NSAP Allocation for MAGIC

John Cavanaugh
johnc@networkcs.com
Network Computing Services, Inc.

1.0 Background

This document is the plan for the assignment of ATM addresses within the MAGIC-II network. It is compatible with the proposal made by Rich Verjinski [5] for ATM addressing and hierarchical routing with ATDnet, AAI, MAGIC, and the NASA NREN.

The ATM Forum's specification of the address format for private ATM networks is modeled after the OSI Network Service Access Point (NSAP). NSAPs are designed to be globally unique addresses and contain a number of fields in support of this goal. An NSAP-format ATM address is 20 bytes long, with fields as shown in Figure 1 .

FIGURE 1. ICD ATM Address Format

 

AFI

8 bits

Address Format Identifier; 0x47 for ICD ATM format

ICD

16 bits

International Code Designator; 0x0005 for the US Government

DFI

8 bits

Domain-Specific Part (DSP) Format Identifier; 0x80 for GOSIP Version 2

AA

24 bits

Administrative Authority; 0xFFDC00 for MAGIC

Reserved

16 bits

Reserved for future use

RD

16 bits

Routing Domain identifier

Area

16 bits

Area Identifier

ESI

48 bits

End System Identifier; usually set from the hardware address of the ATM adapter

Sel

8 bits

NSAP Selector; identifies a particular user of the NSAP

2.0 Goals

The goals of MAGIC's ATM address numbering plan are:

3.0 MAGIC Numbering Plan

Allocation of ATM Address Fields

As shown in Figure 1 , the AFI, ICD, DFI, and AA fields of the NSAP are pre-determined. The ESI and Sel fields are specific to the end system being addressed. The Reserved field is best left unused in anticipation of some future assignment, leaving the RD and Area fields for assignment within MAGIC.

The RD field (16 bits) will be used to indicate the site within the MAGIC network. Values are shown in Table 1 below. The Area field (16 bits) will be used to indicate the switch within the site, with values assigned by the various sites. Sites may, at their discretion, subdivide the Area field to add a level of hierarchy within the site. If this is done, we recommend that byte boundaries for subfields be observed.

Assignment of Values

Table 1 shows the values assigned to the RD field of the NSAP, indicating which site an address belongs to.

TABLE 1. RD Values for MAGIC
RD Value
Site

0x0000

Not used

0x0001

Sprint TIOC

0x0002

MSCI

0x0003

EDC

0x0004

KU

0x0005

Sprint ATL

0x0006

LBL

0x0007

SRI, Menlo Park

Values for the Area field are assigned at each site.

4.0 Transition

The transition will proceed in two stages. First, MAGIC switches and hosts will switch to new ATM addresses based on MAGIC's Administrative Authority identifier. After this is complete, MAGIC switches will start using hierarchical routing.

Address Transition

The goal of the first stage of the transition is to change the NSAP addresses used by MAGIC hosts and switches. Three things will have to be changed:

  1. The NSAP prefixes of the ATM switches,
  2. The NSAP prefixes of the ATM hosts (note that many hosts use ILMI to determine their NSAP prefixes, so will not require any configuration changes),
  3. The NSAP address of the ATMARP server.

During this stage, the MAGIC-II network will be configured as a single ForeThought PNNI peergroup using the default peer group mask (0). During the transition, communication which uses the UNI signalling protocols will be disrupted, but SPANS-based communication will not.

The section below describes the configuration changes that will be necessary on MAGIC ATM switches and hosts.

Configuration Changes for Address Migration

A number of configuration changes will have to be made for MAGIC to use the new ATM address numbering plan. They are described in the following sections.

ATM switch configurations will require changes to set the appropriate NSAP address prefix and to use the new ATMARP server address. The configuration commands to effect these changes on FORE ATM switches are:

  • Configure each switch to use the new address:

> config topology forepnni

> prefix 0x47.0005.80.ffdc00.0000.rrrr.aaaa [Set NSAP prefix]

where:

rrrr specifies the RD field of the NSAP address, as specified in See Also: Assignment of Values

aaaa specifies the Area field of the NSAP address, as specified in See Also: Assignment of Values

  • Configure the new ATMARP server address:

> configuration atmarp arpserver

> set 0x47.0005.80.ffdc00.0000.0002.0001.0020481a0170.00 qaa0 [Set ATMARP server address]

> configuration ip

> admin qaa0 down [Shut down and restart IP interface]

> admin qaa0 upinterface

  • Change static NSAP routes for hosts which don't use ILMI:

> configuration nsap route

> delete 47000580ffe1000000f21a01700020481a017000 152 1a4 0 [Delete old NSAP address]

> new 47000580ffdc000000000200010020481a017000 152 1a4 0 [Install new NSAP address]

The author has no experience with ATM switches not manufactured by FORE, so cannot give examples for reconfiguring them.

Host configurations will require changes to set the NSAP prefix to match that of the ATM switch the host is attached to, and to change to the address of the ATMARP server.

Examples of configuration commands to effect these changes are given below.

  • Configure NSAP prefix for hosts which do not have the NSAP prefix set via ILMI. For hosts that use HARP:

atm set prefix hfa0 0x47.0005.80.ffdc00.0000.0002.0001

  • Configure a new address for the ATMARP server in MAGIC-II hosts. For hosts that use ForeThought:

atmarp -p 47000580ffdc000000000200010020481a017000 qaa0

For hosts that use HARP:

atm set arpserver uni0 0x47.0005.80.ffdc00.0000.0002.0001.0020481a0170.00

Hierarchical Routing Migration

During the second stage of the transition, the MAGIC-II network will be reconfigured as a set of ForeThought PNNI peer groups, one at each site.

Within a peergroup, all ATM addresses start with a common prefix. For MAGIC, this will be the NSAP address from the start through the RD field, or 88 bits. The Area field is available for use within the peer group.

Also, border switches, switches which are adjacent to one or more switches which are not part of the local site's peer group, will have to be configured. When border functionality is turned on, the border switches will summarize the site's information when disseminating it to other switches and ensure that appropriate filtering is applied to topology information entering the site.

All ATM switches which have links to other MAGIC sites or to non-MAGIC networks will act as border switches, summarizing their peer groups to off-site networks.

Configuration Changes for Hierarchical Routing Migration

After the ATM addresses are changed, MAGIC can start to use hierarchical routing. Configuration changes to effect this change are described below.

ATM switch configurations will require changes to set the peer group mask and to turn on border switch functionality. The configuration commands to effect these changes on FORE ATM switches are:

  • Configure each switch to use the appropriate peer group mask:

> config topology forepnni

> pgmask 88 [Set peer group mask length]

  • Configure border switches:

> config topology forepnni

> border on [Turn on border functionality]

Note: when border switch functionality is enabled, it must be configured at both ends of the link at the same time. This will require coordination between MAGIC sites as well as between MAGIC and the other networks MAGIC is connected to.

The switch prefix mask should be left at its default value (104 bits).

It is important to turn on hierarchical routing at leaf nodes of the network first and then to work in towards the center to avoid partitioning the default peergroup. Accordingly, hierarchical routing should be enabled first at MSCI, EDC, and MAGIC's west coast sites, and only enabled at the TIOC after the edge sites have made the transition.

Host configurations will not require any changes in the second phase.

Transition Plan

This section lists the steps to be executed in order to migrate MAGIC to the new NSAP addresses.

  1. Reconfigure Gandalf.MSCI.magic.net, the ATM switch at MSCI, to use the appropriate new address,
  2. Reconfigure MAGIC UNI hosts to use Gandalf's new NSAP address as their ATMARP server address,
  3. Reconfigure Merlin.EDC.magic.net, the ATM switch at EDC, to use the appropriate new address,
  4. Other sites may migrate to the new ATM addresses as they find it convenient.

Once the address migration is complete, hierarchical routing can be enabled by the following steps.

  1. Turn on hierarchical routing at MSCI,
  2. Turn on hierarchical routing at EDC,
  3. Turn on hierarchical routing at SRI and LBL,
  4. Turn on hierarchical routing at the Sprint ATL,
  5. Turn on hierarchical routing at the TIOC.

References

    [1] The ATM Forum, ATM User-Network Interface Specification, Version 3.0, Englewood Cliffs, NJ: PTR Prentice Hall, September 10, 1993.

    [2] The ATM Forum, Private Network-Network Interface Specification Version 1.0 (PNNI 1.0), af-pnni-0055.000, The ATM Forum, March 1996.

    [3] Colella, Richard, Ella Gardner, and Ross Callon, Guidelines for OSI NSAP Allocation in the Internet, RFC 1237, IETF, July 1991.

    [4] FORE Systems, Inc., ForeThought PNNI Network Design Guide, Version 1.1, FORE Systems, Inc., October 1, 1996.

    [5] Verjinski, Rich, Proposal for ATM Routing and Addressing Changes on the ATDnet/AAI/MAGIC/NREN Network(s), FORE Systems, Inc., 25 February 1997.