HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 09:16:48 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Fri, 18 Jun 1999 17:20:14 GMT ETag: "2e6d8d-2745-376a7fce" Accept-Ranges: bytes Content-Length: 10053 Connection: close Content-Type: text/plain Internet Engineering Task Force Yoshiharu Itoh INTERNET-DRAFT TOYOCOM Expires December, 1999 Configuration of NHRP over Mixed Environment with PVC and SVC 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. To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Abstract This document describes an address resolution process tailored to work under NBMA Next Hop Resolution Protocol (NHRP)[1] over Asynchronous Transfer Mode (ATM) network with mixture of PVC environment and SVC environment. Now consider the case where NHRP clients, each are connected to PVC network, try to communicate each other through SVC network existing on the path between the PVC networks of each client. For this purpose, a straight forward application of resources in PVC can not be possible because of the fixed characteristics of resource in PVC network. Therefore a specific process need to be adopted for deciding virtual path (VP) and virtual connection (VC) necessitated in SVC. Signaling[2] thus generated in SVC by utilizing the resource given from PVC can do this job, and finally the path can be established. Itoh [Page 1] INTERNET-DRAFT Mixed PVP Expires December 1999 The description on the above matters are given here in detail for the network configuration of PVC-SVC-PVC. 1. Introduction Address resolution process applicable to ATM network with mixture of PVC environment and SVC environment is described here in this document. Before going into the description of the process on mixed configuration, a brief view on respective environment will be given below. NHRP[1] specifies an address resolution process on SVC network with plural logically independent IP subnets. In PVC network, address resolution is straight forward because of the existence of rigid correspondence between IP address and VP/VC. Farther details are in NHRP. 1.1 Address Resolution over PVC Network In PVC network, virtual connection is explicitly established in advance to each NHRP Client (NHC), therefore for each initiation of NHRP Resolution Request, NHRP server (NHS) must respond to source NHC with VP/VC corresponding to destination protocol address. The source NHC, then apply this specific VP/VC decided by the destination NHS to establish the network communication. 1.2 Address Resolution over SVC Network Contrast to PVC network, SVC network is characterized by utilizing Signaling[2] to establish the necessitated resource for communication. In SVC network, to each initiation of NHRP Resolution Request in source NHC, destination NHS must respond to that request with the destination NHC's ATM address as NHRP Resolution Reply. On receiving that NHRP Resolution Reply, source NHC decides VP/VC by utilizing Signaling, that is to say source NHC has a right of decision on resource. For further details on this matter, refer to NHRP[1]. Itoh [Page 2] INTERNET-DRAFT Mixed PVP Expires December 1999 2. Address Resolution over Mixed Environment Here describes address resolution process over network with a mixed configuration of PVC and SVC. 2.1 Constraints on Network Configuration Assume that the network under consideration satisfies the following constraints. NHC is connected directly to PVC. In PVC network, value of VP/VC for IP address is pre-assigned and fixed. $ Source PVC network construct LIS. $ One and only one SVC network that construct LIS can exist on a path. $ Destination PVC network construct LIS. $ From the above, these actual communication network has a path of PVC-SVC-PVC chain. $ Adjoining NHS have already established NHRP connection. 2.2 Address Resolution Process From the constraints of 2.1, address resolution process can be streamed as following. $ Source NHC transmits NHRP Resolution Request. $ Source NHS forwards NHRP Resolution Request to SVC network. $ NHS in SVC network forwards NHRP Resolution Request to destination NHS. $ Destination NHS responds to destination NHC with the assigned VP/VC to that destination NHC and also ATM address of destination NHS through NHRP Resolution Reply packet. $ NHRP Resolution Reply arrives at the source NHS through the path on which the NHRP Resolution Request has been forwarded. $ On the arrival of the NHRP Resolution Reply, source NHS initiates Signaling toward destination NHS using the ATM address and VP/VC given in that NHRP Resolution Reply Packet. Itoh [Page 3] INTERNET-DRAFT Mixed PVP Expires December 1999 $ The VP/VC assigned in that reply packet is used in SVC network. $ Source NHS responds to the source NHC with the VP/VC by NHRP Resolution Reply packet. $ Then, source NHC starts communication using that VP/VC in reply packet. 2.3 Characterizing Factor of this Process Through the process described in 2.2, destination NHS decides the VP/VC available between NHCs in a mixed environment. This is just the same way as they are in a ordinary PVC network. In NHRP as was described in 2.2, source NHC decides VP/VC even though destination NHC can receive only assigned VP/VC. This is one of the characterizing factor of this process. Using an assigned VP/VC in Signaling is also a specific in this process, contrast to this, in ordinary way of Signaling, an initiating node decides VP/VC and only if it is accepted at the destination node, network communication can be established. It can be recognized that using assigned VP/VC in Signaling presents better connectability compared with the ordinary Signaling. By employing the process described, NHS provides a function of address resolution and also of resource management for registered NHCs. Another characterizing factor of this configuration is the simplification of function of NHC by discarding Signaling function. 3. PVC Cut-through This section shows a method of realizing cut-thorough by connecting specific path to PVC network in advance. 3.1 Configuration of specific path network For the specific path network, assume the following specifications. $ There exist LIS-1 and LIS-2 being connected by PVC, and they are connected each other through PVC network. $ NHS of LIS-1 (NHS-1) recognizes NHS of LIS-2 (NHS-2) as its Next Hop. $ NHS-2 recognizes NHS-1 as its Next Hop. Itoh [Page 4] INTERNET-DRAFT Mixed PVP Expires December 1999 $ Our concern is restricted on a communication from NHC of LIS-1 (NHC-1) to NHC of LIS-2 (NHC-2). 3.2 Process of Address Resolution The address resolution, under the specification in 3.1, can be streamed as following. $ NHRP Resolution Request is transmitted from NHC-1 to NHC-2. $ NHS-1 forwards NHRP Resolution Request to NHS-2. $ NHS-2 responds to NHS-1 with VP/VC assigned to NHC-2 through NHRP Resolution Reply. $ NHS-1 responds to NHC-1 with NHRP Resolution Reply from NHS-2. $ NHC-1 initiates communication with NHC-2 by using VP/VC in the NHRP Resolution Reply. 3.3 Advantage of Cut-through Process In case of steadily heavy traffic is anticipated, like in the case of connecting distant LANs together, an ordinary SVC network would cause heavy Signaling load, in such case, an effective solution for the reduction of load, would be to connect LIS by PVC and then apply address resolution process described in 3.2. To do this, the configuration in 3.1 can work well, because target LIS is registered in NHS as a next hop in advance, Address Resolution Request is transferred directly to LIS without transferring to SVC network, so that address resolution load can be greatly reduced. Another advantage of cut-through network application is, to an anticipated traffic, network can prepare resources in advance, so that can offer better service, and also expected to be applicable in the virtual LAN (VLAN) technology. Itoh [Page 5] INTERNET-DRAFT Mixed PVP Expires December 1999 Reference [1] Luciani, J. V., Katz, D., Piscitello, D., and B. Cole, "NBMA Next Hop Resolution Protocol (NHRP).", RFC 2332, Bay Networks, Cisco Systems, Core Competence, Inc., December 1997 [2] ATM Forum, "ATM User-Network Interface (UNI) Specification Version 3.1.", ISBN 0-13-393828-X, Prentice-Hall, Inc., Upper Saddle River, NJ, 07458, September, 1994. Author's Addresses Yoshiharu Itoh TOYO Communication Equipment CO.,LTD 1-1, Koyato 2-choume, Samukawa-machi, Koza-gun, Kanagawa-Pref., JAPAN 253-0192 Phone:+81 467 74 7800 FAX: +81 467 74 5693 Email: y_itoh@toyocom.co.jp Itoh [Page 6]