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RSVP
Issue 6 January 2008 323
policy. The TOS byte is an OSI model Layer 3 solution, and works on IP packets on the LAN
and possibly the WAN, depending upon the service provider.
RSVP
Resource Reservation Protocol (RSVP) is a protocol that hosts can use to request specific QoS
parameters through the network for a particular application data stream. A host can request
guaranteed service through a network. If all routers have RSVP support enabled, and if there
exists sufficient unreserved bandwidth, a reservation is established throughout the network. If
insufficient bandwidth exists, the reservation fails and notifies the hosts. At that point, hosts can
choose to send traffic without a reservation, or drop the connection.
RSVP is supported in Communication Manager beginning with Release 1.3. RSVP can be
enabled per network region on the network region form. If RSVP is enabled, endpoints including
IP Telephones and media processors attempt to establish a reservation for each call. If the
reservation fails, Avaya endpoints still try to place a call, but lower the DiffServ priority of the call
Table 55: Original TOS specification
Bit
description
Value Use
Bits 0-2IP
precedence
000
001
010
011
100
101
110
111
Routine
Priority
Immediate
Flash
Flash Override
CRITIC/ECP
Internetwork control
Network control
Bit 3
delay
0
1
Normal
Low
Bit 4
Throughput
0
1
Normal
High
Bit 5
reliability
0
1
Normal
High
Bit 6
monetary cost
0
1
Normal
Low
Bit 7
reserved
Always set to 0