Transport layer of the OSI model

GHOSTRIDER2016

Guys,

I have been having a look at the OSI model and what I find perplexing is that. Apparently end to end transmission occurrs at the transport layer. So am i right in saying that the packet will be encapsulated with the the appropriate headers in the datalink and network layers then the sole function of the transport layer is to get that newly wrapped up packet to the destination machine ? using the mac address and ip address headers.

Thanks

FillAwful

I Think of it like this: As you go up the the OSI stack you peel away layers of the packet from outer to inner frames (wireshark illustrates this well). The transport layer is concerned with Transport Protocols like TCP and UDP.

When a packet traverses a network the packets are read or changed, or even stripped away, by devices (routers, switches and firewalls) outside to inside.

Layer 2 Data link (ARP, Mac address) read by the switch, to the router (Network Layer) IPv4, IPv6, to the firewall (Transport layer, Ports) and finally to the different application layers (Session data and application data like SSL, HTTP, DNS). The reverse process for incoming packets.

Hope this helps.

amcnow

To sum things up, encapsulation (i.e., adding headers and/or footers) occurs when moving down the OSI stack. Decapsulation (i.e., stripping headers and/or footers) occurs when moving back up the OSI stack.