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Cisco WAN Manager User’s Guide
Version 10.5, Part Number 78-12945-01 Rev. D0, August 2003
Appendix A Internet Connec tivity
SVC Connections
specifies which SVC on the rou ter s h o ul d be use d. Th e ATM interface o n th e r o ut er, if u s in g LLC
encapsulation as described in RFC1 48 3, prefixes the data with a header that specifies to the remo te en d
of the SVC that the data is encapsulated IP data. The router then transmits the data onto the SVC.
The encapsulated IP data is received by the MGX 8850 Release 2 IPATM interface on one of its router
SVCs. Using RFC1483 if the data is on an SVC supporting LLC encapsulation, IPATM interface strips
off the prefixed header and verifies that the data is truly IP data. If it is, the IPATM interface performs a
very important function: it ad ds an entry to a local cache to rememb er w h ic h SVC was used by the IP
host/workstation to reach the M G X 8 850 Re lease 2. The cache has the following f orm at :
•IP Address of IP host/workstation
•SVC VC identifier that data was received on
•Timer to be used to time-out the cache entry for the IP host/workstation
Should the cache entry already exist for the IP host/workstation it is updated if the SVC being used has
changed. This allows the IPATM interface to dynamically ch o ose th e correct SVC necessary. After
setting up the cache entry, IPATM interface then adds a new VxWorks IP host-r o ute f o r th e I P
host/workstation. The IP ho st-route will allow VxWorks IP stack to give a ll IP data that is to be sent to
the IP host/workstation to the IPATM interface. Once the IP host-route is set up, the IPATM interface
gives the received IP data to VxWorks IP layer. From th er e, i t wi ll b e r o uted to t he appropriate server
application of the MGX 8850 Release 2.
Should the server applicatio n of the MGX 8850 Release 2 need to respond to the data received from the
IP host/workstation, it will do so by making a client/server API call to VxWorks. The data from the
server will eventually reach the VxWorks IP layer, where a IP route table w ill be sear c hed to det er min e
the correct interface that shou l d be used for the transmission . T he V x Works IP lay er will find the IP
host-route that was previously added by the IPATM interface when the data was originally received and
the data will be given to IPATM.
The IPATM interface, when given IP data from VxWorks IP layer, will pe rfo rm a cache lookup of the
destination IP address of the d ata . In the cache, an entry should exist that specifies which SVC VC
identifier should be used for sendi ng the IP data. If found, the data is prefixed with a header as described
by RFC1483 if the SVC supports LLC encapsula tion and sent. If not, the data is dropped and a statistic
is kept for the dropped data.
The router will receive the data tran s mit ted by t he I PATM interface, strip the RF C 1 48 3 h ead er i f
required, and transmit the da ta to the correct IP interface for r ea c h in g th e I P h o st/w o rk s ta ti on . A g ain ,
this will be accomplished using a IP route table lookup in the router.
The IP host/workstation will receive the data transm itted by the MGX 8850 Release 2 server and forward
the data to the appropriate TCP/IP client running on the host/workstation.
SVC Connections
To configure the type of ne tw or k a s s h ow n in Figure A-1, you must first create an SVC connection
between an MGX 8850 Release 2 node (MGX 8850 C) and a router (CWM RTR-1). Configure the
connection to MGX 8850 C as your CWM gat ewa y . Ne xt, co nfi gure S VC connec tions betwee n the CWM
router and each of the other MGX 8850s.
The following two sections provide information about amp le configurations and the fea tures they offer.