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Guidelines for Next Hop Client (NHC) Developers (RFC2583)

IP.com Disclosure Number: IPCOM000003170D
Original Publication Date: 1999-May-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 8 page(s) / 20K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Carlson: AUTHOR [+2]

Abstract

This document provides guidelines for developers of the Next Hop Resolution Protocol Clients (NHC). It assumes that the clients are directly connected to an ATM based NBMA network. The same principles will apply to clients connected to other types of NBMA networks. The intent is to define the interaction between the NHC code and the TCP/IP protocol stack of the local host operating system. The NHC is capable of sending NHRP requests to a Next Hop Resolution Protocol Server (NHS) to resolve both inter and intra LIS addresses. The NHS reply may be positive (ACK) indicating a short-cut path is available or negative (NAK) indicating that a shortcut is not available and the routed path must be used. The NHC must cache (maintain state) for both the ACK and NAK replies in order to use the correct shortcut or routed path. The NAK reply must be cached to avoid making repeated requests to the NHS when the routed path is being used.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 15% of the total text.

Network Working Group R. Carlson

Request for Comments: 2583 ANL

Category: Informational L. Winkler

ANL

May 1999

Guidelines for Next Hop Client (NHC) Developers

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard of any kind. Distribution of this

memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1999). All Rights Reserved.

1. Abstract

This document provides guidelines for developers of the Next Hop

Resolution Protocol Clients (NHC). It assumes that the clients are

directly connected to an ATM based NBMA network. The same principles

will apply to clients connected to other types of NBMA networks. The

intent is to define the interaction between the NHC code and the

TCP/IP protocol stack of the local host operating system. The NHC is

capable of sending NHRP requests to a Next Hop Resolution Protocol

Server (NHS) to resolve both inter and intra LIS addresses. The NHS

reply may be positive (ACK) indicating a short-cut path is available

or negative (NAK) indicating that a shortcut is not available and the

routed path must be used. The NHC must cache (maintain state) for

both the ACK and NAK replies in order to use the correct shortcut or

routed path. The NAK reply must be cached to avoid making repeated

requests to the NHS when the routed path is being used.

2. Overview

In the Classical IP over ATM model [1], an ATM attached host

communicates with an ATMARP server to resolve IP to ATM address

semantics. This model supports the concept of a Logical IP Subnet

(LIS) with intra LIS communications using direct PVCs/SVCs and inter

LIS communications using IP routers to forward packets. This model

easily maps to the conventional LAN model of subnets and routers.

The Next Hop Resolution Protocol (NHRP) [2] defines how the LIS model

can be modified to allow direct ATM SVCs (shortcut paths) for inter

LIS traffic. With NHRP, nodes directly attached to an ATM network

can bypass the IP routers and establish a direct switched virtual

circuit to improve performance when needed.

The NHS code replaces the ATMARP code in the ATMARP server. Each NHS

serves a set of destination client hosts and cooperates with other

NHSs to resolve NHRP next hop requests within their own logical ATM

network. The NHC to NHS and NHS to NHS protocol interactions are

described in [2]. Other documents in the NHRP series define the

general applicability [3] and the transition from ATMARP servers to

NHSs [4].

The NHC code replaces the ATMARP code in the local workstations.

This code will take the destination IP address and map it into the

ATM End Station Address (AESA) for bo...