A host uses the TCP maximum segment size option to specify the max size of TCP segments (packets) that it can accept. In the case where you have the slow response time, the mainframe is saying that its max segment size is 4056 bytes, which means that it can accept packets of that size (with that much payload). This is somewhat non-standard, but I doubt it would cause slow response time.
Does the client really try to send such large packets? I doubt it. But that's what you need to look at. How does the client react to the mainframe saying that its MSS is 4056 bytes. If the client is on Ethernet, it can't send such large packets. Also, what sort of PC/mainframe application would try to send such large frames? Most such applications would use much smaller packets. So I doubt that the MSS is the problem.... The major difference that stands out for the case where there's slow versus good respons time is that the slow response is on a site-to-site VPN link and the fast response is on a Frame Relay WAN. What are the speeds of the two links? I'm not a VPN expert, but I know that VPNs have a lot of overhead and can be slow. Where is the tunneling and encryption happening? Are the devices that are doing that slow? If I were you, I would consider the MSS a misleading clue and focus on telling us more about this slow VPN link. Thanks, Priscilla kuma kk wrote: > > Hello group, > > I am facing slow response issue when connecting to Mainframe. > This is how my > connectivity goes > > [EMAIL PROTECTED] A ---> FrameRelay(WAN) --> Location B ---> Site to > Site VPN (T1) > --> [EMAIL PROTECTED] C > > I have captured the packet using ethereal and found that Source > PC TCP > Maximum Segment Size is 1456bytes and that of Mainframe is > 4056bytes. This > slow response issue with mainframe is intermittent. And there > is no issue at > the mainframe as it works fine when I connect from within the > Location C > > Source side there is no issue since for some other mainframe at > Location D, > I am getting good response and the Source PC MSS is 1456bytes > and that of > Mainframe MSS is 536bytes. The only difference in this > connectivity is that > this mainframe is connected using an framerealy from Location B > to Location > D (given below) > > [EMAIL PROTECTED] A ---> FrameRelay(WAN) --> Location B ---> > FrameRelay(WAN)--> > [EMAIL PROTECTED] D > > I would like to know whether the MSS Size of 4056bytes from > mainframe in the > Location C attributes to the slow reponse issue. Is the high > MSS size is due > to Site-to Site VPN from Location B to C( due to excess header > information > due to VPN) or something else. > > Would appreciate your response. > > TIA, > Kum > > _________________________________________________________________ > Design your holidays. At your convenience. > http://www.flexihols.com/2003/index.php Click here. > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=72033&t=72030 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
