Cisco IOS can send Path and Resv messages on behalf of clients. This proxy capability is useful for testing RSVP when you don't have any RSVP-enabled clients available. Figure 5-8 depicts such a scenario.
Figure 5-8 Router A Can Proxy Path Messages for a Non-RSVP Client (Client A)
Client A (sender) 192.168.20.1
non-RSVP
Client B (receiver) 192.168.10.2
non-RSVP
Router A E0
S0 10.1.1.1
Router B S0
E0 10.1.1.2 PATH Simulated
PATH Propagated downstream
PATH
Client A does not support RSVP, so it cannot generate any Path messages and send them to the network. For the purpose of testing RSVP, you can configure Router A to proxy for Client A and send Path messages to the network on Client A's behalf. Other devices in the network then interpret the Path messages as originating from Client A, even though they are actually sourced by Router A.
To enable the proxy function, you configure one or more static RSVP senders on Router A. This causes Router A to generate Path messages and forward them downstream as normal RSVP Path messages. While Path messages are flowing, you can verify the mechanics of RSVP by observing what happens on Router A and other devices in the network.
The ip rsvp sender command (global configuration mode) configures a static RSVP sender.
The following example coincides with Figure 5-8 and configures a static sender on Router A:
ip rsvp sender 192.168.10.2 192.168.20.1 TCP 0 0 192.168.20.1 Et0 10 5
The preceding command configures all the data that make up a Path message:
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The first IP address (192.168.10.2) is the receiver's address (Client B). The receiver can be an IP multicast address for multicast sessions. The second IP address (192.168.20.1) is the sender's IP address (Client A).•
Next, TCP tells the router that this is a TCP session. Alternatively, you can configure UDP or an IP protocol number.•
The two zeros tell the router to ignore the source and destination TCP port numbers when it considers packets part of this session. If you want the reservation to apply to a specific TCP session (instead of any TCP session from the sender), configure the destination port number in place of the first zero and the source port number in place of the second zero.•
The next entry is the previous hop address and is part of a standard RSVP Path message.The previous hop is the router that is one hop upstream in the direction of the sender; in this case, the upstream hop is the sender itself (Client A). In a different network, it could be an upstream router.
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Et0 (Ethernet0) is the interface on this router that points to the previous hop.•
Finally, the last two numbers are descriptions of the session flow itself. This session is configured for a bandwidth of 10 kbps with a burst of 5000 bytes. The burst is the number of bytes that should be held in a queue when traffic from a session exceeds 10 kbps.With Router A generating Path messages on behalf of Client A, you can verify that Router B is receiving them. Issuing the command show ip rsvp sender on Router B confirms that Router B (the downstream router) is receiving the static Path message configured on Router A:
RTB#sh ip rsvp sender
To From Pro DPort Sport Prev Hop I/F BPS Bytes 192.168.10.2 192.168.20.1 TCP 0 0 10.1.1.1 Se0 10K 5K
In the preceding output, the To column is the receiver's address and the From column is the sender's address. The previous hop address is 10.1.1.1 (Router A), and Serial0 (Se0) is the interface that points to the previous hop. The other fields match the parameters of the static sender configured on Router A (protocol, ports, bandwidth, and burst).
In addition to Path messages, you can also proxy Resv messages with IOS. To proxy Resv messages on a router, configure one or more static RSVP receivers with the ip rsvp reservation global configuration command. The following line is configured in Router B, which is downstream of Router A (refer to Figure 5-8 for the topology):
ip rsvp reservation 192.168.10.2 192.168.20.1 TCP 0 0 192.168.10.2 Et0 FF RATE 10 5
Note the following in this configuration:
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The first IP address (192.168.10.2) is the receiver's address (Client B). The second IP address (192.168.20.1) is the sender's IP address (Client A).•
TCP tells the router that this is a TCP session. Alternatively, you can configure UDP or an IP protocol number.•
The two zeros tell the router to ignore the source and destination TCP port numbers when it considers packets part of this session. If you want the reservation to apply to a specific TCP session (instead of any TCP session from the sender), configure the destination port number instead of the first zero and the source port number instead of the second zero.•
The next entry is called the next hop address and is part of a standard RSVP Resv message.The next hop is the router that is one hop downstream in the direction of the receiver. In this example, the downstream hop is the receiver itself (Client B); in a different network, it could be a downstream router.
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Et0 (Ethernet0) is the interface on this router that points to the next hop.•
FF stands for fixed filter and is an RSVP reservation style. Reservations can be dedicated to a single sender or shared by multiple senders. A reservation for a single sender is a fixed filter reservation, whereas a reservation shared by multiple senders is either a wildcard filter (WF) or a shared explicit (SE) reservation. For the purpose of testing, the fixed filter style should suffice.NOTE A WF reservation is shared by all upstream senders, but an SE reservation is shared by a selected group of upstream senders. Consult RFC 2205 for more information.
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RATE 10 5 defines the QoS that is requested by the receiver in the Resv message. This example requests bandwidth of 10 kbps and a burst size of 5000 bytes.With Router B configured to send Resv messages upstream on behalf of Client B, you can verify that Router A is receiving those messages. Issuing the command show ip rsvp request on Router A confirms that Router A (the upstream router) is receiving the static Resv message configured on Router B:
RTA#sh ip rsvp request
To From Pro DPort Sport Next Hop I/F Fi Serv BPS Bytes 192.168.10.2 192.168.20.1 TCP 0 0 10.1.1.2 Se0 FF RATE 10K 5K
In the preceding output, the To column is the receiver's address and the From column is the sender's address. The next hop address is 10.1.1.2 (Router B), and Serial0 (Se0) is the interface that points to the next hop. The other fields match the parameters of the static receiver configured on Router B (protocol, ports, style, bandwidth, and burst).
After the Path and Resv messages are flowing and the configured reservation is in place (confirm with the allocate column of show ip rsvp interface), you can test the QoS throughput and latency over the reserved path from sender to receiver.
TIP Use the debug ip rsvp enable mode command to observe the Path and Resv messages generated by your routers.