Internet Engineering Task Force B. Carpenter Differentiated Services Working Group IBM Internet Draft K. Nichols Expires in April, 2001 Packet Design draft-ietf-diffserv-pdb-bh-00 October, 2000 A Bulk Handling Per-Domain Behavior for Differentiated Services 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." This document is a product of the Diffserv working group. Comments on this draft should be directed to the Diffserv mailing list . The list of current Internet-Drafts can be accessed at www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at www.ietf.org/shadow.html. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract This document proposes a differentiated services per-domain behavior in which it is possible, in a properly functioning network, for traffic of this PDB to be "starved". This is in contrast to the Internet's "best-effort" or "normal Internet traffic" model. 1 Description of the Bulk Handling PDB This document proposes a differentiated services per-domain behavior [PDBDEF] called bulk handling (BH) which makes it possible to admit traffic of sufficiently low value (where "value" may be interpreted in any useful way by the network operator) that any other traffic should take precedence over this traffic in consumption of network link bandwidth. There may or may not be memory (buffer) resources allocated for this type of traffic. In some networks, there are types of traffic which are considered "optional"; that is, packets of these types ought to consume network resources only when no other traffic is present. This traffic type is considered to be distinct from "best-effort" traffic since the network makes no committment to delivering the packets while in the best-effort case, there is assumed to be an implied "good faith" committment that there are at least some network resources available for this traffic. This document proposes a bulk handling differentiated services per-domain behavior to implement this "optional" traffic service in a differentiated services domain. 2 Applicability A Bulk Handling (BH) PDB is for sending extremely non-critical traffic across a diffserv network. There should be the expectation that these packets may be delayed or dropped when any other traffic is present. Its use might assist a network operator in moving certain kinds of traffic or users to off-peak times. Alternatively, or in addition, packets can be designated for the BH PDB where the goal is to protect all other packet traffic from competition with the BH aggregate while not completely banning BH traffic from the network. A BH PDB should not be used for a customer's "normal internet" traffic nor for packets that ought to simply be dropped as unauthorized. The BH PDB would not be usefully depolyed in a network which is congested with non-BH traffic as this indicates no link resources to spare. 3 Rules 3.1 Edge rules There are no rules governing rate and bursts of packets beyond the limits imposed by the ingress link. The network edge must include a classifier that selects the appropriate BH target group of packets out of all arriving packets and steers them to a marker which sets the appropriate DSCP to select a PHB configured as described in the next section. No other traffic conditioning is required. 3.2 PHB configuration Either a Class Selector (CS) PHB [RFC2474], an Experimental/ Local Use (EXP/LU) PHB [RFC2474], or an Assured Forwarding (AF) PHB [RFC2597] may be used as the PHB for the BH traffic aggregate. This document does not specify the exact DSCP to use inside a domain, but instead specifies the necessary properties of the PHB selected by the DSCP. If a CS PHB is used, Class Selector 1 (DSCP=001000) is suggested. The PHB used by the BH aggregate inside a DS domain must be configured so that its behavior is that its packets are forwarded onto the node output link when the link would otherwise be idle. If the DS node uses a scheduler that is not capable of this strict starvation, an operator might choose to configure a very small link share for the BH aggregate and still acheive the desired goals. It is unlikely that a "fair sharing" scheduler would be configurable to yield the required PHB. If a CS PHB is used, note that this configuration will violate the "SHOULD" of section 4.2.2.2 of RFC 2474 [RFC2474] since CS1 will have a less timely forwarding than CS0. An operator's goal of providing a BH PDB provides a sufficient cause for violating the SHOULD. If an AF PHB is used, it must be configured and a DSCP assigned such that it does not violate the "MUST" of paragraph three of section 2 of RFC 2597 [RFC2597] which provides for a "minimum amount of forwarding resources". 4 Attributes of the BH PDB There are no quantifiable attributes of the PDB. The ingress and egress flow of the BH aggregate can be measured but there are no absolute or statistical metrics that arise from the PDB definition, though a particular network operator may configure the DS domain in such a way that a statistical metric can be associated with that DS domain. When the DS domain is known to be heavily congested with traffic of other PDBs, a network operator should expect to see no (or very few) packets of the BH PDB egress from the domain. When there is no other traffic present, the proportion of the BH aggregate that successfully crosses the domain should be limited only by the capacity of the network relative to the ingress BH traffic aggregate. 5 Parameters None required. 6 Assumptions A properly functioning network. 7 Example uses 1. For Netnews and other "bulk mail" of the Internet. 2. For "downgraded" traffic from some other PDB. 8 Experiences References [PDBDEF] "Definition of Differentiated Services Per-Domain Behaviors and Rules for their Specification", K. Nichols, B. Carpenter, draft-ietf-diffserv-pdb-def-01.txt [RFC2474] RFC 2474, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", K.Nichols, S. Blake, F. Baker, D. Black, www.ietf.org/rfc/rfc2474.txt [RFC2597] RFC 2597, "Assured Forwarding PHB Group", F. Baker, J. Heinanen, W. Weiss, J. Wroclawski, www.ietf.org/rfc/rfc2597.txt Authors' Addresses Brian Carpenter Kathleen Nichols IBM Packet Design, Inc. c/o ICAIR 66 Willow Place Suite 150 Menlo Park, CA 94025 1890 Maple Avenue USA Evanston, IL 60201 USA email: brian@icair.org email: nichols@packetdesign.com