Internet DRAFT - draft-ietf-ion-nhrp-mixed-pvp
draft-ietf-ion-nhrp-mixed-pvp
Internet Engineering Task Force Yoshiharu Itoh
INTERNET-DRAFT TOYOCOM
<draft-ietf-ion-nhrp-mixed-pvp-00.txt>
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.
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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.
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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].
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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.
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$ 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.
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$ 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.
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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
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