Internet Engineering Task Force RSVP WG INTERNET-DRAFT A. Terzis <draft-ietf-rsvp-tunnel-01.txt> UCLA J. Krawczyk ArrowPoint Communications J. Wroclaswki MIT LCS L. Zhang UCLA August 1998 Expiration: February 1999 RSVP Operation Over IP Tunnels <draft-ietf-rsvp-tunnel-01.txt> Status of this Memo This document is an Internet-Draft. Internet-Drafts are working docu- ments of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working doc- uments 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." To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). This document is a product of the RSVP working group of the Internet Engineering Task Force. Comments are solicited and should be addressed to the working group's mailing list at rsvp@isi.edu and/or the author(s). draft-ietf-rsvp-tunnel-01.txt [Page 1]
INTERNET-DRAFT August 1998 Abstract This document describes an approach for providing RSVP protocol services over IP tunnels. We briefly describe the problem, the characteristics of possible solutions, and the design goals of our approach. We then pre- sent the details of an implementation which meets our design goals. 1. What's changed Note: The changes described here are from a interim version of the draft that was not published as an IETF Internet Draft but can be found at UCLA IRL's web site (http://irl.cs.ucla.edu). We choose to do since there is small resemblance of this draft to the previously published version (01). - The definitions of a type 1 tunnel has changed to mean that at least one of the tunnel endpoints does not support RSVP Tunnels. - Definitions of type 2 and 3 tunnels were also changed. - The SESSION_ASSOC object is now carried by end-to-end PATH messages and not by Tunnel PATH messages. - The C-type for the SESSION_ASSOC message is 0. - The title of paragraph 4.2 was changed to reflect the reorganization of the whole fourth paragraph. - Paragraph 4.2.1 was radically changed. - Paragraph 4.2.2 was changed to match the changes in 4.2.1 - Paragraph 4.2.3 was corrected. Now includes two cases for refreshing of tunnel RESV state for "hard" and "soft" pipes. - Paragraphs 4.3, 4.3.1, 4.3.2, 4.4 (the ones talking about handling of dynamic tunnels) were removed. It was felt that there was a lot of over- lap between those paragraphs and the corresponding ones talking about configured tunnels. The handling of configured and dynamic tunnels are described in paragraphs 4.2 - 4.2.3. - Paragraph 6.1 now contains the source UDP port assigned by IANA. - The first part of paragraph 6.3 (ICMP messages) was removed. - Paragraph 8 (RSVP Support over Multicast Tunnels) is complete updated. draft-ietf-rsvp-tunnel-01.txt [Page 2]
INTERNET-DRAFT August 1998 - A new Paragraph 9 was added containing the extensions needed to the RSVP/Routing Interface by RSVP Tunnels. - Several wording changes were made. 2. Introduction IP-in-IP "tunnels" have become a widespread mechanism to transport data- grams in the Internet. Typically, a tunnel is used to route packets through portions of the network which do not directly implement the desired service (e.g. IPv6), or to augment and modify the behavior of the deployed routing architecture (e.g. multicast routing, mobile IP, Virtual Private Net). Many IP-in-IP tunneling protocols exist today. [IP4INIP4] details a method of tunneling using an additional IP4 header. [MINENC] describes a way to reduce the size of the "inner" IP header used in [IP4INIP4] when the original datagram is not fragmented. The generic tunneling method in [IPV6GEN] can be used to tunnel either IPv4 or IPv6 packets within IPv6. [RFC1933] describes how to tunnel IPv6 datagrams through IPv4 networks. [RFC1701] describes a generic routing encapsulation, while [RFC1702] applies this encapsulation to IPv4. Finally, [ESP] describes a mechanism that can be used to tunnel an encrypted IP data- gram. >From the perspective of traditional best-effort IP packet delivery, a tunnel behaves as would any other link. Packets enter one end of the tunnel, and are delivered to the other end unless resource overload or error causes them to be lost. The RSVP setup protocol [RSVP] is one component of a framework designed to extend IP to support multiple, controlled classes of service over a wide variety of link-level technologies. To deploy this technology with maximum flexibility, it is desirable for tunnels to act as RSVP-control- lable links within the network. A tunnel, and in fact any sort of link, may participate in an RSVP- aware network in one of three ways, depending on the capabilities of the equipment from which the tunnel is constructed and the desires of the operator. 1. The (logical) link may not support resource reservation or quality- of- service control at all. This is a best-effort link. We refer to this as a best-effort or type 1 tunnel in this note. 2. The (logical) link may be able to promise that some overall level of resources is available to carry traffic, but not to allocate draft-ietf-rsvp-tunnel-01.txt [Page 3]
INTERNET-DRAFT August 1998 resources specifically to individual data flows. A configured resource allocation over a tunnel is an example of this. We refer to this case as a type 2 tunnel in this note. 3. The (logical) link may be able to make reservations for individual end-to-end data flows. We refer to this case as a type 3 tunnel in this note. The first type tunnels exist when at least one of the routers comprising the tunnel endpoints does not support the scheme we describe here. In this case, the tunnel acts as a best-effort link. Our goal is simply to make sure that RSVP messages traverse the link correctly, and the pres- ence of the non-controlled link is detected, as required by the inte- grated services framework. When the two end points of the tunnel are capable of supporting RSVP over tunnels, we would like to have proper resources reserved along the tunnel. Depending on the requirements of the situation, this might mean that one client's data flow is placed into a larger aggregate reserva- tion (type 2 tunnels) or that possibly a new, separate reservation is made for the data flow (type 3 tunnels). Note that an RSVP reservation between the two tunnel end points does not necessarily mean that all the intermediate routers along the tunnel path support RSVP, this is equiva- lent to the case of an existing end-to-end RSVP session transparently passing through non-RSVP cloud. Currently, however, RSVP signaling over tunnels is not possible. RSVP packets entering the tunnel are encapsulated with an outer IP header that has a protocol number other than 46 (e.g. it is 4 for IP-in-IP encapsulation) and do not carry the Router-Alert option, making them virtually "invisible" to RSVP routers between the two tunnel endpoints. Moreover, current IP-in-IP encapsulation scheme adds only an IP header as the external wrapper, thus it is impossible to distinguish between packets that use reservations from those that don't, or packets belong- ing to different RSVP sessions, while they are in the tunnel, because no distinguishing information such as a UDP port is available in the encap- sulation. This document describes an IP tunneling enhancement mechanism that allows RSVP to make reservations across all IP-in-IP tunnels. This mechanism is capable of supporting both type 2 and type 3 tunnels, as described above, and requires minimal changes to both RSVP and other parts of the integrated services framework. draft-ietf-rsvp-tunnel-01.txt [Page 4]
INTERNET-DRAFT August 1998 3. The Design 3.1. Design Goals Our design choices are motivated by several goals. * Co-existing with most, if not all, current IP-in-IP tunneling schemes. * Limiting the changes to the RSVP spec to the minimum possible. * Limiting the necessary changes to only the two end points of a tun- nel. This requirement leads to simpler deployment, lower overhead in the intermediate routers, and less chance of failure when the set of intermediate routers is modified due to routing changes. * Supporting correct inter-operation with RSVP routers that have not been upgraded to handle RSVP over tunnels and with non-RSVP tunnel endpoint routers. In these cases, the tunnel behaves as a non-RSVP link. 3.2. Basic Approach The basic idea of the method described in this document is to recur- sively apply RSVP over the tunnel portion of the path. In this new ses- sion, the tunnel entry point Rentry sends PATH messages and the tunnel exit point Rexit sends RESV messages to reserve resources for the end- to-end sessions over the tunnel. We discuss next two different aspects of the design: how to enhance an IP-in-IP tunnel with RSVP capability, and how to map end-to-end RSVP sessions to a tunnel session. 3.2.1. To establish a RSVP reservation over a unicast IP-in-IP tunnel, we made the following design decisions: Set up a Fixed-Filter style unicast reservation between the two end points of the tunnel. Packets that do not require reservations are encapsulated in the normal way, e. g. being wrapped with an IP header only, specifying the tunnel entry point as source and the exit point as destination. Data packets that require resource reservations within a tunnel must have some attribute, other than IP addresses, visible to the intermedi- ate routers, so that the routers may distinguish between packets that use a reservation from others that do not, and if more than one draft-ietf-rsvp-tunnel-01.txt [Page 5]
INTERNET-DRAFT August 1998 reservation exists, which one the packets belong to. To allow intermediate routers to use standard RSVP filterspec handling, we choose to encapsulate such data packets by prepending an IP and a UDP header, and to use UDP port numbers to distinguish packets of different RSVP sessions. Figure 1 shows an RSVP over a tunnel where Rentry is the tunnel entry router which encapsulates data into the tunnel. Some number of interme- diate routers forward the data across the network based upon the encap- sulating IP header added by Rentry. Rexit is the endpoint of the tun- nel. It decapsulates the data and forwards it based upon the original, "inner" IP header. ........... ............... ............. : _______ : : _____ : Intranet :--| Rentry|===================|Rexit|___:Intranet : |_______| : : |_____| : ..........: : Internet : :........... :.............. |___________________| Figure 1. An example IP Tunnel 3.2.2. Figure 2 shows a simple topology with a tunnel and a few hosts. The sending hosts H1 and H3, may be one or multiple IP hops away from Ren- try; the receiving hosts H2 and H4 may also be either one or multiple IP hops away from Rexit. H1 H2 : : : : +--------+ +---+ +---+ +---+ +-------+ | | | | | | | | | | H3... | Rentry |===================================| Rexit |..... H4 | | | | | | | | | | +--------+ +---+ +---+ +---+ +-------+ Figure 2: An example end-to-end path with a tunnel in the middle. draft-ietf-rsvp-tunnel-01.txt [Page 6]
INTERNET-DRAFT August 1998 An RSVP session may be in place between endpoints at hosts H1 and H2. We refer to this session as the "end-to-end" or "original" session, and to its PATH and RESV messages as the end-to-end messages. A RSVP ses- sion may be in place between Rentry and Rexit to provide resource reser- vation over the tunnel. We refer to this as the tunnel RSVP session, and to its PATH and RESV messages as the tunnel or tunneling messages. A tunnel RSVP session may exist independently from any end-to-end ses- sions. For example through network management interface one may create a RSVP session over the tunnel to provide QoS support for data flow from H3 to H4, although there is no end-to-end RSVP session between H3 and H4. When an end-to-end RSVP session crosses a RSVP-capable tunnel, there are two cases to consider in designing mechanisms to support an end-to-end reservation over the tunnel: mapping the E2E session to an existing tun- nel RSVP session, and creating a new tunnel RSVP session for each end- to-end session. In either case, the picture looks like a recursive application of RSVP. The tunnel RSVP session views the two tunnel end- points as two end hosts with a unicast Fixed- Filter style reservation in between. The original, end-to-end RSVP session views the tunnel as a single (logical) link on the path between the source(s) and destina- tion(s). When an end-to-end RSVP session crosses a RSVP-capable tunnel, it is necessary to coordinate the actions of the two RSVP sessions, to deter- mine whether or when the tunnel RSVP session should be created and torn down, and to correctly transfer error and ADSPEC information between the two RSVP sessions. We made the following design decision: * End-to-end RSVP messages being forwarded through a tunnel are encapsulated in the same way as normal IP packets, e.g. being wrapped with the tunnel IP header only, specifying the tunnel entry point as source and the exit point as destination. 3.3. Major Issues As IP-in-IP tunnels are being used more widely for network traffic man- agement purposes, it is clear we must support type 2 tunnels (tunnel reservation for aggregate end-to-end sessions). Furthermore, we should allow more than one reservation to be made over an IP-in-IP tunnel. Whether it is necessary to support type 3 tunnels (per end-to-end ses- sion tunnel reservation) is a policy issue that should be left open. Our design supports both cases. If there is only one RSVP session configured over a tunnel, then all the draft-ietf-rsvp-tunnel-01.txt [Page 7]
INTERNET-DRAFT August 1998 end-to-end RSVP sessions (that are allowed to use this tunnel session) will be bound to this configured tunnel session. However given more than one RSVP sessions are allowed over an IP tunnel, a second design issue is how the association, or binding, between an original RSVP reservation and a tunnel reservation is created and conveyed from one end of the tunnel to the other. The entry router Rentry and the exit router Rexit must agree on these associations so that changes in the original reservation state can be correctly mapped into changes in the tunnel reservation state, and that errors reported by intermediate routers to the tunnel end points can be correctly transformed into errors reported by the tunnel endpoints to the end-to-end RSVP session. We require that this association mechanism work for both the case of bundled reservation over a tunnel, and the case of one-to-one mapping between original and tunnel reservations. In our scheme the association is created when a tunnel entry point first sees an end-to-end session's PATH message and either sets up a new tun- nel session, or adds to an existing tunnel session. This new associa- tion must be conveyed to Rexit, so that Rexit will know how to process arriving RESV messages from the original reservation. This information includes the identifier and certain parameters of the tunnel session, and the identifier of the end-to-end session to which the tunnel session is being bound. In our scheme, individual tunnel sessions are identified primarily by the source port value. In our scheme, all RSVP sessions between the same two routers Rentry and Rexit will have identical values for source IP address, destination IP address, and destination UDP port number, an individual session is identified primarily by the source port value. We identified three possible choices for a binding mechanism: 1. Define a new RSVP message that is exchanged only between two tunnel end points to convey the binding information. 2. Define a new RSVP object to be attached to end-to-end PATH messages at Rentry, associating the end-to-end session with one of the tun- nel session. This new object is interpreted by Rexit associating the end-to-end session with one of the tunnel sessions generated at Rentry. 3. Apply the same UDP encapsulation to the end-to-end PATH messages as to data packets of the session. When Rexit decapsulates the PATH message, it deduces the relation between the source UDP port used in the encapsulation and the RSVP session that is specified in the original PATH message. The last approach above does not require any new design. However it requires additional resources to be reserved for PATH messages (since they are now subject to the tunnel reservation). It also requires a draft-ietf-rsvp-tunnel-01.txt [Page 8]
INTERNET-DRAFT August 1998 priori knowledge of whether Rexit supports RSVP over tunnels by UDP encapsulation. If Rentry encapsulates all the end-to-end PATH messages with the UDP encapsulation, but Rexit does not understand this encapsu- lation, then the encapsulated PATH messages will be lost at Rexit. On the other hand, options (1) (2) can handle this case transparently. They allow Rexit to pass on end-to-end PATHs received via the tunnel (because they are decapsulated normally), while throwing away the tunnel PATHs , all without any additional configuration. We chose Option (2) because it is simpler. The new object, called SESSION_ASSOC, is defined with the following for- mat: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | length | class | c-type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | SESSION object (for the end-to-end session) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Sender FILTER-SPEC (for the tunnel session) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ SESSION_ASSOC Object The semantics of a SESSION_ASSOC object are that the end-to-end SESSION contained in the object is to be mapped to the tunnel session contained at the same object. The length field contains the size of the SESSION_ASSOC object in bytes. Class=192. Ctype should be sent as zero and ignored on receipt. As we mentioned above, a tunnel session is identified primarily by source port. This is why we use a Sender Filter-Spec for the tunnel ses- sion, in the place of a SESSION object. The packet exchanges must follow the following constraints: draft-ietf-rsvp-tunnel-01.txt [Page 9]
INTERNET-DRAFT August 1998 1. Rentry sends tunnel PATH messages in the standard RSVP format which is understood by all RSVP routers and ignored by non-RSVP Rexit router. 2. Rexit sends tunnel session RESV messages only if the tunnel-session PATH state is present. 3. Rentry UDP-encapsulates arriving packets only if a corresponding tunnel session reservation is actually in place for the packets. 4. Implementation In this section we discuss several cases separately starting from the simplest to the more complex scenarios. 4.1. Single Configured RSVP Session over an IP-in-IP Tunnel Treating the two tunnel ends as a source and destination host, one eas- ily sets up a FF-style reservation in between. Now the question is what kind of filterspec to use for the tunnel reservation, which directly relates to how packets get encapsulated over the tunnel. We discuss two cases below. 4.1.1. In the Absence of End-to-End RSVP Session If all the packets traversing a tunnel can use the reserved resources, then the current IP-in-IP encapsulation could suffice. The RSVP session over the tunnel simply specifies a FF style reservation (with zero port number) with Rentry as the source address and Rexit as the destination address. However if only part of the packets traversing the tunnel can use the reservation, we encapsulate the qualified packets in IP and UDP. This allows intermediate routers to use standard RSVP filterspec handling without knowing the existence of tunnels. To simplify implementations by reducing special case checking and han- dling, we require that all data packets using reservations be encapsu- lated in IP+UDP. 4.1.2. In the Presence of End-to-End RSVP Session(s) According to the tunnel control policies through some management inter- face, some or all end-to-end RSVP sessions may be allowed to map to this single RSVP session over the tunnel. In this case there is no need to provide dynamic binding information between end-to-end sessions and the draft-ietf-rsvp-tunnel-01.txt [Page 10]
INTERNET-DRAFT August 1998 tunnel session, given the tunnel session is pre-configured thus well- known and there is only one out there. Binding multiple end-to-end sessions to one tunnel session, however, raises a new question of whether the amount of tunnel reservation should/can be adjusted by the sum of the end-to-end sessions mapped onto it. Again the tunnel manager makes such policy decision. We call a tunnel reservation a "hard pipe" if the amount cannot be adjusted, oth- erwise a "soft pipe" if it can be adjusted. Section 4.2.1 explains how the adjustment can be carried out for soft pipes. 4.2. Multiple Configured RSVP Sessions over an IP-in-IP Tunnel Like the case of a single configured RSVP session over a tunnel, it is trivial to set up multiple FF-style reservations between the two tunnel points. However in this case Rentry must carefully encapsulate quali- fied data packets with proper UDP port numbers, so that packets belong- ing to difference tunnel sessions can be distinguished by the intermedi- ate RSVP routers. 4.2.1. In the Absence of End-to-End RSVP Session Nothing more need to be said in this case. Rentry classifies the pack- ets and encapsulates accordingly. Packets with no reservations are encapsulated in IP only, packets qualified for reservations are encapsu- lated in IP+UDP, with the UDP source port value properly set to map to the corresponding tunnel reservation the packet is supposed to use. 4.2.2. In the Presence of End-to-End RSVP Session(s) Now because there are more than one RSVP sessions over the tunnel, one must explicitly bind each end-to-end RSVP session to its corresponding tunnel session. As discussed in Section 2.3, this binding will be pro- vided by the new SESSION_ASSOC object carried in the end-to-end PATH messages. 4.3. Dynamically Created Tunnel RSVP Sessions The only differences between this case and that of 3.2.2 are that: - The tunnel session is created when a new end-to-end session shows up. - There is a one-to-one mapping between the end-to-end and tunnel RSVP sessions, as opposed to possibly many-to-one mapping that is allowed in 3.2.2 case. draft-ietf-rsvp-tunnel-01.txt [Page 11]
INTERNET-DRAFT August 1998 5. RSVP Messages handling over an IP-in-IP Tunnel 5.1. RSVP Messages for Configured Session(s) Over A Tunnel Here one or more RSVP sessions are set up over a tunnel through a man- agement interface. The session reservation parameters never change for a "hard pipe" reservation. The reservation parameters may change for a "soft pipe" reservation. The tunnel session PATH messages generated by Rentry are addressed to Rexit, where they are processed and deleted. 5.2. Handling End-to-End RSVP Messages 5.2.1. Handling End-to-End PATH messages at Rentry When forwarding an end-to-end PATH message, a router acting as the tun- nel entry point, Rentry, takes the following actions. First, it consid- ers the corresponding tunnel session. There are four possible cases: 1. The end-to-end PATH message is a refresh of a previously known end- to-end session. 2. The end-to-end session is new and it "matches" to a configured tun- nel session. 3. The end-to-end session is new and according to the configuration, a new dynamic tunnel session should be created. 4. The end-to-end session is new but according to the tunnel configu- ration, it is not allowed to make a reservation over the tunnel. We describe each of the four cases in the paragraphs that follow. If the PATH message is a refresh of a previously known end-to-end ses- sion, then the association between the end-to-end session and the corre- sponding tunnel session has already been made. If the end-to-end session is new and Rentry finds a match in some man- agement database for an existing configured tunnel session, it binds the new end-to-end session to an existing tunnel session. Before it sends the PATH message, Rentry also checks to see if the sum of all end-to-end session Tspec's exceeds the tunnel session's Tspec. * If not, nothing more needs be done at this time. * If yes, Rentry further checks to see if the tunnel reservation is a hard or soft pipe. For a hard pipe, Rentry sends an alarm message to the tunnel manager. For a soft pipe, it increases the tunnel session Tspec accordingly and includes the new parameters in the draft-ietf-rsvp-tunnel-01.txt [Page 12]
INTERNET-DRAFT August 1998 PATH message and sends it. If on the other hand, the end-to-end session is new, and according to the tunnel policy the new end-to-end RSVP session, represented by this new PATH message, is allowed to set up a new tunnel session, Rentry sets up tunnel session PATH state as if it were a source of data by starting to send tunnel-session PATH messages to Rexit, which is treated as the unicast destination of the data. The Tspec in this new PATH message is computed from the original PATH message by adjusting the Tspec parame- ters to include the tunnel overhead of the encapsulation of data pack- ets. The last case is when the end-to-end session is not allowed to use the tunnel resources. In this case no association is created between this end-to-end session and a tunnel session and no new tunnel session is created. After finding the corresponding tunnel session, Rentry adds the appro- priate SESSION_ASSOC object (with the exception of the case where the end-to-end session is not mapped to a tunnel session, where no SES- SION_ASSOC object is added) to the end-to-end PATH message and and sends it over the tunnel. Nothing needs to be done for the tunnel session, since refreshment of the tunnel session's PATH state is controlled by the RSVP refresh timer at Rentry. When an end-to-end PATH TEAR is received by Rentry, it encapsulates and forwards the message to Rexit, and initiates a PATH TEAR for the corre- sponding tunnel session possibly adjusting the Tspec of the tunnel ses- sion. 5.2.2. Handling End-to-End PATH Messages at Rexit When a new end-to-end session is recognized at Rentry, information is passed to Rexit by a binding object in end-to-end PATH message. Rexit records the association of the tunnel session with that of the end-to- end session, and sets the PHOP of the end-to-end session to Rentry. Rexit also notes the state of non-RSVP flag in the tunnel session PATH messages. Encapsulated end-to-end PATH messages are decapsulated at Rexit. Before further forwarding the message to the next hop along the path to the destination, Rexit finds the corresponding tunnel session's recorded state and turns on the end-to-end PATH message's non-RSVP bit if it was turned on for the tunnel session. If the end-to-end PATH message car- ries an ADSPEC object, Rexit performs composition of the characteriza- tion parameters contained in the ADSPEC. It does this by considering the tunnel session's overall (composed) characterization parameters as the draft-ietf-rsvp-tunnel-01.txt [Page 13]
INTERNET-DRAFT August 1998 local parameters for the logical link implemented by the tunnel, and composing these parameters with those in the end- to-end ADSPEC by exe- cuting each parameter's defined composition function. If Rentry does not support RSVP tunneling, then Rexit will have no PATH state for the tunnel. In this case Rexit simply turns on the non-RSVP bit in the decapsulated end-to-end PATH message and forwards it. 5.2.3. Handling End-to-End RESV messages When forwarding a RESV message upstream, a router serving as the exit router, Rexit, may discover that one of the upstream interfaces is a tunnel. In this case the router performs a number of tests. Step 1: Rexit must determine if there is a tunnel session bound to the end-to-end session given in the RESV message. If not, the tunnel is treated as a non-RSVP link, and Rexit simply forwards the RESV message over the tunnel interface (where it is encapsulated as a normal IP data- gram and forwarded towards Rentry). Step 2: If a bound tunnel session is found, Rexit checks to see if a reservation is already in place for the tunnel session bound to the end- to-end session given in the RESV message. If the arriving end-to-end RESV message is a refresh of existing RESV state, then Rexit sends the original RESV through tunnel interface. For dynamic tunnel sessions, the end-to-end RESV message acts as a refresh for the tunnel session RESV state, while for configured tunnel sessions, reservation state never expires (the amount of resources reserved changes though). If the arriving end-to-end RESV message causes a change in the end-to- end RESV flowspec parameters (either a new or changed end-to-end flow), Rexit updates the tunnel session's flowspec parameters. If the change is an increase and the tunnel session is a "soft pipe", Rexit sends a tunnel session RESV, including a RESV_CONFIRM object. If the increase causes the sum of all end-to-end RESV parameters to exceed that of the tunnel RESV parameters for a "hard pipe", a warning message should be sent to the tunnel manager and a RESV_ERR message with Error Code set to 01 (Admission Control failure), should be sent back to the originator of the end-to-end RESV message. If a RESV CONFIRM response arrives, the original RESV is encapsulated and sent through the tunnel. If the updated tunnel reservation fails, Rexit must send a RESV ERR to the originator of the end-to-end RESV mes- sage, using the error code and value fields from the ERROR_SPEC object of the received tunnel session RESV ERR message. Note that the pre- existing reservations through the tunnel stay in place. Rexit continues draft-ietf-rsvp-tunnel-01.txt [Page 14]
INTERNET-DRAFT August 1998 refreshing the tunnel RESV using the old flowspec. Tunnel session state for a "soft pipe" must also be adjusted when an end-to-end reservation is deleted. The tunnel session gets reduced whenever one of the end-to-end sessions using the tunnel goes away (or gets reduced itself). However even when the last end-to-end session bound to that tunnel goes away, the configured tunnel session remains active, perhaps with a configured minimal flowspec. When an end-to-end RESV TEAR is received by Rexit, it encapsulates and forwards the message to Rentry. If the end-to-end session had created a dynamic tunnel session, then a RESV TEAR for the corresponding tunnel session is send by Rexit. 6. Forwarding Data When data packets arrive at the tunnel entry point Rentry, Rentry must decide whether to forward the packets using the normal IP-in-IP tunnel encapsulation or the IP+UDP encapsulation expected by the tunnel ses- sion. This decision is made by determining whether there is a resource reservation (not just PATH state) actually in place for the tunnel ses- sion bound to the arriving packet, that is, whether the packet matches any active filterspec. If a reservation is in place, it means that both Rentry and Rexit are RSVP-tunneling aware routers, and the data will be correctly decapsu- lated at Rexit. If no tunnel session reservation is in place, the data should be encap- sulated in the tunnel's normal format, regardless of whether end-to-end PATH state covering the data is present. 7. Details 7.1. Selecting UDP port numbers There may be multiple RSVP sessions between the two end points Rentry and Rexit. These sessions are distinguished by the source UDP port. Other components of the session ID, the source and destination IP addresses and the destination UDP port, are identical for all such ses- sions. The source UDP port is chosen by the tunnel entry point Rentry when it establishes the initial PATH state for a new tunnel session. The source UDP port associated with the new session is then conveyed to Rexit by the binding mechanism. draft-ietf-rsvp-tunnel-01.txt [Page 15]
INTERNET-DRAFT August 1998 The destination UDP port used in tunnel sessions is a well known one and has be assigned by IANA (363). 7.2. Error Reporting When a tunnel session PATH message encounters an error, it is reported back to Rentry. Rentry must relay the error report back to the original source of the end-to-end session. When a tunnel session RESV request fails, an error message is returned to Rexit. Rexit must treat this as an error in crossing the logical link (the tunnel) and forward the error message back to the end host. 7.3. ICMP messages Since the UDP encapsulated packets should not be fragmented, tunnel entry routers must support tunnel MTU discovery as discussed in section 5.1 of [IP4INIP4]. 7.4. Tspec and Flowspec Calculations As multiple End-to-End sessions can be mapped to a single tunnel ses- sion, there is the need to compute the "sum" of all the Tspecs from all the senders to the End-to-End sessions. This aggregate Tspec will the Tspec of the representative tunnel session. The same operation needs to be performed for flowspecs of End-to-End reservations arriving at Rexit. These operations are not addressed here but are defined in the specifi- cations of the Controlled-Load and Guaranteed services (found at [RFC2211] and [RFC2212] respectively). 8. IPSEC Tunnels In the case where the IP-in-IP tunnel supports IPSEC (especially ESP in Tunnel-Mode with or without AH) then the Tunnel Session uses the GPI SESSION and GPI SENDER_TEMPLATE/FILTER_SPEC as defined in [RSVPESP] for the PATH and RESV messages. Data packets are not encapsulated with a UDP header since the SPI can be used by the intermediate nodes for classification purposes. Notice that user oriented keying must be used between Rentry and Rexit, so that dif- ferent SPIs are assigned to data packets that have reservation and "best effort" packets, as well as packets that belong to different Tunnel Ses- sions if those are supported. draft-ietf-rsvp-tunnel-01.txt [Page 16]
INTERNET-DRAFT August 1998 9. RSVP Support over Multicast Tunnels In the last version of the draft we said that support for "multicast tunnels" was worthwhile and deserved more investigation. Since then, other people have also proposed the use of multicast tunnels in a VPN scenario (see [VMMT] for example). A multicast tunnel is one that has one entry point and multiple exit points. An RSVP reservation over such a tunnel can be viewed as a simple multicast reservation over the tunnel tree, and can be done with the mechanisms described in this draft in the same way as RSVP over unicast tunnels. However there is a new issue raised by RSVP over multicast tunnels: which data flows can use the tunnel reservations? Are they multicast data flows along the same multicast tree, or unicast data flows that individually use different branches of the tree only? The VPN scenario presents a usage of the latter type only. A VPN topol- ogy is made of a number of sites that are remote to each other but interconnected virtual links (IP-in-IP tunnels). The VPN runs its own routing protocol over this virtual topology to compute the forwarding table for data delivery to all the sites on the VPN. Data packets are unicast-encapsulated when they traverse between sites. To provide assured bandwidth among all the points on the same VPN, a single multi- point SE-style RSVP session can be established over the virtual topol- ogy, and the reserved bandwidth can be used by encapsulated data traffic flows between any points. This decoupling of reservation from usage is totally different from the unicast tunnel case, where RSVP reservation is made between the same tunnel entry and exit routers that data traffic goes through. However from the view of RSVP operations over IP tunnels, a multicast tunnel is not much different from a unicast tunnel. All RSVP daemons participat- ing in the set of tunnel end points join the multicast group (the address of the multicast group is decided by means outside the scope of this draft). To set up duplex reservations over the virtual topology, each multicast tunnel end node behaves both as a sender and as a receiver, thus sending both RSVP PATH and RESV messages to the multicast group. The RSVP session may use either WF or SE style, with all the tunnel end points listed as eligible sources in the latter case (because they each may send encapsulated data packets). Since the RSVP session uses a multicast address, while the data packets that use the reserva- tion are unicast-delivered to individual tunnel endpoints, we resolve this issue by setting the destination address field in the packet filter to wildcard. Different from RSVP support over unicast tunnels, however, it is not feasible to map individual unicast end-to-end RSVP sessions onto a mul- ticast RSVP session, simply because the latter is multicast, thus any draft-ietf-rsvp-tunnel-01.txt [Page 17]
INTERNET-DRAFT August 1998 adjustment of the parameters would change the reservation over the whole multicast tree. Whenever it is necessary to support end-to-end RSVP sessions over tunnels, one should use RSVP tunnel over unicast tunnels. Except VPN, at this time we are not aware of other general uses for RSVP over multicast tunnels that assume data is multicast to all receiving points. (we are aware of the use by mobile IP, which is considered a very special case that is beyond the interest of RSVP standardization). 10. Extensions to the RSVP/Routing Interface [RSVP] states that through the RSVP/Routing Interface, the RSVP daemon must be able to learn the list of local interfaces along with their IP addresses. In the RSVP Tunnels case, the RSVP daemon needs also to learn which of the local interface(s) is (are) IP-in-IP tunnel(s) having the capabilities described here. This can be done by setting a special flag for tunnel interfaces in the response from the routing protocol. In the paragraphs that follow we present, as an example, the modifications needed in one of the existing RSVP/Routing Interfaces to support RSVP Tunnels. One particular routing interface for RSVP, called RSRR, is described in [RSRR]. Using RSRR, an RSVP daemon makes an Interface Query to the rout- ing protocol asking for the list of local interfaces. A list of the local interfaces is provided as a reply to this query. The format of the Interface Reply is shown in the following figure. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Type | Flags | Num | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vif ID-1 |Vif Threshold-1| Prefix | Vif Status-1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Family | Address Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vif Local Address-1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |... | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vif ID-N |Vif Threshold-N| Prefix | Vif Status-N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Family | Address Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vif Local Address-N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ draft-ietf-rsvp-tunnel-01.txt [Page 18]
INTERNET-DRAFT August 1998 The bit vector represents the vif status: +-+-+-+-+-+-+-+-+ | |T|N|P|U|M| +-+-+-+-+-+-+-+-+ Where: N = 1 if notification will be made in case of vif changes. P = 1 if vif is physical interface, 0 if it is virtual. U = 1 if vif is unicast-disabled, 0 if it is enabled. M = 1 if vif is multicast-disabled, 0 if it is enabled. What we propose is adding a new bit T in the vif status bit flag, where T=1 if the interface is a RSVP Tunnel, or 0 otherwise. 11. Security Considerations The introduction of RSVP Tunnels raises no new security issues other than those associated with the use of RSVP and tunnels. Regarding RSVP, the major issue is the need to control and authenticate access to enhanced qualities of service. This requirement is discussed further in [RSVP]. [RSVPCRYPTO] describes the mechanism used to protect the integrity of RSVP messages carrying the information described here. The security issues associated with IP-in-IP tunnels are discussed in [IPINIP4] and [IPV6GEN]. 12. References [ESP] R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 1827, August, 1995. [IGMPv3] B. Cain, S. Deering, A. Thyagarajan, "Internet Group Management Protocol, Version 3", Internet Draft draft-ietf-idmr-igmp-v3-00.txt, November 1997. [IP4INIP4] C. Perkins, "IP Encapsulation within IP", RFC 2003, October, 1996. [IPV6GEN] A. Conta, S. Deering, "Generic Packet Tunneling in IPv6 Speci- fication", Internet Draft draft-ietf-ipngwg-ipv6-tunnel-08.txt, January, 1998. [MINENC] C. Perkins, "Minimal Encapsulation within IP", RFC 2004, draft-ietf-rsvp-tunnel-01.txt [Page 19]
INTERNET-DRAFT August 1998 October, 1996. [RFC1701] S. Hanks, T. LI, D. Farinacci, P. Traina, "Generic Routing Encapsulation (GRE)", RFC 1701, October, 1994. [RFC1702] S. Hanks, T. LI, D. Farinacci, P. Traina, "Generic Routing Encapsulation over IPv4 Networks", RFC 1702, October, 1994. [RFC1933] R. Gilligan, E. Nordmark, "Transition Mechanisms for IPv6 Hosts and Routers", RFC 1933, April, 1996. [RFC2211] J. Wroclawski, "Specification of the Controlled-Load Network Element Service", RFC2211, September, 1997. [RFC2212] S. Shenker, C. Partridge, R. Guerin, "Specification of the Guaranteed Quality of Service", RFC2212, September, 1997. [RSRR] D. Zappala, J. Kann, "RSRR: A Routing Interface for RSVP", Inter- net Draft, draft-ietf-rsvp-routing-02.txt, July 1998. [RSVP] R. Braden, L. Zhang, S. Berson, S. Herzog, S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205 , September, 1997. [RSVPESP] L. Berger, T. O'Malley, "RSVP Extensions for IPSEC Data Flows", RFC 2207, September, 1997. [RSVPCRYPTO] F. Baker, "RSVP Cryptographic Authentication", Internet Draft, draft-ietf-rsvp-md5-05.txt, August 1997. [VMMT] S. Pegrum, D. Jamieson, M. Yuen, "VPN Multipoint to Multipoint Tunnel Protocol (VMMT)", Internet Draft draft-pegrum-vmmt-00.txt, March 1998. 13. Authors' Addresses John Krawczyk ArrowPoint Communications 235 Littleton Road Westford, Massachusetts 01886 Phone: 978-692-5875 x27 Email: jjk@tiac.net John Wroclawski MIT Laboratory for Computer Science draft-ietf-rsvp-tunnel-01.txt [Page 20]
INTERNET-DRAFT August 1998 545 Technology Sq. Cambridge, MA 02139 Phone: 617-253-7885 Fax: 617-253-2673 (FAX) EMail: jtw@lcs.mit.edu Lixia Zhang UCLA 4531G Boelter Hall Los Angeles, CA 90095 Phone: 310-825-2695 EMail: lixia@cs.ucla.edu Andreas Terzis UCLA 4677 Boelter Hall Los Angeles, CA 90095 Phone: 310-267-2190 Email: terzis@cs.ucla.edu draft-ietf-rsvp-tunnel-01.txt [Page 21]
