draft-ietf-issll-rsvp-cap-01.txt Internet Draft Syed, Hamid, draft-ietf-issll-rsvp-cap-01.txt Nortel Networks November, 2000 Capability Negotiation: The RSVP CAP Object 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. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. 1. Abstract The DCLASS object is proposed in [DCLASS] to represent and carry Differentiated Services Code Points (DSCPs) within RSVP messages. The principle use of the DCLASS object is to carry DSCP information between a DS network and upstream nodes that may wish to mark packets with DSCP values. A network element in the DS network determines the value for DSCP which is further carried as a DCLASS object in RSVP RESV message to the sender host. There may be situations where the sender host is not capable or may not wish to mark the packets. Currently, there is no way for the host or network devices to specify their capabilities to the downstream nodes. This draft proposes a capability object (CAP object) in the RSVP PATH message that can be used to convey end host/upstream node capabilities to the downstream network. It also defines one bit in the CAP field of the CAP object to convey the host/upstream node's Hamid Expires May, 2001 [Page 1] draft-ietf-issll-rsvp-cap-01.txt November, 2000 marking capability/willingness for accepting a DCLASS object from the downstream network and marking the downstream packets. 2. Introduction The mechanics of using RSVP [RSVP] signalling and the DCLASS object for requesting and applying the QoS in a differentiated services [DS] network is described fully in [INTDIFF]. It assumes an architecture with RSVP senders and receivers and a differentiated services network somewhere between the sender and the receiver. At least one RSVP aware network element resides in the diff-serv network. This network element interacts with RSVP messages arriving from outside the DS network. The principle use of the DCLASS object is to carry DSCP information between a DS network and upstream nodes that may wish to mark packets with DSCP values. A network element in the DS network determines the value for DSCP which is further carried as a DCLASS object in RSVP RESV message to the sender host. If the network element determines that the request represented by the PATH and RESV messages is admissible to the diff-serv network, a desision is made to mark the arriving data packets for this traffic using MF classification, or to request upstream marking of packets with the appropriate DSCPs. If the network element decides the packets to be marked at the sender host for the data traffic, it adds a DCLASS object in the RSVP RESV message to the host. The use and format of DCLASS object is fully specified in [DCLASS]. There may be situations where the sender host is not capable or may not wish to mark the packets. In the current definition of DCLASS object, the network edge device inserts the DCLASS object in the RSVP RESV message without having any prior knowledge of the host capability whether or not the host can make use of this object. This is one example where the network element needs to know the host capabilities before making a policy decision. Moreover, the definition of DCLASS object allows any DS domain to supply DCLASS object on a flow to the upstream DS domains. A prior knowledge of the upstream DS domain's marking capability could be useful for the downstream DS domain. There could be other scenerios where an advance knowledge of the host or a upstream node's capability may help the network to provide better policy decisions to the end host. Currently, there is no way for the host or network devices to specify their capabilities. The decision where the data packets should be marked can be made at the DS network nodes assuming that the network edge devices have a prior knowledge of the marking capability of the upstream domains. Section 3 of this draft describes two scenarios to explain the use of CAP object in RSVP PATH message. 3. Capability Negotiation The capability object called 'CAP' object can be used as a mechanism for conveying node capabilities or willingness in RSVP messages. As an example, we will focus on the marking capability of nodes throughout this document and define a single bit for host marking information to be carried in the CAP field inside the CAP object of RSVP PATH message. Hamid Expires May, 2001 [Page 2] draft-ietf-issll-rsvp-cap-01.txt November, 2000 However, the CAP is a generic object that can be used to carry any other meaningful capability information in the RSVP PATH message. To explain the use of CAP object in RSVP PATH message, we will describe two scenarios - Host-Edge router interaction - Border Router-Border Router interaction It should be noted that how and when the packets will be marked is a decision governed by the network policies. The network policy domain may or may not trust the end host marking. Hence, even though the network may have supplied the DCLASS object to the end host on request (via CAP) it may overwrite the marking based on the domain policy. 3.1 Host-Edge Router Capbility Negotiation The advance knowledge of the end host's capabilities may help the network edge devices to make policy decisions on end host's requests. These capabilities can be indicated in the RSVP PATH message to the downstream edge devices. The end hosts can be classiffied in two categories: Those capable of marking downstream packets and decide to do so. The other category of hosts either do not have the capability to mark packets or they decide not to mark packets. In either case, the network element needs to know the host packet marking capability/willingness. This information can help the network element to decide whether or not a DCLASS object must be added in a RSVP message for the flow. One way to convey the host capability/willingness to the network is to use the RSVP PATH message. We give examples here to explain the scenarios. If the sender host is ready to mark the downstream traffic (based on the DCLASS provided by the network element), it sets the marking bit of the CAP field inside the CAP object of the RSVP PATH message. On receiving the RSVP message, the network element at the DS edge records the host marking capability as the PATH state. It then resets the marking bit and sends the RSVP message to the downstream nodes. The treatment of the CAP object at the downstream nodes will be explained in next section. For now, consider the RESV message comes back to the edge device, it performs the necessary admission control. If the network element determines that the request represented by the PATH and RESV messages is admissible to the diff-serv network, it adds a DCLASS object after consulting the recorded state. It may decide to overwrite any DCLASS object inserted by the an downstream node/domain based on its own domain policies. This is exactly how the DCLASS object is defined. Another example could be the end host that is not capable of downstream packet marking. This either will not include a CAP object or the host will reset the marking bit of the CAP object as an indication of his unwillingness of packet marking. The network edge router will then know that the upstream node/end host does not require a DCLASS object. The edge router, in this case, would be responsible for marking the downstream packets from the end host. Hamid Expires May, 2001 [Page 3] draft-ietf-issll-rsvp-cap-01.txt November, 2000 3.2 Boundry router-Boundry Router Interaction The CAP object could be carried in the PATH message end-to-end. The RSVP PATH message is generated by the end host. The network edge router 'A' of the DS domain processes the message, resets the marking bit of the CAP object (if it comes as set from the host) and passes the PATH message to the next RSVP Hop. For a DS domain, the boundray router 'B' of the access/stub network receives the RSVP PATH message as next RSVP enabled node (Figure 1). It may set the marking bit again to advertise the marking capability of its own domain. The decision must be governed by the domain policy. The ingress boundary router 'C' of the downstream domain receives the CAP object with the marking bit set providing an indication of the marking capability of the upstream node/domain. It again stores this information as the PATH state, resets the marking bit and passes it to the downstream RSVP enabled network element. The boundary router 'D' of this domain may decide to set the marking bit again based on the domain policy. The PATH message may pass through more domains like this until it is received by the host. The RSVP RESV message is then generated and passed through the same route. The RSVP message arrives at the the router 'C' and it may contain a DCLASS object provided by an downstream node/domain. The PATH state of router 'C' indicates that the upstream node/domain is capable of packet marking and a DCLASS object is to be passed back. The domain policy/admission control decisions of router 'C' may not allow the router to use the same DCLASS value as it received from the downstream. So it may decide to overwrite the DCLASS value. The edge router 'A' may also decide to remark the DCLASS value in the RESV message following its admission control outcome and knowing the end host's willingness for packet marking. Finally, the end host receives the DCLASS value in RESV message and it may start marking the downstream packets with the appropriate DSCP. Once again, It should be noted that how and when the packets will be marked is a decision governed by the network policies. The network policy domain may or may not trust the end host marking. Hence, even though the network may have supplied the DCLASS object to the end host on request (via CAP) it may overwrite the marking based on the domain policy. +----------+ +-----------+ |DS domain | |DS domain | | 1 | | 2 | +----+ +----+ +----+ +----+ +----+ +----+ |Host|-----| A | | B |----| C | | D |---''''''|Host| +----+ +----+ +----+ +----+ +----+ +----+ | | | | | | | | +----------+ +-----------+ Figure 1 4. Format of CAP Object The CAP object has the following format: 0 | 1 | 2 | 3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | C-Num (226) | C-Type=1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CAP field | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Hamid Expires May, 2001 [Page 4] draft-ietf-issll-rsvp-cap-01.txt November, 2000 CAP field: 0x01: D_MARK The host marking capability/willingness identifier. If D_MARK bit is reset, the sender host/upstream node is not able to mark packets If D_MARK bit is set, the sender host/upstream node is able/willing to mark packets Note: D_MARK is a bit in the CAP (capbility) field. 5. Deployment Scenarios There are a number of hosts today which do have the marking capability and they even do not depend on a DCLASS object from the network. The marking is based on a default mapping from requested service type to the DSCP. In this section, we will briefly address the deployment scenarios for such hosts which do mark without signaling network about their marking capability. If a host does not provide a CAP object, then the network edge must be provisioned (or be given policies) as to how it should react. This may be one of: - send a DCLASS object. - install a filter to mark the appropriate flow at the edge. - do both. The problem here is ensuring that the mapping configured in the host matches the allowed mappings configured in the edge router. If there is a mismatch, the edge router will, at best, remark the packets to match its policies (possibly resulting in a treatment different from that expected by the host) or, at worst, mark packets as non-conforming and discard them. The policy may be for a specific host address, for a specific interface, for a specific edge router or for the entire domain. The bottom line is that manual provisioning would be required in the interim until hosts support the CAP option. Once hosts support the CAP option, manual provisioning would no longer be required. In a multi-domain scenario, the boundary router 'B' could be the first and the only router in the first DS domain who is dealing with the CAP/DCLASS objects (maintaining the state information and deciding for a DSCP for the upstream end host). This will allow only one router in a domain with the knowledge of the host's capability and will be the one responsible for deciding/providing a DCLASS object in a RSVP RESV message. In this scenario, the boundary router 'B' becomes the DS edge for the end host. 6. References [INTDIFF], Bernet, Y., Yavatkar, R., Ford, P., Baker, F., Zhang, L., Speer, M., Braden, R., Davie, B., Wroclawski, J., "Integrated Services Operation over Diffserv Networks", Internet Draft, June 1999 [DS] An Architecture for Differentiated Services. S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, RFC 2475, December 1998. Hamid Expires May, 2001 [Page 5] draft-ietf-issll-rsvp-cap-01.txt November, 2000 [RSVP] Braden, R. ed., "Resource ReSerVation Protocol (RSVP) - Functional Specification.", IETF RFC 2205, Sep. 1997. [DCLASS] Bernet, Y., "Format of the RSVP DCLASS Object", IETF , Oct., 1999. 7. Acknowledgments Thanks to Bill Gage, Yoram Bernet, Goran Janevski, Gary Kenward, kwok Ho chan, Muhammad Jaseemuddin and Louis-Nicolas Hamer for reviewing this draft and providing useful input. 8. Author's Address Syed, Hamid Nortel Networks 100 - Constellation Crescent, Nepean, ON K2G 6J8 Phone: (613) 763-6553 Email: hmsyed@nortelnetworks.com 9. Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. 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