480
A
PPENDIX
D: C
ONNE
X
TIONS
H.323 G
ATEWAY
The second part of the 802.1(p and q) standards addresses the way LAN
switches prioritize different packets that are competing to enter a
different LAN segment. This scheme is based on a 3-bit priority field
within the Ethernet header.
NBX ConneXtions does not support the Layer 2 (Ethernet) 802.1 (
p and q
)
priority field. However, it is usually possible for IP routers to use these
priority schemes if they are configured to prioritize H.323 packets.
Layer 3
NBX systems address Layer 3 priority concerns through a
packet priority scheme called “IP/DS” (for differentiated services). Many
routers support this scheme, which replaces an earlier scheme (TOS),
which uses a 6-bit priority field within the IP header of every packet. Most
routers examine this field and base their pass-through priorities on it.
NBX systems are designed to use the default values that come with 3Com
switches. If you use other routers, you might need to reprogram their
diff-serv settings. The 3Com default is 101110xx. This setting must be
consistent at both ends of the connection. Note that some routers
overwrite the TOS field (diff-serv priority field) and eliminate the priority
distinctions between packets.
NBX ConneXtions does not support the Layer 3 (IP) 6-bit TOS/DS priority
field. However, it is usually possible for IP routers to use these priority
schemes if they are configured to prioritize H.323 packets.
Special Issues
This section describes issues related to H.323 telephony in general and to
ConneXtions gateways in particular. These include:
■
Firewall Security
■
Gateway Load
■
Remote Access
■
PBX Connections
■
Class of Service
■
IP Type of Service and Differentiated Services
■
Alternate Gatekeepers
Firewall Security
Firewalls determine which packets can cross the boundary between a
protected network (intranet) and the public internet. The network
Содержание 3C10402B
Страница 18: ...18 ...
Страница 22: ...22 ABOUT THIS GUIDE ...
Страница 26: ...26 CHAPTER 1 INTRODUCTION ...
Страница 74: ...74 CHAPTER 3 FEATURE SETTINGS ...
Страница 130: ...130 CHAPTER 5 TELEPHONE CONFIGURATION ...
Страница 156: ...156 CHAPTER 7 CALL DISTRIBUTION GROUPS ...
Страница 194: ...194 CHAPTER 8 PSTN GATEWAY CONFIGURATION ...
Страница 256: ...256 CHAPTER 10 SIP MODE OPERATIONS ...
Страница 328: ...328 CHAPTER 11 DIAL PLAN ...
Страница 360: ...360 CHAPTER 13 DOWNLOADS ...
Страница 370: ...370 CHAPTER 14 LICENSING AND UPGRADES ...
Страница 406: ...406 CHAPTER 16 NETWORK MANAGEMENT ...
Страница 412: ...412 CHAPTER 17 COUNTRY SETTINGS ...
Страница 450: ...450 APPENDIX A INTEGRATING THIRD PARTY MESSAGING ...
Страница 456: ...456 APPENDIX B ISDN COMPLETION CAUSE CODES ...
Страница 510: ...510 APPENDIX F OUTBOUND CALLER ID AND 911 SERVICE ...
Страница 546: ...546 APPENDIX G NBX ENTERPRISE MIB ...
Страница 566: ...566 GLOSSARY ...
Страница 578: ...578 INDEX ...
Страница 582: ......