, strictly speaking, a VLAN tag. It is referred to as a priority tagged frame, and is depicted in Figure 13-6. VLAN identifier 0x000 is specifically reserved for this purpose.[]
[] While extensively discussed and permitted by the standard [IEEE98d], Priority tagging in this manner is not common. Because the complexity of implementing tagging for priority is not significantly less than that of implementing tagging for VLANs, most devices that insert tags do so in a VLAN context and use a non-zero value for the VLAN Identifier.
Figure 13.6. Priority-tagged Ethernet frame
While Figure 13-6 depicts a Priority-tagged Ethernet ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.