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Home > Archive > CCNA > April 2002 > Question on Connection-oriented/reliable Protocols.
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Question on Connection-oriented/reliable Protocols.
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| lawnwezza 2002-04-15, 12:37 pm |
| Cisco Press has it that a connection-oriented protocols needs not compulsorily provide error recovery and vice-versa.
It said that for a protocol to be connection-oriented, there must be pre-transmission exchange of messages or a predefined correlation b/w the transmitting and recieving devices. For that, Frame-Relay PVC are connection oriented, but they are unreliable since there is no retransmission or error recovery mechanism.
It also listed Frame-relay SVC as connectionless but reliable. How is it so? What mechanism does Frame-relay SVC have that makes it reliable? Can someone kindly put me through.
Thanks  | |
| haseeb_eng 2002-04-16, 1:19 am |
| Frame relay is a layer 2 protocol . PVC & SVC are not protocols , these are just virtual circuits which frame relay uses . frame relay is not reliable but data reliability has been made on tcp(which is connection oriented) because anyway data has to come from layer2 to layer4 .
Haseeb  | |
| shashankvaidya 2002-04-16, 8:41 am |
| 1) Frame Relay is purely Layer 2 protocol.
2) FR assumes the links are less error prone.
3) FR uses FECN & BECN events to prevent the congestion in the n/w.
4) FR uses SVC which establishes the connections whenever required prior to actual data transmission. And PVC which is always established.
Hope this is correct
Rgds
SV
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| lawnwezza 2002-04-16, 12:29 pm |
| Haseeb, you are quite in order, but you should realise that when the issue of connection-oriented/connectionless protocol is discussed, emphasis is not solely on layer 4. PPP, for instance, is layer 2 but connection-oriented. Moreover, you are under the assumption that Frame-relay would always use tcp/ip, assuming it doesn't? Suppose it use spx/ipx. Here, the protocols should be considered in isolation.
shashankvaidya, from 4. of your post, frame-relay, whether implimenting SVC or PVC is connection-oriented. Table 3-4 pg 88 of Odom's book is very illogical and very confusing. Someone check it out.
Pls, more clearification is needed
Haseeb and shashankvaidya, thanks for your contributions.They were informative.
Lawnwezza | |
| lawnwezza 2002-04-16, 12:40 pm |
| Haseeb, you are quite in order, but you should realise that when the issue of connection-oriented/connectionless protocol is discussed, emphasis is not solely on layer 4. PPP, for instance, is layer 2 but connection-oriented. Moreover, you are under the assumption that Frame-relay would always use tcp/ip, assuming it doesn't? Suppose it use spx/ipx. Here, the protocols should be considered in isolation.
shashankvaidya, from 4. of your post, frame-relay, whether implimenting SVC or PVC is connection-oriented. Table 3-4 pg 88 of Odom's book is very illogical and very confusing. Someone check it out.
Pls, more clearification is needed
Haseeb and shashankvaidya, thanks for your contributions.They were informative.
Lawnwezza | |
| lawnwezza 2002-04-16, 1:54 pm |
| Haseeb, you are quite in order, but you should realise that when the issue of connection-oriented/connectionless protocol is discussed, emphasis is not solely on layer 4. PPP, for instance, is layer 2 but connection-oriented. Moreover, you are under the assumption that Frame-relay would always use tcp/ip, assuming it doesn't? Suppose it use spx/ipx. Here, the protocols should be considered in isolation.
shashankvaidya, from 4. of your post, frame-relay, whether implimenting SVC or PVC is connection-oriented. Table 3-4 pg 88 of Odom's book is very illogical and very confusing. Someone check it out.
Pls, more clearification is needed
Haseeb and shashankvaidya, thanks for your contributions.They were informative.
Lawnwezza | |
| shashankvaidya 2002-04-17, 4:00 am |
| Yes,
FR is connection-oriented thru Data link layer via virtual circuits.
SVC :- Are like telephone calls or ISDN
PVC :- Are like HotLines (Always connected.)or Leased circuits.
Refer to frforum.com,which has given fr in detail.
Abt Odom's book, don't have, but there could be typographic mistake.
rgds
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| WarRoom 2002-04-18, 10:47 pm |
| shashankvaidya has a good analogy with the phone idea. Frame Relay uses the call setup, data transfer, and call termination process. Routers place calls accross the Frame Relay network. After the call is established, the router transfers data and then closes the call (SVC). In the case of PVC's, the call is always active, allowing the router to send data without placeing the call. | |
| ROUTERRIP 2002-04-19, 5:49 pm |
| here it is... straight from my personal notes. gotta get organized if you want to pass test...
ERROR RECOVERY PROTOCOLS:
Connection-oriented: TCP, SPX, X.25, LLC type 2.
Connectionless: TFTP, Netware NCP.
Non-ERROR RECOVERY PROTOCOLS:
Connection-oriented: FR PVC’s, ATM PVC’s, and PPP.
Connectionless: UDP, IP, IPX, Apple DDP, 802.3/802.5. | |
| muckfish 2002-04-20, 3:09 am |
| lawnwezza,
i think the fact that virtual circuits (or a logical connection) are establised actually makes it connection oriented. Reliability is provided using an acknowledgement mechanism.
Connectionless communications do not set up virtual circuits. They just send the data to the receipient without any prior establishment of logical connections.
With respect to connectionless but reliable, i think it means that no logical connections are set up but acknowledgements are sent from the receipient to the sender once it has received data.
At any layer of the OSI you can provide connection oriented or connectionless protocols. Hope this helps! | |
| haseeb_eng 2002-04-20, 6:11 am |
| lawnwezza i think so you did not read my post well . I said that data will come from L2 to L4 . It does not matter either it is TCP or SPX because both are on L4 and reliable . | |
| lawnwezza 2002-04-20, 11:47 am |
| Thanks guys for the contribution. I think I am clear on a number of issues. You are all very wonderful.
lawnwezza  |
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