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2.1.2.1.5 Echo Request

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An echo request is used in the proxy discovery protocol sequence. The header fields for an echo request are as follows:

Method: MUST be set to either the "RPC_IN_DATA" or the "RPC_OUT_DATA" string. Both are valid. The client SHOULD use "RPC_IN_DATA" when it is sending an echo request as part of a protocol sequence associated with IN channels and SHOULD use "RPC_OUT_DATA" when it is sending an echo request as part of a protocol sequence associated with OUT channels. If the client sends "RPC_IN_DATA" in this field, the proxy MUST act as inbound proxy. If the client sends "RPC_OUT_DATA" in this field, the proxy MUST act as outbound proxy.

Accept: Clients SHOULD set this to the "application/rpc" string literal. Inbound and outbound proxies MUST ignore this header field.

Cache-Control: Clients MUST set this to "no-cache". Inbound and outbound proxies MUST ignore this header field.

Connection: Clients SHOULD set this to Keep-Alive. Inbound and outbound proxies MUST ignore this header field.

Content-Length: Clients MUST set this header field to a value in the inclusive range of 0 to 0x10.<11>

Host: Clients MUST set this to the server name of the inbound or outbound proxies as specified in [RFC2616] section 14.23, Host. Inbound and outbound proxies SHOULD ignore this header field.

Pragma Directives:

  • Clients MUST add a "No-cache" pragma directive as specified in [RFC2616] section 14.32. Inbound and outbound proxies MUST ignore this directive.

Protocol: Clients SHOULD set this to 1.0. Inbound and outbound proxies SHOULD ignore this header field.

URL: The server name and port are encoded in this field. For information on how the encoding is done, see section 2.2.2.

User-Agent: Clients SHOULD set this to the "MSRPC" string literal. Inbound and outbound proxies SHOULD ignore this header field.

Message Body: Clients MAY set the message body to random content they choose as specified in [RFC2616].<12> Inbound and outbound proxies MUST ignore the message body.