transport layer
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... Internet protocol
suite. This RFC covers the communication protocol layers: link
layer, IP layer, and transport layer. Its companion RFC,
"Requirements for Internet ...
... reliability is implemented in the hosts, in the
transport layer or in application programs. All
connection control information is thus co-located ...
... Transport Layer ...
... services for applications. There are two primary
transport layer protocols at present:
...
...
Transport layer protocols are discussed in Chapter 4.
...
... internet layer, and
the transport layer, respectively. A companion RFC [INTRO:1]
covers application level software. This layerist organization
...
... implied by these calls, but need not literally implement the
calls themselves. For example, many implementations reflect
the coupling between the transport layer and the IP layer by
giving them shared access to common data structures ...
... In this description of the lower-layer protocols, a
message is the unit of transmission in a transport layer
protocol. In particular, a TCP segment is a message. A
...
... IP datagram consists of an IP header
followed by transport layer data, i.e., of an IP header
followed by a message.
...
... cache entry.
This call would be analogous to the
"ADVISE_DELIVPROB()" call from the transport layer
to the Internet layer ...
... passes the encapsulated message to the appropriate
transport-layer protocol module. ...
... sets any fields not set by the transport layer; ...
... section. This validation could be done in either the IP
layer or by each protocol in the transport layer.
...
...
The IP layer MUST provide a means for the transport layer to
set the TOS field of every datagram ...
...
TOS values up to the transport layer.
...
...
The IP layer MUST provide a means for the transport layer to
set the TTL field of every datagram ...
...
There MUST be a means for the transport layer to specify IP
options to be included in transmitted IP datagrams (see
...
... IP options (except NOP or END-OF-LIST) received in
datagrams MUST be passed to the transport layer (or to ICMP
processing when the datagram is an ICMP message ...
... ICMP message). The IP
and transport layer MUST each interpret those IP options
that they understand and silently ignore the others.
...
...
Passing all received IP options to the transport layer
is a deliberate "violation of strict layering" that is
designed to ease the introduction of new transport ...
... the option as received (the recorded route) MUST be
passed up to the transport layer (or to ICMP message
processing). This recorded route ...
... timestamp to a Timestamp option before
passing the option to the transport layer or to
ICMP for processing.
...
... layer is required to pass an
ICMP error message to the transport layer, the IP protocol
number MUST be extracted from the original header and used to
...
... A Destination Unreachable message that is received MUST be
reported to the transport layer. The transport layer SHOULD
use the information appropriately; for example, see Sections
...
... Destination Unreachable message that is received MUST be
reported to the transport layer. The transport layer SHOULD
use the information appropriately; for example, see Sections
4.1.3.3, 4.2.3.9, and 4.2.4 below. A transport protocol ...
... If a Source Quench message is received, the IP layer MUST
report it to the transport layer (or ICMP processing). In
general, the transport ...
... transmission rate again. The mechanism to respond to
Source Quench may be in the transport layer (for
connection-oriented protocols like TCP ...
... An incoming Time Exceeded message MUST be passed to the
transport layer.
...
... incoming Parameter Problem message MUST be passed to the
transport layer, and it MAY be reported to the user.
...
... needs to detect a failed first-hop gateway quickly
enough that transport-layer connections will not break
before an alternate gateway ...
...
There MUST be a mechanism by which the transport layer can
learn MMS_R, the maximum message size ...
...
A host MUST implement a mechanism to allow the transport layer
to learn MMS_S, the maximum transport-layer ...
... transport layer
to learn MMS_S, the maximum transport-layer message size that
may be sent for a given {source, destination ...
... IP reserves space to insert IP options for its own purposes
in addition to any options inserted by the transport layer.
...
... host that does not implement local fragmentation MUST ensure
that the transport layer (for TCP) or the application layer
...
... transport protocol
may send; even when MMS_S exceeds 556, the transport
layer must limit its messages to 556 bytes in the
absence of other knowledge about the destination
host.
...
... a UDP-based query), the transport layer on a multihomed
host needs to know which source address ...
... host needs to know which source address to use. If the
application does not specify it, the transport layer
must ask the IP layer to perform the conceptual
...
... The interface between the IP layer and the transport layer MUST
provide full access to all the mechanisms of the IP layer,
...
... Type-of-Service, and Time-to-Live. The
transport layer MUST either have mechanisms to set these interface
parameters, or provide a path to pass them through from an
...
...
We now describe a conceptual interface between the transport layer
and the IP layer, as a set of procedure calls. This is an
...
... IP options received in the
datagram; these MUST also be passed to the transport layer.
* Select Source Address ...
... Passing an Id parameter is optional; see Section 3.2.1.5.
The transport layer MUST be able to send certain ICMP
messages: Port Unreachable or any of the query ...
... IP layer MUST pass certain ICMP messages up to the
appropriate transport-layer routine. This function could be
considered to be a special case of the RECV() call, of
course; we describe it separately for clarity.
...
... the original message that are included in the ICMP message.
This data will be used by the transport layer to locate the
connection state ...
... | | | | | | |
TOS: | | | | | | |
Allow transport layer to set TOS |3.2.1.6 |x| | | | |
Pass received TOS ...
... TOS |3.2.1.6 |x| | | | |
Pass received TOS up to transport layer |3.2.1.6 | |x| | | |
Use RFC-795 link-layer ...
... Discard received packets with TTL < 2 |3.2.1.7 | | | | |x|
Allow transport layer to set TTL |3.2.1.7 |x| | | | |
Fixed TTL ...
... | | | | | | |
IP Options: | | | | | | |
Allow transport layer to send IP options |3.2.1.8 |x| | | | |
Pass all IP options ...
... datagrams |3.3.2 |x| | | | |
EMTU_R configurable or indefinite |3.3.2 | |x| | | |
Transport layer able to learn MMS_R |3.3.2 |x| | | | |
Send ICMP ...
... | | | | | | |
INTERFACE: | | | | | | |
Allow transport layer to use all IP mechanisms |3.4 |x| | | | |
Pass interface ...
... IP mechanisms |3.4 |x| | | | |
Pass interface ident up to transport layer |3.4 |x| | | | |
Pass all IP options up to transport layer ...
... transport layer |3.4 |x| | | | |
Pass all IP options up to transport layer |3.4 |x| | | | |
Transport layer can send certain ICMP messages ...
... IP options up to transport layer |3.4 |x| | | | |
Transport layer can send certain ICMP messages |3.4 |x| | | | |
Pass spec'd ICMP messages ...
...
where MMS_R is the maximum size for a transport-layer
message that can be received (and reassembled). TCP obtains
...