RE: stds-80220-requirements: 802.1q/p
David,
Just wanted to reiterate and further clarify the reasoning behind the proposed deletion of "4.5.2 802.1Q/P tagging".
The essence of the argument why not to mandate 8021Q/P is that we have decided a while ago to keep 802.20 network architecture agnostic. One of the reasons for that decision was to speed up standard development while broadening the applicability of the standard to multiple environments, existing and emerging.
The IEEE 802.1Q standard defines the operation of VLAN Bridges that permit the definition, operation and administration of Virtual LAN topologies within a Bridged LAN infrastructure. The IEEE's 802.1Q standard was developed to address the problem of how to break large networks into smaller parts so broadcast and multicast traffic would not grab more bandwidth than necessary.
The reasoning you gave below to why 802.1q/p should be required for 802.20 is "Tagging will support the L2 switching such that network egress traffic can be switched by a L2 device to the appropriate L2 termination device for managing backbone traffic or distinguishing traffic for wholesale partners in a wholesale environment." The way the network agnostic argument applies here is that for example in a traditional access network (e.g. DSL or 3GPP2) a PPP session (associated with the Network Access Identifier - NAI, which is exchanged in the LCP PPP phase) would be used to switch network egress traffic at the Network Access Server (NAS) to the appropriate L2 termination device for managing backbone traffic or distinguishing traffic for wholesale partners in a wholesale environment. If we were to require 802.1q/p or use it as an evaluation criteria in 802.20, solutions supporting the more common PPP access networks would be prohibited or unnecessarily disadvantaged, thus limit!
ing the scope of 802.20. Given the multitude of infrastructure equipment that support the PPP based network access paradigm (e.g. NAS, AAA, etc), that would unnecessarily prevent 802.20 from also being deployable in readily available and economically viable PPP network access architectures.
Similarly, 802.1p and its 8 level of priority mimics IP precedence level and is extraneous in light of the DiffServ requirements we adopted.
Hope that this will now lay this issue finally to rest as agreed a long time ago and allow us to focus our energy on the remaining open items.
Best regards,
Branislav
-----Original Message-----
From: owner-stds-80220-requirements@majordomo.ieee.org [mailto:owner-stds-80220-requirements@majordomo.ieee.org]On Behalf Of Mcginniss, Dave S [GMG]
Sent: Monday, November 17, 2003 8:08 AM
To: stds-80220-requirements@ieee.org
Subject: stds-80220-requirements: 802.1q/p
4.5.2 802.1Q/P tagging (open)
Editors Note: This section is proposed for deletion because this is tied a specific network architecture.
Current text
[802.1Q tagging must be supported by the system (such that network egress traffic can be switched by a L2 device to the appropriate L2 termination device for managing backbone traffic or distinguishing traffic for wholesale partners in a wholesale environment).]
Proposed Text
802.1q tagging should be supported by the 802.20 system or some other mechanism (i.e. policy routing). Tagging will support the L2 switching such that network egress traffic can be switched by a L2 device to the appropriate L2 termination device for managing backbone traffic or distinguishing traffic for wholesale partners in a wholesale environment. Tagging can also be used to facilitate a retail captive portal service model. By tagging traffic from a mobile terminal that is unknown (i.e. mobile terminal is un-provisioned) it can be switched at L2 to a system enabling a self provisioning system model. By tagging control and management traffic it to can be switched and separated as close to the base station as possible. All of these can be accomplished at a higher layer but are simpler to implement if 802.1Q tagging is supported.
802.1p
The 802.1Q standard specifies that tags be appended to a MAC frame. The VLAN tag carries VLAN information. The VLAN tag has two parts: The VLAN ID (12-bit) and Prioritization (3-bit). The 802.1P implementation defines the prioritization field. 802.1p defines a 32-bit tag header that is inserted after a frame's normal destination and source address header info. Switches, routers, servers, desktop systems, mobile terminals, or base stations can set these priority bits. Switches and routers can prioritize traffic based on these tags.
Rational
By driving these functions to layer 2 a provider can build a flatter network supporting simple IP handoff over a larger 802.20 coverage area. These functions can be supported in other ways at a higher layer but are most efficiently handled at layer 2. The evaluation criteria group should report support for tagging so that the 802.20 group can factor support in the selection process.
David S. McGinniss
Sprint Broadband Wireless Group
Principal Engineer II
(630) 926-3184
david.s.mcginniss@mail.sprint.com