Talk:IEEE 802.1Q

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User:Pligwash:umm that only adds up to two bytes. are the remaining two used for the original ethertype?

sort of... the 802.1q tag is added between the source address and type fields of the ethernet frame. It consists of 0x8100 (protocol identifier for 802.1q tagged packet, 2 bytes), priority (3 bits), CFI (1 bit) and VLAN ID (12 bits), total four bytes. So the existing ethertype field is simply "moved up" by 4 bytes. Hope this makes sense... --Ali@gwc.org.uk 20:41, 15 November 2005 (UTC)[reply]

I think it's more like the VLAN tag goes right after the ethernet frame, the ethernet type is set to the 0x8100, and the VLAN tag has the encapsulated protocol in it (ie, the 0x0800 for IP or whatever). I think this makes more sense because if you are building a packet from scratch, there is nothing to insert between anything, you just add the ethernet header, vlan header, and then higher-level protocol(s). Greearb (talk) 17:40, 9 September 2008 (UTC)[reply]

Case of 'Q'

Note that the 'Q' is supposed to be upper case; see the IEEE web site: http://www.ieee802.org/1/pages/802.1Q.html. Although lower case is commonly used, it is technically incorrect. --Rick Sidwell 06:33, 17 December 2005 (UTC)[reply]

Native and Management VLAN

The Native VLAN and the Management VLAN are not the same. In fact, they should be different in a well-designed LAN. Pgallert (talk) 16:12, 29 April 2008 (UTC)[reply]

Oh yes, and while the notion of a "Native VLAN" is an important part of the 802.1Q standard, the idea of "Management VLAN" is not. This rather refers to network design. I gonna be bold. Pgallert (talk) 16:31, 29 April 2008 (UTC)[reply]

Update of figure two

The text related to figure two states: "...in such cases, an alternate TPID such as hex 9100, or even 9200 or 9300, sometimes may be used for the outer tag; however this is being deprecated by 802.1ad, which specifies 88a8 for service-provider outer tags."

Shouldn't the figure TPID field then be changed to 88a8 since that is what is being usedm not 9100? —Preceding unsigned comment added by 77.110.39.122 (talk) 09:50, 26 November 2008 (UTC)[reply]

Overall Frame Length - 1500

There is an error in the diagrams. The overall frame length should be bounded by the standard sizes of 64bytes - 1518 bytes. This should be the case regardless of the number of VLAN tags added.

Thus, the diagrams should read n=42-1496 for the single tagged frames, and n=38-1492 for the double tagged frame. —Preceding unsigned comment added by Neilneil2000 (talk • contribs) 11:37, 17 August 2009 (UTC)[reply]

Not so. .1q extends the maximum frame size so that tagged frames can still have a payload of 1500 bytes. --Stefan Bethke (talk) 10:00, 25 July 2010 (UTC)[reply]

66-bit Addressing

Some amendmens have been made that add an explanation of using tagged frames for extended addressing. The relevant changes are:

VLAN Identifier (VID) is extended to read: The 12-bit field can be partitioned into two 6-bit fields to extend the Destination and Source 48-bit addressing. With Triple-tagging 18 bits are added to the 48 resulting in 66 bits of addressing.
Triple-tagging is extended: The 12-bit VID fields extend the 48-bit Destination and Source addressing to 66 bits. The middle 3-bit PCP field could be used as a Virtual TTL or Hop-Count to ensure packets do not circulate forever. A more complex ingress-egress encoding overloads one of the bits. The last 3-bit PCP field is used for Content Rating - 000 NR to 111 XXX. The three CFI bits are combined to encode the Next Header (or Protocol) found in the Payload Section. Only two of the CFI bits can be used, resulting in four protocols. [NOP,ICMP,UDP,ENCAP] The NOP (No Protocol) is a tiny Payload Section mostly for IP byte/pipe streams. ICMP provides control. UDP adds Ports, a semi-redundant length and an optional Checksum from IP. The ENCAP protocol or Payload Type allows all of the above to be ENCAPsulated without the Preamble but including CRC/FCS. With ENCAP the tags, TTL and length are placed in front of the 48-bit address fields to allow hardware to process those bits first, reducing latency.

There is no basis in IEEE or other standards, vendor implementations or elsewhere. If you have references describing frames extended in such a way, please feel free to add the explanations back with those references. I have reverted those changes again. —Preceding unsigned comment added by Stefan Bethke (talk • contribs) 10:07, 25 July 2010 (UTC)[reply]

This 66-bit addressing topic is mentioned in one paragraph in the article. If it is notable, it needs to be properly introduced. If it is not notable, we should, of course, remove it. --Kvng (talk) 15:41, 28 September 2010 (UTC)[reply]

History

This article needs a history section. The standards documents themselves do not give a revision history. --Kvng (talk) 02:11, 31 August 2010 (UTC)[reply]

Probably citation of wrong standard

[...]but the current (IEEE Std 802.1D- 2004) standard does not use the terms trunk or native.[...] -> I'm not quite sure, but 802.1D is "Rapid Spanning Tree Protocol" so shouldn't we instead refer to 802.1Q here? 217.91.83.80 (talk) 12:35, 27 January 2011 (UTC)[reply]

native VLAN

The write up of native VLAN uses VLAN 2,3,4 and the words "with VLAN 2 being the Native VLAN". I read elsewhere that that the native VLAN has vlan id = 1. Can a knowledgeable person confirm and correct the page if necessary please? — Preceding unsigned comment added by 87.113.81.77 (talk) 17:32, 4 November 2011 (UTC) ..,..[reply]