************************************************************************ DDN MGT Bulletin 116 DISA DDN Defense Communications System 10 February 1993 Published by: DDN Network Info Center (NIC@NIC.DDN.MIL) (800) 365-3642 DEFENSE DATA NETWORK MANAGEMENT BULLETIN The DDN MANAGEMENT BULLETIN is distributed online by the DDN Network Information Center under DISA contract as a means of communicating official policy, procedures and other information of concern to management personnel at DDN facilities. Back issues may be read through the TACNEWS server ("@n" command at the TAC) or may be obtained by FTP (or Kermit) from the NIC.DDN.MIL host [192.112.36.5] using login="anonymous" and password="guest". The pathname for bulletins is ddn-news/ddn-mgt-bulletin-nn.txt (where "nn" is the bulletin number). ************************************************************************ New Core Routing Servers and Need for Migration from EGP to BGP 1. This message addresses the deployment of new core routing servers (BBN T/20s) and the need for MILNET subscriber gateways to transition from using the External Gateway Protocol (EGP) to using the new Border Gateway Protocol (BGP) to gather routing information. DISA strongly recommends BGP capability be in place by July, 1993. The following topics will be addressed: - Reasons for the need to switch from EGP to BGP - Operational differences between EGP and BGP - Required revision levels for software in subscriber gateways - Configuration changes required in subscriber gateways - Impact on gateways if they do not move from EGP to BGP - Contact person for further assistance. 2. Currently, approximately 420 MILNET gateways exchange EGP information with the Mailbridges. Based on this and historical data on the number of MILNET gateways, and assuming that the growth rate does not change abruptly, it is currently projected that the number of MILNET gateways will reach 510 by September 1993. EGP propagates reachability information for a maximum of 510 gateways. This maximum is the sum of 255 interior neighbors plus 255 exterior neighbors from the two 8-bit fields in the EGP update message. EGP will not translate any reachability information for gateways beyond 510, and information on networks reachable through the 511th gateway and above will be lost. BGP, on the other hand, is not subject to this limit of 510 gateways. The Butterfly Mailbridges do not support BGP. Efforts are underway to replace the Mailbridges with the T/20, which DOES support both EGP and BGP, as core route servers. The replacement will be completed by June of 1993. The T/20 is capable of supporting both BGP2 and BGP3, and it will also do version negotiation. The details of the T/20 deployment as route servers will be given in a separate Management Bulletin. In anticipation of reaching the 510-gateway limit, it is crucial that MILNET subscriber gateways have BGP functionality before September of 1993. This may require software upgrades for some gateways. DISA will establish a user testing capability no later than 1 Apr 93. As soon as possible, DISA will provide a telephone contact for user testing. 3. BGP performs essentially the same function as EGP, i.e., it enables the exchange of routing information between gateways in different autonomous systems. A significant operational difference between BGP and EGP is that EGP updates contain the entire routing table information of the sending gateway, while BGP updates contain only the CHANGES in the sending gateway's routing table information. Once BGP has been fully deployed, the result will be a substantial decrease in the amount of overhead traffic carrying routing table information on the MILNET. 4. BGP currently exists in two versions (versions 2 and 3); T/20 is compatible with both. There is very little difference between BGP 2 and BGP 3, especially in the implmentations in the CISCOs and T/20 routers. BGP 4, however, is quite different from the previous versions and is NOT yet supported in the T/20s. If the vendor supports only BGP 4 and does not negotiate versions, the T/20 router servers will not work. Existing implementations of the various versions of BGP in CISCO and other vendor systems are available for the following versions of software: BGP 1 BGP 2 BGP 3 BGP 4 ----- ----- ----- ----- CISCO ----- 8.3 9.0.2* ?? GateD Gated 2.1 GateD 3.0Alpha GateD 3.0Alpha Summer, 1993 Proteon ----- ----- ---** April, 1993 3-Com ----- ----- Summer, 1993 * BGP 3 is available in release 9.0. Depending on your configuration requirments, 9.0.2 may be a more bug-free version. ** Per Proteon, their implementation of BGP4 will be backward compatible with, and will support version negotiation with, BGP 3. If your gateway is not a CISCO or a GateD system, check with your gateway vendor to determine which software version will support BGP. You should also determine if your hardware platform will be able to support the software release. NOTE: There is an operational problem with the use of BGP. The BGP 2 and 3 specifications have a feature that is not required for implementation specifying net 0.0.0.0 as the dynamic default route. MILNET core router service depends on the BGP implementation in both BBN T/20 routers and CISCO routers. The dynamic default route is not supported by any CISCO software releases supporting BGP, including the current release (9.0.3). In fact, if a 0.0.0.0 address is provided to a CISCO router in a BGP update, the BGP session on the router will fail. CISCO intends to correct this problem and implement the dynamic default route in release 9.0.4.1. This correction is also scheduled for release 9.1.3. DISA does not have release dates for these CISCO software versions. However, DISA believes these software releases will be available before the MILNET gateway count exceeds 510. In order to best manage this situation, DISA intends to deploy the T/20s and continue use of EGP as long as necessary. 5. Once the conversion to BGP begins, configuration changes in the subscriber gateways will be confined to activating a BGP rather than an EGP process and to selecting new primary and secondary Internet Route Servers (now T/20s rather than Mailbridges) at different IP addresses than are currently used by the Mailbridges. Details concerning the new server addresses and the gateways that have been assigned to these new servers will be contained in forthcoming DDN management bulletins. 6. If gateways do not switch from BGP to EGP, they can continue to do EGP with the T/20s and to receive routing table information from the T/20s in the same fashion as they currently do from the Mailbridges. However, if the number of gateways on the MILNET exceeds 510, EGP updates received by the non-BGP subscribers will be incomplete because gateways above the 510 count will simply be dropped from the update. This will result in gaps in the subscriber gateway's routing table, thus causing greater use of default routers and an overall decrease in network efficiency. 7. If you have any questions concerning BGP, please contact Maj Tatchio -- DSN: 222-2757 Com'l: (703) 692-2757, email: milnetmgr@ddn-conus.ddn.mil