Internet Draft D. McDysan Document: draft-mcdysan-diffserv-ethernet- L. Yao 00.txt WorldCom Expires: January 2002 July 2001 Differentiated Services Over 802.3 Networks Framework Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [1]. Abstract This document describes the deliver of IETF Differentiated Services over MANs or WANs built from interconnected IEEE 802.3 MAC Bridges (switches). It describes the overlay model which uses Ethernet over MPLS to provide Diffserv support, and the mapping model which maps Diffserv PHBs to Ethernet user priorities and uses the inherent capabilities of relevant IEEE 802 technologies and, in particular, [802.1D-1998] queuing features and [802.1Q-1998] VLAN tags, to support Diffserv. 1. Introduction Gigabit Ethernet (GbE) and 10 Gigabit Ethernet (10 GbE) are emerging as important technologies for access to IP in the metropolitan and McDysan Expires January 2002 [Page 1] Internet Draft draft-mcdysan-diffserv-ethernet-00.txt July 2001 wide area networking arenas. As shown in Figure 1, metropolitan area networks (MANs) supporting Internet connectivity will use 802.3 Ethernet technology to backhaul traffic from customer sites to service providers' edge routers. +-----+ +----------+ +----------+ | CE1 |------| | | | +-----+ | +--------------------+ | | ESA | | | +-----+ | | +----------+ | PE | | CE2 |------+ +----+ | | | +-----+ | | | +----+ | +----------+ | ESB | | | +-----+ | | | | | CE3 |----------+ | +----------+ +-----+ | | +----------+ CE - Customer Edge Router ES - Ethernet Switch PE - Provider Edge Router Figure 1. Backhual Customer Traffic Using 802.3 Network This document describes the two models to support Diffserv over 802.3 Ethernet networks: the overlay model and the mapping model. Currently, little work is occurring in the IETF to support these models. This draft proposes that one or more IETF working groups add this to their charters. 2. Support Diffserv over 802.3 Networks To efficiently support Diffserv, 802.3 switches could have multiple queues and class-based scheduling mechanism on Ethernet interfaces. Traffic conditioning components, such as classifier, marker, policer and shaper, are also needed at the edge of 802.3 Ethernet networks to enforce access SLAs. 2.1 The Overlay Model This model assumes the support of Ethernet over an MPLS network. 802.3 frames are encapsulated into MPLS shim headers. Either E-LSP or L-LSP as defined in [MPLS-DIFFSERV] can be used to support Diffserv. When E-LSP is used, ingress 802.3 switches may mark each packet's EXP-bit based on the mapping between DSCP and EXP-bit, the input interface, or the input VLAN. 802.3 switches inside the MPLS network classify each packet solely based on its EXP-bit. One or multiple traffic classes denoted by different EXP-bit values are mapped into an output queue. The classified packets are en-queued accordingly. At ingress 802.3 switches, packets may be policed based on the pairs McDysan Expires January 2002 [Page 2] Internet Draft draft-mcdysan-diffserv-ethernet-00.txt July 2001 of LSP/EXP. At egress 802.3 switches, packets may also be shaped based on the pairs of LSP/EXP before transmission to edge routers. When L-LSP is used, ingress 802.3 switches may determine the attached label for each packet based on the mapping between the pairs of destination/DSCP and labels, the input interface, or the input VLAN. 802.3 switches inside the MPLS network classify each packet according to its label value. A traffic class may be denoted by one or multiple label values. One or multiple traffic classes are mapped into an output queue. The classified packets are en-queued accordingly. Packets may also be policed and/or shaped based on LSPs at ingress and/or egress 802.3 switches, respectively. 2.2 The Mapping Model This model utilizes the native Ethernet QoS as defined in [802.1D- 1998]. It requires that 802.3 switches map frames with different 802.1D user priorities into separate queues. There are a couple of reasons to use VLAN technology [802.1Q-1998] together with 802.1D user priority: - To allow IEEE 802.1D user priority information to be added to frames carried on IEEE 802.3 Ethernet MAC. - To allow frames of different customers to be classified and processed separately by using different VLAN tags. The user priority field in VLAN tag [8] is three bits in length and is therefore capable of representing eight priority levels, 0 through 7. Using the user priority field in the VLAN tag header, a single VLAN can support up to 8 classes of traffic. Ideally, separate queue for each pair of VLAN/user priority is desired to provide the finest granularity for buffer management. At customer edge routers, packets are classified according to their DSCP values. The customer edge routers then set the user priority fields in VLAN tags of the IEEE 802.3 frames carrying the packets according to the mapping between Diffserv PHBs and user priorities. For example, a possible mapping between Diffserv PHBs and Ethernet user priorities is given below: Diffserv Ethernet Ethernet PHB User Priority Traffic Class EF [RFC2598] 5 or 6 Voice or Video AFx [RFC2597] 4 Controlled Load CS 7 Network Control Default 0 Best Effort When transmitted between switches within the 802.3 Ethernet access network, IEEE 802.3 frames are classified and en-queued based on the pairs of VLAN/user priority. IEEE 802.3 frames may also be policed and/or shaped based on the pairs of VLAN/user priority at ingress and/or egress 802.3 switches, respectively. McDysan Expires January 2002 [Page 3] Internet Draft draft-mcdysan-diffserv-ethernet-00.txt July 2001 3. Security Considerations The use of Diffserv in 802.3 Ethernet networks leaves the possibility open for denial of service or theft of service attacks. However, this document introduces no new security issues on top of those discussed in the [DIFFSERV-ARCH]. 4. References [802.1D-1998] ôInformation technology-Telecommunications and information exchange between systems-local and metropolitan area networks-common specifications-Part 3: Media Access Control (MAC) Bridgesö, ISO/IEC 15802-3:1998, ANSI/IEEE 802.1D, 1998 [802.1Q-1998] ôIEEE Standards for Local and Metropolitan Area Networks: Virtual Bridged Local Area Networksö, IEEE 802.1Q, December 1998 [DIFFSERV-ARCH] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998 [RFC2597] J. Heinanen, F. Baker, W. Weiss, and J. Wroclawski, ôAssured Forwarding PHB Group ö, RFC 2597, June 1999 [RFC2598] V. Jacobson, K. Nichols, and K. Poduri, ôAn Expedited Forwarding PHB ö, RFC 2598, June 1999 [MPLS-DIFFSERV] F. Faucheur, and L. Wu, et al.," MPLS Support of Differentiated Services ", draft-ietf-mpls-diff-ext-09.txt, work in progress Author's Addresses David E. McDysan WorldCom 22001 Loudoun County Parkway Ashburn, VA Email: dave.mcdysan@wcom.com Lei Yao WorldCom 22001 Loudoun County Parkway Ashburn, VA 20147 Email: lei.yao@wcom.com McDysan Expires January 2002 [Page 4]